| Message ID | 20230825152425.2417656-3-qing.zhao@oracle.com |
|---|---|
| State | New |
| Headers | show |
| Series | New attribute "counted_by" to annotate bounds for C99 FAM(PR108896) | expand |
Ping. thanks. Qing > On Aug 25, 2023, at 11:24 AM, Qing Zhao <qing.zhao@oracle.com> wrote: > > Use the counted_by atribute info in builtin object size to compute the > subobject size for flexible array members. > > gcc/ChangeLog: > > PR C/108896 > * tree-object-size.cc (addr_object_size): Use the counted_by > attribute info. > * tree.cc (component_ref_has_counted_by_p): New function. > (component_ref_get_counted_by): New function. > * tree.h (component_ref_has_counted_by_p): New prototype. > (component_ref_get_counted_by): New prototype. > > gcc/testsuite/ChangeLog: > > PR C/108896 > * gcc.dg/flex-array-counted-by-2.c: New test. > * gcc.dg/flex-array-counted-by-3.c: New test. > --- > .../gcc.dg/flex-array-counted-by-2.c | 74 ++++++ > .../gcc.dg/flex-array-counted-by-3.c | 210 ++++++++++++++++++ > gcc/tree-object-size.cc | 37 ++- > gcc/tree.cc | 95 +++++++- > gcc/tree.h | 10 + > 5 files changed, 418 insertions(+), 8 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > > diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > new file mode 100644 > index 000000000000..ec580c1f1f01 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > @@ -0,0 +1,74 @@ > +/* test the attribute counted_by and its usage in > + * __builtin_dynamic_object_size. */ > +/* { dg-do run } */ > +/* { dg-options "-O2" } */ > + > +#include "builtin-object-size-common.h" > + > +#define expect(p, _v) do { \ > + size_t v = _v; \ > + if (p == v) \ > + __builtin_printf ("ok: %s == %zd\n", #p, p); \ > + else \ > + { \ > + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ > + FAIL (); \ > + } \ > +} while (0); > + > +struct flex { > + int b; > + int c[]; > +} *array_flex; > + > +struct annotated { > + int b; > + int c[] __attribute__ ((counted_by (b))); > +} *array_annotated; > + > +struct nested_annotated { > + struct { > + union { > + int b; > + float f; > + }; > + int n; > + }; > + int c[] __attribute__ ((counted_by (b))); > +} *array_nested_annotated; > + > +void __attribute__((__noinline__)) setup (int normal_count, int attr_count) > +{ > + array_flex > + = (struct flex *)malloc (sizeof (struct flex) > + + normal_count * sizeof (int)); > + array_flex->b = normal_count; > + > + array_annotated > + = (struct annotated *)malloc (sizeof (struct annotated) > + + attr_count * sizeof (int)); > + array_annotated->b = attr_count; > + > + array_nested_annotated > + = (struct nested_annotated *)malloc (sizeof (struct nested_annotated) > + + attr_count * sizeof (int)); > + array_nested_annotated->b = attr_count; > + > + return; > +} > + > +void __attribute__((__noinline__)) test () > +{ > + expect(__builtin_dynamic_object_size(array_flex->c, 1), -1); > + expect(__builtin_dynamic_object_size(array_annotated->c, 1), > + array_annotated->b * sizeof (int)); > + expect(__builtin_dynamic_object_size(array_nested_annotated->c, 1), > + array_nested_annotated->b * sizeof (int)); > +} > + > +int main(int argc, char *argv[]) > +{ > + setup (10,10); > + test (); > + DONE (); > +} > diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > new file mode 100644 > index 000000000000..a0c3cb88ec71 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > @@ -0,0 +1,210 @@ > +/* test the attribute counted_by and its usage in > +__builtin_dynamic_object_size: what's the correct behavior when the > +allocation size mismatched with the value of counted_by attribute? */ > +/* { dg-do run } */ > +/* { dg-options "-O -fstrict-flex-arrays=3" } */ > + > +#include "builtin-object-size-common.h" > + > +struct annotated { > + size_t foo; > + char others; > + char array[] __attribute__((counted_by (foo))); > +}; > + > +#define expect(p, _v) do { \ > + size_t v = _v; \ > + if (p == v) \ > + __builtin_printf ("ok: %s == %zd\n", #p, p); \ > + else \ > + { \ > + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ > + FAIL (); \ > + } \ > +} while (0); > + > +#define noinline __attribute__((__noinline__)) > +#define SIZE_BUMP 10 > +#define MAX(a, b) ((a) > (b) ? (a) : (b)) > +#define MIN(a, b) ((a) < (b) ? (a) : (b)) > + > +/* In general, Due to type casting, the type for the pointee of a pointer > + does not say anything about the object it points to, > + So, __builtin_object_size can not directly use the type of the pointee > + to decide the size of the object the pointer points to. > + > + there are only two reliable ways: > + A. observed allocations (call to the allocation functions in the routine) > + B. observed accesses (read or write access to the location of the > + pointer points to) > + > + that provide information about the type/existence of an object at > + the corresponding address. > + > + for A, we use the "alloc_size" attribute for the corresponding allocation > + functions to determine the object size; > + > + For B, we use the SIZE info of the TYPE attached to the corresponding access. > + (We treat counted_by attribute as a complement to the SIZE info of the TYPE > + for FMA) > + > + The only other way in C which ensures that a pointer actually points > + to an object of the correct type is 'static': > + > + void foo(struct P *p[static 1]); > + > + See https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624814.html > + for more details. */ > + > +/* in the following function, malloc allocated more space than the value > + of counted_by attribute. Then what's the correct behavior we expect > + the __builtin_dynamic_object_size should have for each of the cases? */ > + > +static struct annotated * noinline alloc_buf_more (size_t index) > +{ > + struct annotated *p; > + size_t allocated_size > + = MAX (sizeof (struct annotated), > + (__builtin_offsetof (struct annotated, array[0]) > + + (index + SIZE_BUMP) * sizeof (char))); > + p = (struct annotated *) malloc (allocated_size); > + > + p->foo = index; > + > + /*when checking the observed access p->array, we have info on both > + observered allocation and observed access, > + A. from observed allocation: > + allocated_size - offsetof (struct annotated, array[0]) > + B. from observed access: p->foo * sizeof (char) > + */ > + > + /* for size in the whole object: always uses A. */ > + /* for size in the sub-object: chose the smaller of A and B. > + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html > + * for details on why. */ > + > + /* for MAXIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 1), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /* for MINIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 2), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 3), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /*when checking the pointer p, we only have info on the observed allocation. > + So, the object size info can only been obtained from the call to malloc. > + for both MAXIMUM and MINIMUM: A = (index + SIZE_BUMP) * sizeof (char) */ > + expect(__builtin_dynamic_object_size(p, 0), allocated_size); > + expect(__builtin_dynamic_object_size(p, 1), allocated_size); > + expect(__builtin_dynamic_object_size(p, 2), allocated_size); > + expect(__builtin_dynamic_object_size(p, 3), allocated_size); > + return p; > +} > + > +/* in the following function, malloc allocated less space than the value > + of counted_by attribute. Then what's the correct behavior we expect > + the __builtin_dynamic_object_size should have for each of the cases? > + NOTE: this is an user error, GCC should issue warnings for such case. > + this is a seperate issue we should address later. */ > + > +static struct annotated * noinline alloc_buf_less (size_t index) > +{ > + struct annotated *p; > + size_t allocated_size > + = MAX (sizeof (struct annotated), > + (__builtin_offsetof (struct annotated, array[0]) > + + (index) * sizeof (char))); > + p = (struct annotated *) malloc (allocated_size); > + > + p->foo = index + SIZE_BUMP; > + > + /*when checking the observed access p->array, we have info on both > + observered allocation and observed access, > + A. from observed allocation: > + allocated_size - offsetof (struct annotated, array[0]) > + B. from observed access: p->foo * sizeof (char) > + */ > + > + /* for size in the whole object: always uses A. */ > + /* for size in the sub-object: chose the smaller of A and B. > + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html > + * for details on why. */ > + > + /* for MAXIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 1), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /* for MINIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 2), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 3), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /*when checking the pointer p, we only have info on the observed > + allocation. So, the object size info can only been obtained from > + the call to malloc. */ > + expect(__builtin_dynamic_object_size(p, 0), allocated_size); > + expect(__builtin_dynamic_object_size(p, 1), allocated_size); > + expect(__builtin_dynamic_object_size(p, 2), allocated_size); > + expect(__builtin_dynamic_object_size(p, 3), allocated_size); > + return p; > +} > + > +int main () > +{ > + struct annotated *p, *q; > + p = alloc_buf_more (10); > + q = alloc_buf_less (10); > + > + /*when checking the observed access p->array, we only have info on the > + observed access, i.e, the TYPE_SIZE info from the access. We don't have > + info on the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), -1); > + expect(__builtin_dynamic_object_size(p->array, 1), p->foo * sizeof(char)); > + expect(__builtin_dynamic_object_size(p->array, 2), 0); > + expect(__builtin_dynamic_object_size(p->array, 3), p->foo * sizeof(char)); > + /*when checking the pointer p, we have no observed allocation nor observed > + access, therefore, we cannot determine the size info here. */ > + expect(__builtin_dynamic_object_size(p, 0), -1); > + expect(__builtin_dynamic_object_size(p, 1), -1); > + expect(__builtin_dynamic_object_size(p, 2), 0); > + expect(__builtin_dynamic_object_size(p, 3), 0); > + > + /*when checking the observed access p->array, we only have info on the > + observed access, i.e, the TYPE_SIZE info from the access. We don't have > + info on the whole object. */ > + expect(__builtin_dynamic_object_size(q->array, 0), -1); > + expect(__builtin_dynamic_object_size(q->array, 1), q->foo * sizeof(char)); > + expect(__builtin_dynamic_object_size(q->array, 2), 0); > + expect(__builtin_dynamic_object_size(q->array, 3), q->foo * sizeof(char)); > + /*when checking the pointer p, we have no observed allocation nor observed > + access, therefore, we cannot determine the size info here. */ > + expect(__builtin_dynamic_object_size(q, 0), -1); > + expect(__builtin_dynamic_object_size(q, 1), -1); > + expect(__builtin_dynamic_object_size(q, 2), 0); > + expect(__builtin_dynamic_object_size(q, 3), 0); > + > + DONE (); > +} > diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc > index a62af0500563..cf7843c5684b 100644 > --- a/gcc/tree-object-size.cc > +++ b/gcc/tree-object-size.cc > @@ -585,6 +585,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > if (pt_var != TREE_OPERAND (ptr, 0)) > { > tree var; > + tree counted_by_ref = NULL_TREE; > > if (object_size_type & OST_SUBOBJECT) > { > @@ -600,11 +601,12 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > var = TREE_OPERAND (var, 0); > if (var != pt_var && TREE_CODE (var) == ARRAY_REF) > var = TREE_OPERAND (var, 0); > - if (! TYPE_SIZE_UNIT (TREE_TYPE (var)) > + if (! component_ref_has_counted_by_p (var) > + && ((! TYPE_SIZE_UNIT (TREE_TYPE (var)) > || ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var))) > || (pt_var_size && TREE_CODE (pt_var_size) == INTEGER_CST > && tree_int_cst_lt (pt_var_size, > - TYPE_SIZE_UNIT (TREE_TYPE (var))))) > + TYPE_SIZE_UNIT (TREE_TYPE (var))))))) > var = pt_var; > else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF) > { > @@ -612,6 +614,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > /* For &X->fld, compute object size if fld isn't a flexible array > member. */ > bool is_flexible_array_mem_ref = false; > + > while (v && v != pt_var) > switch (TREE_CODE (v)) > { > @@ -660,6 +663,8 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > /* Now the ref is to an array type. */ > gcc_assert (TREE_CODE (TREE_TYPE (v)) == ARRAY_TYPE); > is_flexible_array_mem_ref = array_ref_flexible_size_p (v); > + counted_by_ref = component_ref_get_counted_by (v); > + > while (v != pt_var && TREE_CODE (v) == COMPONENT_REF) > if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0))) > != UNION_TYPE > @@ -673,8 +678,11 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > == RECORD_TYPE) > { > /* compute object size only if v is not a > - flexible array member. */ > - if (!is_flexible_array_mem_ref) > + flexible array member or the flexible array member > + has a known element count indicated by the user > + through attribute counted_by. */ > + if (!is_flexible_array_mem_ref > + || counted_by_ref) > { > v = NULL_TREE; > break; > @@ -707,9 +715,24 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > > if (var != pt_var) > { > - var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); > - if (!TREE_CONSTANT (var_size)) > - var_size = get_or_create_ssa_default_def (cfun, var_size); > + if (!counted_by_ref) > + { > + var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); > + if (!TREE_CONSTANT (var_size)) > + var_size = get_or_create_ssa_default_def (cfun, var_size); > + } > + else > + { > + gcc_assert (TREE_CODE (var) == COMPONENT_REF > + && TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE); > + tree element_size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (var))); > + var_size > + = size_binop (MULT_EXPR, > + fold_convert (sizetype, counted_by_ref), > + fold_convert (sizetype, element_size)); > + if (!todo) > + todo = TODO_update_ssa_only_virtuals; > + } > if (!var_size) > return false; > } > diff --git a/gcc/tree.cc b/gcc/tree.cc > index fcd36ae0cd74..3b6ddcbdcbf8 100644 > --- a/gcc/tree.cc > +++ b/gcc/tree.cc > @@ -12745,6 +12745,32 @@ array_ref_element_size (tree exp) > return SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (elmt_type), exp); > } > > +/* For a component_ref that has an array type ARRAY_REF, return TRUE when > + an counted_by attribute attached to the corresponding FIELD_DECL. > + return FALSE otherwise. */ > +bool > +component_ref_has_counted_by_p (tree array_ref) > +{ > + if (TREE_CODE (array_ref) != COMPONENT_REF) > + return false; > + > + if (TREE_CODE (TREE_TYPE (array_ref)) != ARRAY_TYPE) > + return false; > + > + tree struct_object = TREE_OPERAND (array_ref, 0); > + tree struct_type = TREE_TYPE (struct_object); > + > + if (!RECORD_OR_UNION_TYPE_P (struct_type)) > + return false; > + tree field_decl = TREE_OPERAND (array_ref, 1); > + tree attr_counted_by = lookup_attribute ("counted_by", > + DECL_ATTRIBUTES (field_decl)); > + > + if (!attr_counted_by) > + return false; > + return true; > +} > + > /* Given a field list, FIELDLIST, of a structure/union, return a TREE_LIST, > with each TREE_VALUE a FIELD_DECL stepping down the chain to the FIELD > whose name is FIELDNAME, which is the last TREE_VALUE of the list. > @@ -12771,7 +12797,7 @@ get_named_field (tree fieldlist, const char *fieldname) > fields inside it recursively. */ > else if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (field))) > if ((named_field = get_named_field (TYPE_FIELDS (TREE_TYPE (field)), > - fieldname)) != NULL_TREE) > + fieldname)) != NULL_TREE) > { > named_field = tree_cons (NULL_TREE, field, named_field); > break; > @@ -12784,6 +12810,73 @@ get_named_field (tree fieldlist, const char *fieldname) > return named_field; > } > > +/* For a component_ref that has an array type ARRAY_REF, get the object that > + represents its counted_by per the attribute counted_by attached to > + the corresponding FIELD_DECL. return NULL_TREE when cannot find such > + object. > + For example, if: > + > + struct P { > + int k; > + int x[] __attribute__ ((counted_by (k))); > + } *p; > + > + for the following reference: > + > + p->x[b] > + > + the object that represents its element count will be: > + > + p->k > + > + So, when component_ref_get_counted_by (p->x[b]) is called, p->k should be > + returned. > +*/ > + > +tree > +component_ref_get_counted_by (tree array_ref) > +{ > + if (! component_ref_has_counted_by_p (array_ref)) > + return NULL_TREE; > + > + tree struct_object = TREE_OPERAND (array_ref, 0); > + tree struct_type = TREE_TYPE (struct_object); > + tree field_decl = TREE_OPERAND (array_ref, 1); > + tree attr_counted_by = lookup_attribute ("counted_by", > + DECL_ATTRIBUTES (field_decl)); > + gcc_assert (attr_counted_by); > + > + /* If there is an counted_by attribute attached to the field, > + get the field that maps to the counted_by. */ > + > + const char *fieldname > + = IDENTIFIER_POINTER (TREE_VALUE (TREE_VALUE (attr_counted_by))); > + > + tree counted_by_field = get_named_field (TYPE_FIELDS (struct_type), > + fieldname); > + > + gcc_assert (counted_by_field); > + > + /* generate the tree node that represent the counted_by of this array > + ref. This is a (possible nested) COMPONENT_REF to the counted_by_field > + of the containing structure. */ > + > + tree counted_by_ref = NULL_TREE; > + tree object = struct_object; > + do > + { > + tree field = TREE_VALUE (counted_by_field); > + > + counted_by_ref = build3 (COMPONENT_REF, > + TREE_TYPE (field), > + unshare_expr (object), field, > + NULL_TREE); > + object = counted_by_ref; > + counted_by_field = TREE_CHAIN (counted_by_field); > + } > + while (counted_by_field); > + return counted_by_ref; > +} > > /* Return a tree representing the lower bound of the array mentioned in > EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ > diff --git a/gcc/tree.h b/gcc/tree.h > index 4859becaa1e7..07eed7219835 100644 > --- a/gcc/tree.h > +++ b/gcc/tree.h > @@ -5619,11 +5619,21 @@ extern tree get_base_address (tree t); > of EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ > extern tree array_ref_element_size (tree); > > +/* Give a component_ref that has an array type, return true when an > + attribute counted_by attached to the corresponding FIELD_DECL. */ > +extern bool component_ref_has_counted_by_p (tree); > + > /* Given a field list, FIELDLIST, of a structure/union, return the FIELD whose > name is FIELDNAME, return NULL_TREE if such field is not found. > searching nested anonymous structure/union recursively. */ > extern tree get_named_field (tree, const char *); > > +/* Give a component_ref that has an array type, return the object that > + represents its counted_by per the attribute counted_by attached to > + the corresponding FIELD_DECL. return NULL_TREE when cannot find such > + object. */ > +extern tree component_ref_get_counted_by (tree); > + > /* Return a typenode for the "standard" C type with a given name. */ > extern tree get_typenode_from_name (const char *); > > -- > 2.31.1 >
Hi, I’d like to ping this patch set one more time. Thanks Qing > On Aug 25, 2023, at 11:24 AM, Qing Zhao <qing.zhao@oracle.com> wrote: > > Use the counted_by atribute info in builtin object size to compute the > subobject size for flexible array members. > > gcc/ChangeLog: > > PR C/108896 > * tree-object-size.cc (addr_object_size): Use the counted_by > attribute info. > * tree.cc (component_ref_has_counted_by_p): New function. > (component_ref_get_counted_by): New function. > * tree.h (component_ref_has_counted_by_p): New prototype. > (component_ref_get_counted_by): New prototype. > > gcc/testsuite/ChangeLog: > > PR C/108896 > * gcc.dg/flex-array-counted-by-2.c: New test. > * gcc.dg/flex-array-counted-by-3.c: New test. > --- > .../gcc.dg/flex-array-counted-by-2.c | 74 ++++++ > .../gcc.dg/flex-array-counted-by-3.c | 210 ++++++++++++++++++ > gcc/tree-object-size.cc | 37 ++- > gcc/tree.cc | 95 +++++++- > gcc/tree.h | 10 + > 5 files changed, 418 insertions(+), 8 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > > diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > new file mode 100644 > index 000000000000..ec580c1f1f01 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > @@ -0,0 +1,74 @@ > +/* test the attribute counted_by and its usage in > + * __builtin_dynamic_object_size. */ > +/* { dg-do run } */ > +/* { dg-options "-O2" } */ > + > +#include "builtin-object-size-common.h" > + > +#define expect(p, _v) do { \ > + size_t v = _v; \ > + if (p == v) \ > + __builtin_printf ("ok: %s == %zd\n", #p, p); \ > + else \ > + { \ > + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ > + FAIL (); \ > + } \ > +} while (0); > + > +struct flex { > + int b; > + int c[]; > +} *array_flex; > + > +struct annotated { > + int b; > + int c[] __attribute__ ((counted_by (b))); > +} *array_annotated; > + > +struct nested_annotated { > + struct { > + union { > + int b; > + float f; > + }; > + int n; > + }; > + int c[] __attribute__ ((counted_by (b))); > +} *array_nested_annotated; > + > +void __attribute__((__noinline__)) setup (int normal_count, int attr_count) > +{ > + array_flex > + = (struct flex *)malloc (sizeof (struct flex) > + + normal_count * sizeof (int)); > + array_flex->b = normal_count; > + > + array_annotated > + = (struct annotated *)malloc (sizeof (struct annotated) > + + attr_count * sizeof (int)); > + array_annotated->b = attr_count; > + > + array_nested_annotated > + = (struct nested_annotated *)malloc (sizeof (struct nested_annotated) > + + attr_count * sizeof (int)); > + array_nested_annotated->b = attr_count; > + > + return; > +} > + > +void __attribute__((__noinline__)) test () > +{ > + expect(__builtin_dynamic_object_size(array_flex->c, 1), -1); > + expect(__builtin_dynamic_object_size(array_annotated->c, 1), > + array_annotated->b * sizeof (int)); > + expect(__builtin_dynamic_object_size(array_nested_annotated->c, 1), > + array_nested_annotated->b * sizeof (int)); > +} > + > +int main(int argc, char *argv[]) > +{ > + setup (10,10); > + test (); > + DONE (); > +} > diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > new file mode 100644 > index 000000000000..a0c3cb88ec71 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > @@ -0,0 +1,210 @@ > +/* test the attribute counted_by and its usage in > +__builtin_dynamic_object_size: what's the correct behavior when the > +allocation size mismatched with the value of counted_by attribute? */ > +/* { dg-do run } */ > +/* { dg-options "-O -fstrict-flex-arrays=3" } */ > + > +#include "builtin-object-size-common.h" > + > +struct annotated { > + size_t foo; > + char others; > + char array[] __attribute__((counted_by (foo))); > +}; > + > +#define expect(p, _v) do { \ > + size_t v = _v; \ > + if (p == v) \ > + __builtin_printf ("ok: %s == %zd\n", #p, p); \ > + else \ > + { \ > + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ > + FAIL (); \ > + } \ > +} while (0); > + > +#define noinline __attribute__((__noinline__)) > +#define SIZE_BUMP 10 > +#define MAX(a, b) ((a) > (b) ? (a) : (b)) > +#define MIN(a, b) ((a) < (b) ? (a) : (b)) > + > +/* In general, Due to type casting, the type for the pointee of a pointer > + does not say anything about the object it points to, > + So, __builtin_object_size can not directly use the type of the pointee > + to decide the size of the object the pointer points to. > + > + there are only two reliable ways: > + A. observed allocations (call to the allocation functions in the routine) > + B. observed accesses (read or write access to the location of the > + pointer points to) > + > + that provide information about the type/existence of an object at > + the corresponding address. > + > + for A, we use the "alloc_size" attribute for the corresponding allocation > + functions to determine the object size; > + > + For B, we use the SIZE info of the TYPE attached to the corresponding access. > + (We treat counted_by attribute as a complement to the SIZE info of the TYPE > + for FMA) > + > + The only other way in C which ensures that a pointer actually points > + to an object of the correct type is 'static': > + > + void foo(struct P *p[static 1]); > + > + See https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624814.html > + for more details. */ > + > +/* in the following function, malloc allocated more space than the value > + of counted_by attribute. Then what's the correct behavior we expect > + the __builtin_dynamic_object_size should have for each of the cases? */ > + > +static struct annotated * noinline alloc_buf_more (size_t index) > +{ > + struct annotated *p; > + size_t allocated_size > + = MAX (sizeof (struct annotated), > + (__builtin_offsetof (struct annotated, array[0]) > + + (index + SIZE_BUMP) * sizeof (char))); > + p = (struct annotated *) malloc (allocated_size); > + > + p->foo = index; > + > + /*when checking the observed access p->array, we have info on both > + observered allocation and observed access, > + A. from observed allocation: > + allocated_size - offsetof (struct annotated, array[0]) > + B. from observed access: p->foo * sizeof (char) > + */ > + > + /* for size in the whole object: always uses A. */ > + /* for size in the sub-object: chose the smaller of A and B. > + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html > + * for details on why. */ > + > + /* for MAXIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 1), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /* for MINIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 2), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 3), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /*when checking the pointer p, we only have info on the observed allocation. > + So, the object size info can only been obtained from the call to malloc. > + for both MAXIMUM and MINIMUM: A = (index + SIZE_BUMP) * sizeof (char) */ > + expect(__builtin_dynamic_object_size(p, 0), allocated_size); > + expect(__builtin_dynamic_object_size(p, 1), allocated_size); > + expect(__builtin_dynamic_object_size(p, 2), allocated_size); > + expect(__builtin_dynamic_object_size(p, 3), allocated_size); > + return p; > +} > + > +/* in the following function, malloc allocated less space than the value > + of counted_by attribute. Then what's the correct behavior we expect > + the __builtin_dynamic_object_size should have for each of the cases? > + NOTE: this is an user error, GCC should issue warnings for such case. > + this is a seperate issue we should address later. */ > + > +static struct annotated * noinline alloc_buf_less (size_t index) > +{ > + struct annotated *p; > + size_t allocated_size > + = MAX (sizeof (struct annotated), > + (__builtin_offsetof (struct annotated, array[0]) > + + (index) * sizeof (char))); > + p = (struct annotated *) malloc (allocated_size); > + > + p->foo = index + SIZE_BUMP; > + > + /*when checking the observed access p->array, we have info on both > + observered allocation and observed access, > + A. from observed allocation: > + allocated_size - offsetof (struct annotated, array[0]) > + B. from observed access: p->foo * sizeof (char) > + */ > + > + /* for size in the whole object: always uses A. */ > + /* for size in the sub-object: chose the smaller of A and B. > + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html > + * for details on why. */ > + > + /* for MAXIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 1), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /* for MINIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 2), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 3), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /*when checking the pointer p, we only have info on the observed > + allocation. So, the object size info can only been obtained from > + the call to malloc. */ > + expect(__builtin_dynamic_object_size(p, 0), allocated_size); > + expect(__builtin_dynamic_object_size(p, 1), allocated_size); > + expect(__builtin_dynamic_object_size(p, 2), allocated_size); > + expect(__builtin_dynamic_object_size(p, 3), allocated_size); > + return p; > +} > + > +int main () > +{ > + struct annotated *p, *q; > + p = alloc_buf_more (10); > + q = alloc_buf_less (10); > + > + /*when checking the observed access p->array, we only have info on the > + observed access, i.e, the TYPE_SIZE info from the access. We don't have > + info on the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), -1); > + expect(__builtin_dynamic_object_size(p->array, 1), p->foo * sizeof(char)); > + expect(__builtin_dynamic_object_size(p->array, 2), 0); > + expect(__builtin_dynamic_object_size(p->array, 3), p->foo * sizeof(char)); > + /*when checking the pointer p, we have no observed allocation nor observed > + access, therefore, we cannot determine the size info here. */ > + expect(__builtin_dynamic_object_size(p, 0), -1); > + expect(__builtin_dynamic_object_size(p, 1), -1); > + expect(__builtin_dynamic_object_size(p, 2), 0); > + expect(__builtin_dynamic_object_size(p, 3), 0); > + > + /*when checking the observed access p->array, we only have info on the > + observed access, i.e, the TYPE_SIZE info from the access. We don't have > + info on the whole object. */ > + expect(__builtin_dynamic_object_size(q->array, 0), -1); > + expect(__builtin_dynamic_object_size(q->array, 1), q->foo * sizeof(char)); > + expect(__builtin_dynamic_object_size(q->array, 2), 0); > + expect(__builtin_dynamic_object_size(q->array, 3), q->foo * sizeof(char)); > + /*when checking the pointer p, we have no observed allocation nor observed > + access, therefore, we cannot determine the size info here. */ > + expect(__builtin_dynamic_object_size(q, 0), -1); > + expect(__builtin_dynamic_object_size(q, 1), -1); > + expect(__builtin_dynamic_object_size(q, 2), 0); > + expect(__builtin_dynamic_object_size(q, 3), 0); > + > + DONE (); > +} > diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc > index a62af0500563..cf7843c5684b 100644 > --- a/gcc/tree-object-size.cc > +++ b/gcc/tree-object-size.cc > @@ -585,6 +585,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > if (pt_var != TREE_OPERAND (ptr, 0)) > { > tree var; > + tree counted_by_ref = NULL_TREE; > > if (object_size_type & OST_SUBOBJECT) > { > @@ -600,11 +601,12 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > var = TREE_OPERAND (var, 0); > if (var != pt_var && TREE_CODE (var) == ARRAY_REF) > var = TREE_OPERAND (var, 0); > - if (! TYPE_SIZE_UNIT (TREE_TYPE (var)) > + if (! component_ref_has_counted_by_p (var) > + && ((! TYPE_SIZE_UNIT (TREE_TYPE (var)) > || ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var))) > || (pt_var_size && TREE_CODE (pt_var_size) == INTEGER_CST > && tree_int_cst_lt (pt_var_size, > - TYPE_SIZE_UNIT (TREE_TYPE (var))))) > + TYPE_SIZE_UNIT (TREE_TYPE (var))))))) > var = pt_var; > else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF) > { > @@ -612,6 +614,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > /* For &X->fld, compute object size if fld isn't a flexible array > member. */ > bool is_flexible_array_mem_ref = false; > + > while (v && v != pt_var) > switch (TREE_CODE (v)) > { > @@ -660,6 +663,8 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > /* Now the ref is to an array type. */ > gcc_assert (TREE_CODE (TREE_TYPE (v)) == ARRAY_TYPE); > is_flexible_array_mem_ref = array_ref_flexible_size_p (v); > + counted_by_ref = component_ref_get_counted_by (v); > + > while (v != pt_var && TREE_CODE (v) == COMPONENT_REF) > if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0))) > != UNION_TYPE > @@ -673,8 +678,11 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > == RECORD_TYPE) > { > /* compute object size only if v is not a > - flexible array member. */ > - if (!is_flexible_array_mem_ref) > + flexible array member or the flexible array member > + has a known element count indicated by the user > + through attribute counted_by. */ > + if (!is_flexible_array_mem_ref > + || counted_by_ref) > { > v = NULL_TREE; > break; > @@ -707,9 +715,24 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > > if (var != pt_var) > { > - var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); > - if (!TREE_CONSTANT (var_size)) > - var_size = get_or_create_ssa_default_def (cfun, var_size); > + if (!counted_by_ref) > + { > + var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); > + if (!TREE_CONSTANT (var_size)) > + var_size = get_or_create_ssa_default_def (cfun, var_size); > + } > + else > + { > + gcc_assert (TREE_CODE (var) == COMPONENT_REF > + && TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE); > + tree element_size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (var))); > + var_size > + = size_binop (MULT_EXPR, > + fold_convert (sizetype, counted_by_ref), > + fold_convert (sizetype, element_size)); > + if (!todo) > + todo = TODO_update_ssa_only_virtuals; > + } > if (!var_size) > return false; > } > diff --git a/gcc/tree.cc b/gcc/tree.cc > index fcd36ae0cd74..3b6ddcbdcbf8 100644 > --- a/gcc/tree.cc > +++ b/gcc/tree.cc > @@ -12745,6 +12745,32 @@ array_ref_element_size (tree exp) > return SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (elmt_type), exp); > } > > +/* For a component_ref that has an array type ARRAY_REF, return TRUE when > + an counted_by attribute attached to the corresponding FIELD_DECL. > + return FALSE otherwise. */ > +bool > +component_ref_has_counted_by_p (tree array_ref) > +{ > + if (TREE_CODE (array_ref) != COMPONENT_REF) > + return false; > + > + if (TREE_CODE (TREE_TYPE (array_ref)) != ARRAY_TYPE) > + return false; > + > + tree struct_object = TREE_OPERAND (array_ref, 0); > + tree struct_type = TREE_TYPE (struct_object); > + > + if (!RECORD_OR_UNION_TYPE_P (struct_type)) > + return false; > + tree field_decl = TREE_OPERAND (array_ref, 1); > + tree attr_counted_by = lookup_attribute ("counted_by", > + DECL_ATTRIBUTES (field_decl)); > + > + if (!attr_counted_by) > + return false; > + return true; > +} > + > /* Given a field list, FIELDLIST, of a structure/union, return a TREE_LIST, > with each TREE_VALUE a FIELD_DECL stepping down the chain to the FIELD > whose name is FIELDNAME, which is the last TREE_VALUE of the list. > @@ -12771,7 +12797,7 @@ get_named_field (tree fieldlist, const char *fieldname) > fields inside it recursively. */ > else if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (field))) > if ((named_field = get_named_field (TYPE_FIELDS (TREE_TYPE (field)), > - fieldname)) != NULL_TREE) > + fieldname)) != NULL_TREE) > { > named_field = tree_cons (NULL_TREE, field, named_field); > break; > @@ -12784,6 +12810,73 @@ get_named_field (tree fieldlist, const char *fieldname) > return named_field; > } > > +/* For a component_ref that has an array type ARRAY_REF, get the object that > + represents its counted_by per the attribute counted_by attached to > + the corresponding FIELD_DECL. return NULL_TREE when cannot find such > + object. > + For example, if: > + > + struct P { > + int k; > + int x[] __attribute__ ((counted_by (k))); > + } *p; > + > + for the following reference: > + > + p->x[b] > + > + the object that represents its element count will be: > + > + p->k > + > + So, when component_ref_get_counted_by (p->x[b]) is called, p->k should be > + returned. > +*/ > + > +tree > +component_ref_get_counted_by (tree array_ref) > +{ > + if (! component_ref_has_counted_by_p (array_ref)) > + return NULL_TREE; > + > + tree struct_object = TREE_OPERAND (array_ref, 0); > + tree struct_type = TREE_TYPE (struct_object); > + tree field_decl = TREE_OPERAND (array_ref, 1); > + tree attr_counted_by = lookup_attribute ("counted_by", > + DECL_ATTRIBUTES (field_decl)); > + gcc_assert (attr_counted_by); > + > + /* If there is an counted_by attribute attached to the field, > + get the field that maps to the counted_by. */ > + > + const char *fieldname > + = IDENTIFIER_POINTER (TREE_VALUE (TREE_VALUE (attr_counted_by))); > + > + tree counted_by_field = get_named_field (TYPE_FIELDS (struct_type), > + fieldname); > + > + gcc_assert (counted_by_field); > + > + /* generate the tree node that represent the counted_by of this array > + ref. This is a (possible nested) COMPONENT_REF to the counted_by_field > + of the containing structure. */ > + > + tree counted_by_ref = NULL_TREE; > + tree object = struct_object; > + do > + { > + tree field = TREE_VALUE (counted_by_field); > + > + counted_by_ref = build3 (COMPONENT_REF, > + TREE_TYPE (field), > + unshare_expr (object), field, > + NULL_TREE); > + object = counted_by_ref; > + counted_by_field = TREE_CHAIN (counted_by_field); > + } > + while (counted_by_field); > + return counted_by_ref; > +} > > /* Return a tree representing the lower bound of the array mentioned in > EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ > diff --git a/gcc/tree.h b/gcc/tree.h > index 4859becaa1e7..07eed7219835 100644 > --- a/gcc/tree.h > +++ b/gcc/tree.h > @@ -5619,11 +5619,21 @@ extern tree get_base_address (tree t); > of EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ > extern tree array_ref_element_size (tree); > > +/* Give a component_ref that has an array type, return true when an > + attribute counted_by attached to the corresponding FIELD_DECL. */ > +extern bool component_ref_has_counted_by_p (tree); > + > /* Given a field list, FIELDLIST, of a structure/union, return the FIELD whose > name is FIELDNAME, return NULL_TREE if such field is not found. > searching nested anonymous structure/union recursively. */ > extern tree get_named_field (tree, const char *); > > +/* Give a component_ref that has an array type, return the object that > + represents its counted_by per the attribute counted_by attached to > + the corresponding FIELD_DECL. return NULL_TREE when cannot find such > + object. */ > +extern tree component_ref_get_counted_by (tree); > + > /* Return a typenode for the "standard" C type with a given name. */ > extern tree get_typenode_from_name (const char *); > > -- > 2.31.1 >
On 2023-08-25 11:24, Qing Zhao wrote: > Use the counted_by atribute info in builtin object size to compute the > subobject size for flexible array members. > > gcc/ChangeLog: > > PR C/108896 > * tree-object-size.cc (addr_object_size): Use the counted_by > attribute info. > * tree.cc (component_ref_has_counted_by_p): New function. > (component_ref_get_counted_by): New function. > * tree.h (component_ref_has_counted_by_p): New prototype. > (component_ref_get_counted_by): New prototype. > > gcc/testsuite/ChangeLog: > > PR C/108896 > * gcc.dg/flex-array-counted-by-2.c: New test. > * gcc.dg/flex-array-counted-by-3.c: New test. > --- > .../gcc.dg/flex-array-counted-by-2.c | 74 ++++++ > .../gcc.dg/flex-array-counted-by-3.c | 210 ++++++++++++++++++ > gcc/tree-object-size.cc | 37 ++- > gcc/tree.cc | 95 +++++++- > gcc/tree.h | 10 + > 5 files changed, 418 insertions(+), 8 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > > diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > new file mode 100644 > index 000000000000..ec580c1f1f01 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c > @@ -0,0 +1,74 @@ > +/* test the attribute counted_by and its usage in > + * __builtin_dynamic_object_size. */ > +/* { dg-do run } */ > +/* { dg-options "-O2" } */ > + > +#include "builtin-object-size-common.h" > + > +#define expect(p, _v) do { \ > + size_t v = _v; \ > + if (p == v) \ > + __builtin_printf ("ok: %s == %zd\n", #p, p); \ > + else \ > + { \ > + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ > + FAIL (); \ > + } \ > +} while (0); You're using this in a bunch of tests already; does it make sense to consolidate it into builtin-object-size-common.h? > + > +struct flex { > + int b; > + int c[]; > +} *array_flex; > + > +struct annotated { > + int b; > + int c[] __attribute__ ((counted_by (b))); > +} *array_annotated; > + > +struct nested_annotated { > + struct { > + union { > + int b; > + float f; > + }; > + int n; > + }; > + int c[] __attribute__ ((counted_by (b))); > +} *array_nested_annotated; > + > +void __attribute__((__noinline__)) setup (int normal_count, int attr_count) > +{ > + array_flex > + = (struct flex *)malloc (sizeof (struct flex) > + + normal_count * sizeof (int)); > + array_flex->b = normal_count; > + > + array_annotated > + = (struct annotated *)malloc (sizeof (struct annotated) > + + attr_count * sizeof (int)); > + array_annotated->b = attr_count; > + > + array_nested_annotated > + = (struct nested_annotated *)malloc (sizeof (struct nested_annotated) > + + attr_count * sizeof (int)); > + array_nested_annotated->b = attr_count; > + > + return; > +} > + > +void __attribute__((__noinline__)) test () > +{ > + expect(__builtin_dynamic_object_size(array_flex->c, 1), -1); > + expect(__builtin_dynamic_object_size(array_annotated->c, 1), > + array_annotated->b * sizeof (int)); > + expect(__builtin_dynamic_object_size(array_nested_annotated->c, 1), > + array_nested_annotated->b * sizeof (int)); > +} Maybe another test where the allocation, size assignment and __bdos call happen in the same function, where the allocator is not recognized by gcc: void * __attribute__ ((noinline)) alloc (size_t sz) { return __builtin_malloc (sz); } void test (size_t sz) { array_annotated = alloc (sz); array_annotated->b = sz; return __builtin_dynamic_object_size (array_annotated->c, 1); } The interesting thing to test (and ensure in the codegen) is that the assignment to array_annotated->b does not get reordered to below the __builtin_dynamic_object_size call since technically there is no data dependency between the two. > + > +int main(int argc, char *argv[]) > +{ > + setup (10,10); > + test (); > + DONE (); > +} > diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > new file mode 100644 > index 000000000000..a0c3cb88ec71 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c > @@ -0,0 +1,210 @@ > +/* test the attribute counted_by and its usage in > +__builtin_dynamic_object_size: what's the correct behavior when the > +allocation size mismatched with the value of counted_by attribute? */ If the behaviour is undefined, does it make sense to add tests for this? Maybe once you have a -Wmismatched-counted-by or similar, we could have tests for that. I guess the counter-argument is that we keep track of this behaviour but not necessarily guarantee it. > +/* { dg-do run } */ > +/* { dg-options "-O -fstrict-flex-arrays=3" } */ > + > +#include "builtin-object-size-common.h" > + > +struct annotated { > + size_t foo; > + char others; > + char array[] __attribute__((counted_by (foo))); > +}; > + > +#define expect(p, _v) do { \ > + size_t v = _v; \ > + if (p == v) \ > + __builtin_printf ("ok: %s == %zd\n", #p, p); \ > + else \ > + { \ > + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ > + FAIL (); \ > + } \ > +} while (0); Same, maybe consolidate this into builtin-object-size-common.h. > + > +#define noinline __attribute__((__noinline__)) > +#define SIZE_BUMP 10 > +#define MAX(a, b) ((a) > (b) ? (a) : (b)) > +#define MIN(a, b) ((a) < (b) ? (a) : (b)) > + > +/* In general, Due to type casting, the type for the pointee of a pointer > + does not say anything about the object it points to, > + So, __builtin_object_size can not directly use the type of the pointee > + to decide the size of the object the pointer points to. > + > + there are only two reliable ways: > + A. observed allocations (call to the allocation functions in the routine) > + B. observed accesses (read or write access to the location of the > + pointer points to) > + > + that provide information about the type/existence of an object at > + the corresponding address. > + > + for A, we use the "alloc_size" attribute for the corresponding allocation > + functions to determine the object size; > + > + For B, we use the SIZE info of the TYPE attached to the corresponding access. > + (We treat counted_by attribute as a complement to the SIZE info of the TYPE > + for FMA) > + > + The only other way in C which ensures that a pointer actually points > + to an object of the correct type is 'static': > + > + void foo(struct P *p[static 1]); > + > + See https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624814.html > + for more details. */ > + > +/* in the following function, malloc allocated more space than the value > + of counted_by attribute. Then what's the correct behavior we expect > + the __builtin_dynamic_object_size should have for each of the cases? */ > + > +static struct annotated * noinline alloc_buf_more (size_t index) > +{ > + struct annotated *p; > + size_t allocated_size > + = MAX (sizeof (struct annotated), > + (__builtin_offsetof (struct annotated, array[0]) > + + (index + SIZE_BUMP) * sizeof (char))); > + p = (struct annotated *) malloc (allocated_size); > + > + p->foo = index; > + > + /*when checking the observed access p->array, we have info on both > + observered allocation and observed access, > + A. from observed allocation: > + allocated_size - offsetof (struct annotated, array[0]) > + B. from observed access: p->foo * sizeof (char) > + */ > + > + /* for size in the whole object: always uses A. */ > + /* for size in the sub-object: chose the smaller of A and B. > + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html > + * for details on why. */ > + > + /* for MAXIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 1), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /* for MINIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 2), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 3), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /*when checking the pointer p, we only have info on the observed allocation. > + So, the object size info can only been obtained from the call to malloc. > + for both MAXIMUM and MINIMUM: A = (index + SIZE_BUMP) * sizeof (char) */ > + expect(__builtin_dynamic_object_size(p, 0), allocated_size); > + expect(__builtin_dynamic_object_size(p, 1), allocated_size); > + expect(__builtin_dynamic_object_size(p, 2), allocated_size); > + expect(__builtin_dynamic_object_size(p, 3), allocated_size); > + return p; > +} > + > +/* in the following function, malloc allocated less space than the value > + of counted_by attribute. Then what's the correct behavior we expect > + the __builtin_dynamic_object_size should have for each of the cases? > + NOTE: this is an user error, GCC should issue warnings for such case. > + this is a seperate issue we should address later. */ > + > +static struct annotated * noinline alloc_buf_less (size_t index) > +{ > + struct annotated *p; > + size_t allocated_size > + = MAX (sizeof (struct annotated), > + (__builtin_offsetof (struct annotated, array[0]) > + + (index) * sizeof (char))); > + p = (struct annotated *) malloc (allocated_size); > + > + p->foo = index + SIZE_BUMP; > + > + /*when checking the observed access p->array, we have info on both > + observered allocation and observed access, > + A. from observed allocation: > + allocated_size - offsetof (struct annotated, array[0]) > + B. from observed access: p->foo * sizeof (char) > + */ > + > + /* for size in the whole object: always uses A. */ > + /* for size in the sub-object: chose the smaller of A and B. > + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html > + * for details on why. */ > + > + /* for MAXIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 1), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /* for MINIMUM size in the whole object: use the allocation size > + for the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 2), > + allocated_size - __builtin_offsetof (struct annotated, array[0])); > + > + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ > + expect(__builtin_dynamic_object_size(p->array, 3), > + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), > + (p->foo) * sizeof(char))); > + > + /*when checking the pointer p, we only have info on the observed > + allocation. So, the object size info can only been obtained from > + the call to malloc. */ > + expect(__builtin_dynamic_object_size(p, 0), allocated_size); > + expect(__builtin_dynamic_object_size(p, 1), allocated_size); > + expect(__builtin_dynamic_object_size(p, 2), allocated_size); > + expect(__builtin_dynamic_object_size(p, 3), allocated_size); > + return p; > +} > + > +int main () > +{ > + struct annotated *p, *q; > + p = alloc_buf_more (10); > + q = alloc_buf_less (10); > + > + /*when checking the observed access p->array, we only have info on the > + observed access, i.e, the TYPE_SIZE info from the access. We don't have > + info on the whole object. */ > + expect(__builtin_dynamic_object_size(p->array, 0), -1); > + expect(__builtin_dynamic_object_size(p->array, 1), p->foo * sizeof(char)); > + expect(__builtin_dynamic_object_size(p->array, 2), 0); > + expect(__builtin_dynamic_object_size(p->array, 3), p->foo * sizeof(char)); > + /*when checking the pointer p, we have no observed allocation nor observed > + access, therefore, we cannot determine the size info here. */ > + expect(__builtin_dynamic_object_size(p, 0), -1); > + expect(__builtin_dynamic_object_size(p, 1), -1); > + expect(__builtin_dynamic_object_size(p, 2), 0); > + expect(__builtin_dynamic_object_size(p, 3), 0); > + > + /*when checking the observed access p->array, we only have info on the > + observed access, i.e, the TYPE_SIZE info from the access. We don't have > + info on the whole object. */ > + expect(__builtin_dynamic_object_size(q->array, 0), -1); > + expect(__builtin_dynamic_object_size(q->array, 1), q->foo * sizeof(char)); > + expect(__builtin_dynamic_object_size(q->array, 2), 0); > + expect(__builtin_dynamic_object_size(q->array, 3), q->foo * sizeof(char)); > + /*when checking the pointer p, we have no observed allocation nor observed > + access, therefore, we cannot determine the size info here. */ > + expect(__builtin_dynamic_object_size(q, 0), -1); > + expect(__builtin_dynamic_object_size(q, 1), -1); > + expect(__builtin_dynamic_object_size(q, 2), 0); > + expect(__builtin_dynamic_object_size(q, 3), 0); > + > + DONE (); > +} > diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc > index a62af0500563..cf7843c5684b 100644 > --- a/gcc/tree-object-size.cc > +++ b/gcc/tree-object-size.cc > @@ -585,6 +585,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > if (pt_var != TREE_OPERAND (ptr, 0)) > { > tree var; > + tree counted_by_ref = NULL_TREE; > > if (object_size_type & OST_SUBOBJECT) > { > @@ -600,11 +601,12 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > var = TREE_OPERAND (var, 0); > if (var != pt_var && TREE_CODE (var) == ARRAY_REF) > var = TREE_OPERAND (var, 0); > - if (! TYPE_SIZE_UNIT (TREE_TYPE (var)) > + if (! component_ref_has_counted_by_p (var) > + && ((! TYPE_SIZE_UNIT (TREE_TYPE (var)) > || ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var))) > || (pt_var_size && TREE_CODE (pt_var_size) == INTEGER_CST > && tree_int_cst_lt (pt_var_size, > - TYPE_SIZE_UNIT (TREE_TYPE (var))))) > + TYPE_SIZE_UNIT (TREE_TYPE (var))))))) > var = pt_var; > else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF) > { Hmm, only for subobject size? I thought we had consensus on using sizeof (struct) + counted_by_size as the conservative maximum size for whole object size too, didn't we? > @@ -612,6 +614,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > /* For &X->fld, compute object size if fld isn't a flexible array > member. */ > bool is_flexible_array_mem_ref = false; > + > while (v && v != pt_var) > switch (TREE_CODE (v)) > { Unnecessary newline. > @@ -660,6 +663,8 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > /* Now the ref is to an array type. */ > gcc_assert (TREE_CODE (TREE_TYPE (v)) == ARRAY_TYPE); > is_flexible_array_mem_ref = array_ref_flexible_size_p (v); > + counted_by_ref = component_ref_get_counted_by (v); > + > while (v != pt_var && TREE_CODE (v) == COMPONENT_REF) > if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0))) > != UNION_TYPE > @@ -673,8 +678,11 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > == RECORD_TYPE) > { > /* compute object size only if v is not a > - flexible array member. */ > - if (!is_flexible_array_mem_ref) > + flexible array member or the flexible array member > + has a known element count indicated by the user > + through attribute counted_by. */ > + if (!is_flexible_array_mem_ref > + || counted_by_ref) > { > v = NULL_TREE; > break; > @@ -707,9 +715,24 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, > > if (var != pt_var) > { > - var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); > - if (!TREE_CONSTANT (var_size)) > - var_size = get_or_create_ssa_default_def (cfun, var_size); > + if (!counted_by_ref) > + { > + var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); > + if (!TREE_CONSTANT (var_size)) > + var_size = get_or_create_ssa_default_def (cfun, var_size); > + } > + else > + { > + gcc_assert (TREE_CODE (var) == COMPONENT_REF > + && TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE); > + tree element_size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (var))); > + var_size > + = size_binop (MULT_EXPR, > + fold_convert (sizetype, counted_by_ref), > + fold_convert (sizetype, element_size)); > + if (!todo) > + todo = TODO_update_ssa_only_virtuals; > + } I feel like this could make a good separate function (get_subobject_size or something like that) to make it easier to read. > if (!var_size) > return false; > } > diff --git a/gcc/tree.cc b/gcc/tree.cc > index fcd36ae0cd74..3b6ddcbdcbf8 100644 > --- a/gcc/tree.cc > +++ b/gcc/tree.cc > @@ -12745,6 +12745,32 @@ array_ref_element_size (tree exp) > return SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (elmt_type), exp); > } > > +/* For a component_ref that has an array type ARRAY_REF, return TRUE when > + an counted_by attribute attached to the corresponding FIELD_DECL. > + return FALSE otherwise. */ > +bool > +component_ref_has_counted_by_p (tree array_ref) > +{ > + if (TREE_CODE (array_ref) != COMPONENT_REF) > + return false; > + > + if (TREE_CODE (TREE_TYPE (array_ref)) != ARRAY_TYPE) > + return false; > + > + tree struct_object = TREE_OPERAND (array_ref, 0); > + tree struct_type = TREE_TYPE (struct_object); > + > + if (!RECORD_OR_UNION_TYPE_P (struct_type)) > + return false; > + tree field_decl = TREE_OPERAND (array_ref, 1); > + tree attr_counted_by = lookup_attribute ("counted_by", > + DECL_ATTRIBUTES (field_decl)); > + > + if (!attr_counted_by) > + return false; > + return true; > +} > + > /* Given a field list, FIELDLIST, of a structure/union, return a TREE_LIST, > with each TREE_VALUE a FIELD_DECL stepping down the chain to the FIELD > whose name is FIELDNAME, which is the last TREE_VALUE of the list. > @@ -12771,7 +12797,7 @@ get_named_field (tree fieldlist, const char *fieldname) > fields inside it recursively. */ > else if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (field))) > if ((named_field = get_named_field (TYPE_FIELDS (TREE_TYPE (field)), > - fieldname)) != NULL_TREE) > + fieldname)) != NULL_TREE) Unrelated whitespace change? > { > named_field = tree_cons (NULL_TREE, field, named_field); > break; > @@ -12784,6 +12810,73 @@ get_named_field (tree fieldlist, const char *fieldname) > return named_field; > } > > +/* For a component_ref that has an array type ARRAY_REF, get the object that > + represents its counted_by per the attribute counted_by attached to > + the corresponding FIELD_DECL. return NULL_TREE when cannot find such > + object. > + For example, if: > + > + struct P { > + int k; > + int x[] __attribute__ ((counted_by (k))); > + } *p; > + > + for the following reference: > + > + p->x[b] > + > + the object that represents its element count will be: > + > + p->k > + > + So, when component_ref_get_counted_by (p->x[b]) is called, p->k should be > + returned. > +*/ > + > +tree > +component_ref_get_counted_by (tree array_ref) > +{ > + if (! component_ref_has_counted_by_p (array_ref)) > + return NULL_TREE; > + > + tree struct_object = TREE_OPERAND (array_ref, 0); > + tree struct_type = TREE_TYPE (struct_object); > + tree field_decl = TREE_OPERAND (array_ref, 1); > + tree attr_counted_by = lookup_attribute ("counted_by", > + DECL_ATTRIBUTES (field_decl)); > + gcc_assert (attr_counted_by); > + > + /* If there is an counted_by attribute attached to the field, > + get the field that maps to the counted_by. */ > + > + const char *fieldname > + = IDENTIFIER_POINTER (TREE_VALUE (TREE_VALUE (attr_counted_by))); > + > + tree counted_by_field = get_named_field (TYPE_FIELDS (struct_type), > + fieldname); > + > + gcc_assert (counted_by_field); > + > + /* generate the tree node that represent the counted_by of this array Capitalize first word. Also s/represent/represents/ > + ref. This is a (possible nested) COMPONENT_REF to the counted_by_field possibly nested > + of the containing structure. */ > + > + tree counted_by_ref = NULL_TREE; > + tree object = struct_object; > + do > + { > + tree field = TREE_VALUE (counted_by_field); > + > + counted_by_ref = build3 (COMPONENT_REF, > + TREE_TYPE (field), > + unshare_expr (object), field, > + NULL_TREE); > + object = counted_by_ref; > + counted_by_field = TREE_CHAIN (counted_by_field); > + } > + while (counted_by_field); > + return counted_by_ref; > +} > > /* Return a tree representing the lower bound of the array mentioned in > EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ > diff --git a/gcc/tree.h b/gcc/tree.h > index 4859becaa1e7..07eed7219835 100644 > --- a/gcc/tree.h > +++ b/gcc/tree.h > @@ -5619,11 +5619,21 @@ extern tree get_base_address (tree t); > of EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ > extern tree array_ref_element_size (tree); > > +/* Give a component_ref that has an array type, return true when an > + attribute counted_by attached to the corresponding FIELD_DECL. */ > +extern bool component_ref_has_counted_by_p (tree); > + > /* Given a field list, FIELDLIST, of a structure/union, return the FIELD whose > name is FIELDNAME, return NULL_TREE if such field is not found. > searching nested anonymous structure/union recursively. */ > extern tree get_named_field (tree, const char *); > > +/* Give a component_ref that has an array type, return the object that > + represents its counted_by per the attribute counted_by attached to > + the corresponding FIELD_DECL. return NULL_TREE when cannot find such > + object. */ > +extern tree component_ref_get_counted_by (tree); > + > /* Return a typenode for the "standard" C type with a given name. */ > extern tree get_typenode_from_name (const char *); >
Hi, Sid, Thanks a lot for the detailed comments. See my responds embedded below. Qing > On Oct 5, 2023, at 4:01 PM, Siddhesh Poyarekar <siddhesh@gotplt.org> wrote: > > > > On 2023-08-25 11:24, Qing Zhao wrote: >> Use the counted_by atribute info in builtin object size to compute the >> subobject size for flexible array members. >> gcc/ChangeLog: >> PR C/108896 >> * tree-object-size.cc (addr_object_size): Use the counted_by >> attribute info. >> * tree.cc (component_ref_has_counted_by_p): New function. >> (component_ref_get_counted_by): New function. >> * tree.h (component_ref_has_counted_by_p): New prototype. >> (component_ref_get_counted_by): New prototype. >> gcc/testsuite/ChangeLog: >> PR C/108896 >> * gcc.dg/flex-array-counted-by-2.c: New test. >> * gcc.dg/flex-array-counted-by-3.c: New test. >> --- >> .../gcc.dg/flex-array-counted-by-2.c | 74 ++++++ >> .../gcc.dg/flex-array-counted-by-3.c | 210 ++++++++++++++++++ >> gcc/tree-object-size.cc | 37 ++- >> gcc/tree.cc | 95 +++++++- >> gcc/tree.h | 10 + >> 5 files changed, 418 insertions(+), 8 deletions(-) >> create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-2.c >> create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-3.c >> diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c >> new file mode 100644 >> index 000000000000..ec580c1f1f01 >> --- /dev/null >> +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c >> @@ -0,0 +1,74 @@ >> +/* test the attribute counted_by and its usage in >> + * __builtin_dynamic_object_size. */ >> +/* { dg-do run } */ >> +/* { dg-options "-O2" } */ >> + >> +#include "builtin-object-size-common.h" >> + >> +#define expect(p, _v) do { \ >> + size_t v = _v; \ >> + if (p == v) \ >> + __builtin_printf ("ok: %s == %zd\n", #p, p); \ >> + else \ >> + { \ >> + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ >> + FAIL (); \ >> + } \ >> +} while (0); > > You're using this in a bunch of tests already; does it make sense to consolidate it into builtin-object-size-common.h? Will do this. > >> + >> +struct flex { >> + int b; >> + int c[]; >> +} *array_flex; >> + >> +struct annotated { >> + int b; >> + int c[] __attribute__ ((counted_by (b))); >> +} *array_annotated; >> + >> +struct nested_annotated { >> + struct { >> + union { >> + int b; >> + float f; >> + }; >> + int n; >> + }; >> + int c[] __attribute__ ((counted_by (b))); >> +} *array_nested_annotated; >> + >> +void __attribute__((__noinline__)) setup (int normal_count, int attr_count) >> +{ >> + array_flex >> + = (struct flex *)malloc (sizeof (struct flex) >> + + normal_count * sizeof (int)); >> + array_flex->b = normal_count; >> + >> + array_annotated >> + = (struct annotated *)malloc (sizeof (struct annotated) >> + + attr_count * sizeof (int)); >> + array_annotated->b = attr_count; >> + >> + array_nested_annotated >> + = (struct nested_annotated *)malloc (sizeof (struct nested_annotated) >> + + attr_count * sizeof (int)); >> + array_nested_annotated->b = attr_count; >> + >> + return; >> +} >> + >> +void __attribute__((__noinline__)) test () >> +{ >> + expect(__builtin_dynamic_object_size(array_flex->c, 1), -1); >> + expect(__builtin_dynamic_object_size(array_annotated->c, 1), >> + array_annotated->b * sizeof (int)); >> + expect(__builtin_dynamic_object_size(array_nested_annotated->c, 1), >> + array_nested_annotated->b * sizeof (int)); >> +} > > Maybe another test where the allocation, size assignment and __bdos call happen in the same function, where the allocator is not recognized by gcc: > > void * > __attribute__ ((noinline)) > alloc (size_t sz) > { > return __builtin_malloc (sz); > } > > void test (size_t sz) > { > array_annotated = alloc (sz); > array_annotated->b = sz; > return __builtin_dynamic_object_size (array_annotated->c, 1); > } > > The interesting thing to test (and ensure in the codegen) is that the assignment to array_annotated->b does not get reordered to below the __builtin_dynamic_object_size call since technically there is no data dependency between the two. Good point. Will add such testing case. > >> + >> +int main(int argc, char *argv[]) >> +{ >> + setup (10,10); >> + test (); >> + DONE (); >> +} >> diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c >> new file mode 100644 >> index 000000000000..a0c3cb88ec71 >> --- /dev/null >> +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c >> @@ -0,0 +1,210 @@ >> +/* test the attribute counted_by and its usage in >> +__builtin_dynamic_object_size: what's the correct behavior when the >> +allocation size mismatched with the value of counted_by attribute? */ > > If the behaviour is undefined, does it make sense to add tests for this? Maybe once you have a -Wmismatched-counted-by or similar, we could have tests for that. I guess the counter-argument is that we keep track of this behaviour but not necessarily guarantee it. This testing case was added mainly for documentation purpose. It includes a detailed explanation on how the current _bdo estimates the size of the object. Even though there is mismatch between the actual allocation size and the value of counted_by attribute, the behavior of the compiler is still defined based on the algorithm. When -Wmismatched-counted-by is added later, we can update this testing case with new warning messages, but the behavior of _bdo still keep the same. > >> +/* { dg-do run } */ >> +/* { dg-options "-O -fstrict-flex-arrays=3" } */ >> + >> +#include "builtin-object-size-common.h" >> + >> +struct annotated { >> + size_t foo; >> + char others; >> + char array[] __attribute__((counted_by (foo))); >> +}; >> + >> +#define expect(p, _v) do { \ >> + size_t v = _v; \ >> + if (p == v) \ >> + __builtin_printf ("ok: %s == %zd\n", #p, p); \ >> + else \ >> + { \ >> + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ >> + FAIL (); \ >> + } \ >> +} while (0); > > Same, maybe consolidate this into builtin-object-size-common.h. Okay. > >> + >> +#define noinline __attribute__((__noinline__)) >> +#define SIZE_BUMP 10 >> +#define MAX(a, b) ((a) > (b) ? (a) : (b)) >> +#define MIN(a, b) ((a) < (b) ? (a) : (b)) >> + >> +/* In general, Due to type casting, the type for the pointee of a pointer >> + does not say anything about the object it points to, >> + So, __builtin_object_size can not directly use the type of the pointee >> + to decide the size of the object the pointer points to. >> + >> + there are only two reliable ways: >> + A. observed allocations (call to the allocation functions in the routine) >> + B. observed accesses (read or write access to the location of the >> + pointer points to) >> + >> + that provide information about the type/existence of an object at >> + the corresponding address. >> + >> + for A, we use the "alloc_size" attribute for the corresponding allocation >> + functions to determine the object size; >> + >> + For B, we use the SIZE info of the TYPE attached to the corresponding access. >> + (We treat counted_by attribute as a complement to the SIZE info of the TYPE >> + for FMA) >> + >> + The only other way in C which ensures that a pointer actually points >> + to an object of the correct type is 'static': >> + >> + void foo(struct P *p[static 1]); >> + >> + See https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624814.html >> + for more details. */ >> + >> +/* in the following function, malloc allocated more space than the value >> + of counted_by attribute. Then what's the correct behavior we expect >> + the __builtin_dynamic_object_size should have for each of the cases? */ >> + >> +static struct annotated * noinline alloc_buf_more (size_t index) >> +{ >> + struct annotated *p; >> + size_t allocated_size >> + = MAX (sizeof (struct annotated), >> + (__builtin_offsetof (struct annotated, array[0]) >> + + (index + SIZE_BUMP) * sizeof (char))); >> + p = (struct annotated *) malloc (allocated_size); >> + >> + p->foo = index; >> + >> + /*when checking the observed access p->array, we have info on both >> + observered allocation and observed access, >> + A. from observed allocation: >> + allocated_size - offsetof (struct annotated, array[0]) >> + B. from observed access: p->foo * sizeof (char) >> + */ >> + >> + /* for size in the whole object: always uses A. */ >> + /* for size in the sub-object: chose the smaller of A and B. >> + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html >> + * for details on why. */ >> + >> + /* for MAXIMUM size in the whole object: use the allocation size >> + for the whole object. */ >> + expect(__builtin_dynamic_object_size(p->array, 0), >> + allocated_size - __builtin_offsetof (struct annotated, array[0])); >> + >> + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ >> + expect(__builtin_dynamic_object_size(p->array, 1), >> + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), >> + (p->foo) * sizeof(char))); >> + >> + /* for MINIMUM size in the whole object: use the allocation size >> + for the whole object. */ >> + expect(__builtin_dynamic_object_size(p->array, 2), >> + allocated_size - __builtin_offsetof (struct annotated, array[0])); >> + >> + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ >> + expect(__builtin_dynamic_object_size(p->array, 3), >> + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), >> + (p->foo) * sizeof(char))); >> + >> + /*when checking the pointer p, we only have info on the observed allocation. >> + So, the object size info can only been obtained from the call to malloc. >> + for both MAXIMUM and MINIMUM: A = (index + SIZE_BUMP) * sizeof (char) */ >> + expect(__builtin_dynamic_object_size(p, 0), allocated_size); >> + expect(__builtin_dynamic_object_size(p, 1), allocated_size); >> + expect(__builtin_dynamic_object_size(p, 2), allocated_size); >> + expect(__builtin_dynamic_object_size(p, 3), allocated_size); >> + return p; >> +} >> + >> +/* in the following function, malloc allocated less space than the value >> + of counted_by attribute. Then what's the correct behavior we expect >> + the __builtin_dynamic_object_size should have for each of the cases? >> + NOTE: this is an user error, GCC should issue warnings for such case. >> + this is a seperate issue we should address later. */ >> + >> +static struct annotated * noinline alloc_buf_less (size_t index) >> +{ >> + struct annotated *p; >> + size_t allocated_size >> + = MAX (sizeof (struct annotated), >> + (__builtin_offsetof (struct annotated, array[0]) >> + + (index) * sizeof (char))); >> + p = (struct annotated *) malloc (allocated_size); >> + >> + p->foo = index + SIZE_BUMP; >> + >> + /*when checking the observed access p->array, we have info on both >> + observered allocation and observed access, >> + A. from observed allocation: >> + allocated_size - offsetof (struct annotated, array[0]) >> + B. from observed access: p->foo * sizeof (char) >> + */ >> + >> + /* for size in the whole object: always uses A. */ >> + /* for size in the sub-object: chose the smaller of A and B. >> + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html >> + * for details on why. */ >> + >> + /* for MAXIMUM size in the whole object: use the allocation size >> + for the whole object. */ >> + expect(__builtin_dynamic_object_size(p->array, 0), >> + allocated_size - __builtin_offsetof (struct annotated, array[0])); >> + >> + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ >> + expect(__builtin_dynamic_object_size(p->array, 1), >> + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), >> + (p->foo) * sizeof(char))); >> + >> + /* for MINIMUM size in the whole object: use the allocation size >> + for the whole object. */ >> + expect(__builtin_dynamic_object_size(p->array, 2), >> + allocated_size - __builtin_offsetof (struct annotated, array[0])); >> + >> + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ >> + expect(__builtin_dynamic_object_size(p->array, 3), >> + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), >> + (p->foo) * sizeof(char))); >> + >> + /*when checking the pointer p, we only have info on the observed >> + allocation. So, the object size info can only been obtained from >> + the call to malloc. */ >> + expect(__builtin_dynamic_object_size(p, 0), allocated_size); >> + expect(__builtin_dynamic_object_size(p, 1), allocated_size); >> + expect(__builtin_dynamic_object_size(p, 2), allocated_size); >> + expect(__builtin_dynamic_object_size(p, 3), allocated_size); >> + return p; >> +} >> + >> +int main () >> +{ >> + struct annotated *p, *q; >> + p = alloc_buf_more (10); >> + q = alloc_buf_less (10); >> + >> + /*when checking the observed access p->array, we only have info on the >> + observed access, i.e, the TYPE_SIZE info from the access. We don't have >> + info on the whole object. */ >> + expect(__builtin_dynamic_object_size(p->array, 0), -1); >> + expect(__builtin_dynamic_object_size(p->array, 1), p->foo * sizeof(char)); >> + expect(__builtin_dynamic_object_size(p->array, 2), 0); >> + expect(__builtin_dynamic_object_size(p->array, 3), p->foo * sizeof(char)); >> + /*when checking the pointer p, we have no observed allocation nor observed >> + access, therefore, we cannot determine the size info here. */ >> + expect(__builtin_dynamic_object_size(p, 0), -1); >> + expect(__builtin_dynamic_object_size(p, 1), -1); >> + expect(__builtin_dynamic_object_size(p, 2), 0); >> + expect(__builtin_dynamic_object_size(p, 3), 0); >> + >> + /*when checking the observed access p->array, we only have info on the >> + observed access, i.e, the TYPE_SIZE info from the access. We don't have >> + info on the whole object. */ >> + expect(__builtin_dynamic_object_size(q->array, 0), -1); >> + expect(__builtin_dynamic_object_size(q->array, 1), q->foo * sizeof(char)); >> + expect(__builtin_dynamic_object_size(q->array, 2), 0); >> + expect(__builtin_dynamic_object_size(q->array, 3), q->foo * sizeof(char)); >> + /*when checking the pointer p, we have no observed allocation nor observed >> + access, therefore, we cannot determine the size info here. */ >> + expect(__builtin_dynamic_object_size(q, 0), -1); >> + expect(__builtin_dynamic_object_size(q, 1), -1); >> + expect(__builtin_dynamic_object_size(q, 2), 0); >> + expect(__builtin_dynamic_object_size(q, 3), 0); >> + >> + DONE (); >> +} >> diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc >> index a62af0500563..cf7843c5684b 100644 >> --- a/gcc/tree-object-size.cc >> +++ b/gcc/tree-object-size.cc >> @@ -585,6 +585,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, >> if (pt_var != TREE_OPERAND (ptr, 0)) >> { >> tree var; >> + tree counted_by_ref = NULL_TREE; >> if (object_size_type & OST_SUBOBJECT) >> { >> @@ -600,11 +601,12 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, >> var = TREE_OPERAND (var, 0); >> if (var != pt_var && TREE_CODE (var) == ARRAY_REF) >> var = TREE_OPERAND (var, 0); >> - if (! TYPE_SIZE_UNIT (TREE_TYPE (var)) >> + if (! component_ref_has_counted_by_p (var) >> + && ((! TYPE_SIZE_UNIT (TREE_TYPE (var)) >> || ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var))) >> || (pt_var_size && TREE_CODE (pt_var_size) == INTEGER_CST >> && tree_int_cst_lt (pt_var_size, >> - TYPE_SIZE_UNIT (TREE_TYPE (var))))) >> + TYPE_SIZE_UNIT (TREE_TYPE (var))))))) >> var = pt_var; >> else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF) >> { > > Hmm, only for subobject size? I thought we had consensus on using sizeof (struct) + counted_by_size as the conservative maximum size for whole object size too, didn't we? Yes, in this initial patch set, only minimum change to tree-object-size.cc. therefore only handle subobject size. (And subobject size is more important for linux kernel security purpose) And I will add a follow up patch to add new code into tree-object-size.cc to support whole object size by using sizeof(struct) + counted_by_size. Is this Okay? > >> @@ -612,6 +614,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, >> /* For &X->fld, compute object size if fld isn't a flexible array >> member. */ >> bool is_flexible_array_mem_ref = false; >> + >> while (v && v != pt_var) >> switch (TREE_CODE (v)) >> { > > Unnecessary newline. Okay. > >> @@ -660,6 +663,8 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, >> /* Now the ref is to an array type. */ >> gcc_assert (TREE_CODE (TREE_TYPE (v)) == ARRAY_TYPE); >> is_flexible_array_mem_ref = array_ref_flexible_size_p (v); >> + counted_by_ref = component_ref_get_counted_by (v); >> + >> while (v != pt_var && TREE_CODE (v) == COMPONENT_REF) >> if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0))) >> != UNION_TYPE >> @@ -673,8 +678,11 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, >> == RECORD_TYPE) >> { >> /* compute object size only if v is not a >> - flexible array member. */ >> - if (!is_flexible_array_mem_ref) >> + flexible array member or the flexible array member >> + has a known element count indicated by the user >> + through attribute counted_by. */ >> + if (!is_flexible_array_mem_ref >> + || counted_by_ref) >> { >> v = NULL_TREE; >> break; >> @@ -707,9 +715,24 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, >> if (var != pt_var) >> { >> - var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); >> - if (!TREE_CONSTANT (var_size)) >> - var_size = get_or_create_ssa_default_def (cfun, var_size); >> + if (!counted_by_ref) >> + { >> + var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); >> + if (!TREE_CONSTANT (var_size)) >> + var_size = get_or_create_ssa_default_def (cfun, var_size); >> + } >> + else >> + { >> + gcc_assert (TREE_CODE (var) == COMPONENT_REF >> + && TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE); >> + tree element_size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (var))); >> + var_size >> + = size_binop (MULT_EXPR, >> + fold_convert (sizetype, counted_by_ref), >> + fold_convert (sizetype, element_size)); >> + if (!todo) >> + todo = TODO_update_ssa_only_virtuals; >> + } > > I feel like this could make a good separate function (get_subobject_size or something like that) to make it easier to read. Will try this in the next version. > >> if (!var_size) >> return false; >> } >> diff --git a/gcc/tree.cc b/gcc/tree.cc >> index fcd36ae0cd74..3b6ddcbdcbf8 100644 >> --- a/gcc/tree.cc >> +++ b/gcc/tree.cc >> @@ -12745,6 +12745,32 @@ array_ref_element_size (tree exp) >> return SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (elmt_type), exp); >> } >> +/* For a component_ref that has an array type ARRAY_REF, return TRUE when >> + an counted_by attribute attached to the corresponding FIELD_DECL. >> + return FALSE otherwise. */ >> +bool >> +component_ref_has_counted_by_p (tree array_ref) >> +{ >> + if (TREE_CODE (array_ref) != COMPONENT_REF) >> + return false; >> + >> + if (TREE_CODE (TREE_TYPE (array_ref)) != ARRAY_TYPE) >> + return false; >> + >> + tree struct_object = TREE_OPERAND (array_ref, 0); >> + tree struct_type = TREE_TYPE (struct_object); >> + >> + if (!RECORD_OR_UNION_TYPE_P (struct_type)) >> + return false; >> + tree field_decl = TREE_OPERAND (array_ref, 1); >> + tree attr_counted_by = lookup_attribute ("counted_by", >> + DECL_ATTRIBUTES (field_decl)); >> + >> + if (!attr_counted_by) >> + return false; >> + return true; >> +} >> + >> /* Given a field list, FIELDLIST, of a structure/union, return a TREE_LIST, >> with each TREE_VALUE a FIELD_DECL stepping down the chain to the FIELD >> whose name is FIELDNAME, which is the last TREE_VALUE of the list. >> @@ -12771,7 +12797,7 @@ get_named_field (tree fieldlist, const char *fieldname) >> fields inside it recursively. */ >> else if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (field))) >> if ((named_field = get_named_field (TYPE_FIELDS (TREE_TYPE (field)), >> - fieldname)) != NULL_TREE) >> + fieldname)) != NULL_TREE) > > Unrelated whitespace change? Will check on this and fix it in the next version. > >> { >> named_field = tree_cons (NULL_TREE, field, named_field); >> break; >> @@ -12784,6 +12810,73 @@ get_named_field (tree fieldlist, const char *fieldname) >> return named_field; >> } >> +/* For a component_ref that has an array type ARRAY_REF, get the object that >> + represents its counted_by per the attribute counted_by attached to >> + the corresponding FIELD_DECL. return NULL_TREE when cannot find such >> + object. >> + For example, if: >> + >> + struct P { >> + int k; >> + int x[] __attribute__ ((counted_by (k))); >> + } *p; >> + >> + for the following reference: >> + >> + p->x[b] >> + >> + the object that represents its element count will be: >> + >> + p->k >> + >> + So, when component_ref_get_counted_by (p->x[b]) is called, p->k should be >> + returned. >> +*/ >> + >> +tree >> +component_ref_get_counted_by (tree array_ref) >> +{ >> + if (! component_ref_has_counted_by_p (array_ref)) >> + return NULL_TREE; >> + >> + tree struct_object = TREE_OPERAND (array_ref, 0); >> + tree struct_type = TREE_TYPE (struct_object); >> + tree field_decl = TREE_OPERAND (array_ref, 1); >> + tree attr_counted_by = lookup_attribute ("counted_by", >> + DECL_ATTRIBUTES (field_decl)); >> + gcc_assert (attr_counted_by); >> + >> + /* If there is an counted_by attribute attached to the field, >> + get the field that maps to the counted_by. */ >> + >> + const char *fieldname >> + = IDENTIFIER_POINTER (TREE_VALUE (TREE_VALUE (attr_counted_by))); >> + >> + tree counted_by_field = get_named_field (TYPE_FIELDS (struct_type), >> + fieldname); >> + >> + gcc_assert (counted_by_field); >> + >> + /* generate the tree node that represent the counted_by of this array > > Capitalize first word. Also s/represent/represents/ Okay. > >> + ref. This is a (possible nested) COMPONENT_REF to the counted_by_field > > possibly nested Okay. > >> + of the containing structure. */ >> + >> + tree counted_by_ref = NULL_TREE; >> + tree object = struct_object; >> + do >> + { >> + tree field = TREE_VALUE (counted_by_field); >> + >> + counted_by_ref = build3 (COMPONENT_REF, >> + TREE_TYPE (field), >> + unshare_expr (object), field, >> + NULL_TREE); >> + object = counted_by_ref; >> + counted_by_field = TREE_CHAIN (counted_by_field); >> + } >> + while (counted_by_field); >> + return counted_by_ref; >> +} >> /* Return a tree representing the lower bound of the array mentioned in >> EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ >> diff --git a/gcc/tree.h b/gcc/tree.h >> index 4859becaa1e7..07eed7219835 100644 >> --- a/gcc/tree.h >> +++ b/gcc/tree.h >> @@ -5619,11 +5619,21 @@ extern tree get_base_address (tree t); >> of EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ >> extern tree array_ref_element_size (tree); >> +/* Give a component_ref that has an array type, return true when an >> + attribute counted_by attached to the corresponding FIELD_DECL. */ >> +extern bool component_ref_has_counted_by_p (tree); >> + >> /* Given a field list, FIELDLIST, of a structure/union, return the FIELD whose >> name is FIELDNAME, return NULL_TREE if such field is not found. >> searching nested anonymous structure/union recursively. */ >> extern tree get_named_field (tree, const char *); >> +/* Give a component_ref that has an array type, return the object that >> + represents its counted_by per the attribute counted_by attached to >> + the corresponding FIELD_DECL. return NULL_TREE when cannot find such >> + object. */ >> +extern tree component_ref_get_counted_by (tree); >> + >> /* Return a typenode for the "standard" C type with a given name. */ >> extern tree get_typenode_from_name (const char *);
diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c new file mode 100644 index 000000000000..ec580c1f1f01 --- /dev/null +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c @@ -0,0 +1,74 @@ +/* test the attribute counted_by and its usage in + * __builtin_dynamic_object_size. */ +/* { dg-do run } */ +/* { dg-options "-O2" } */ + +#include "builtin-object-size-common.h" + +#define expect(p, _v) do { \ + size_t v = _v; \ + if (p == v) \ + __builtin_printf ("ok: %s == %zd\n", #p, p); \ + else \ + { \ + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ + FAIL (); \ + } \ +} while (0); + +struct flex { + int b; + int c[]; +} *array_flex; + +struct annotated { + int b; + int c[] __attribute__ ((counted_by (b))); +} *array_annotated; + +struct nested_annotated { + struct { + union { + int b; + float f; + }; + int n; + }; + int c[] __attribute__ ((counted_by (b))); +} *array_nested_annotated; + +void __attribute__((__noinline__)) setup (int normal_count, int attr_count) +{ + array_flex + = (struct flex *)malloc (sizeof (struct flex) + + normal_count * sizeof (int)); + array_flex->b = normal_count; + + array_annotated + = (struct annotated *)malloc (sizeof (struct annotated) + + attr_count * sizeof (int)); + array_annotated->b = attr_count; + + array_nested_annotated + = (struct nested_annotated *)malloc (sizeof (struct nested_annotated) + + attr_count * sizeof (int)); + array_nested_annotated->b = attr_count; + + return; +} + +void __attribute__((__noinline__)) test () +{ + expect(__builtin_dynamic_object_size(array_flex->c, 1), -1); + expect(__builtin_dynamic_object_size(array_annotated->c, 1), + array_annotated->b * sizeof (int)); + expect(__builtin_dynamic_object_size(array_nested_annotated->c, 1), + array_nested_annotated->b * sizeof (int)); +} + +int main(int argc, char *argv[]) +{ + setup (10,10); + test (); + DONE (); +} diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c new file mode 100644 index 000000000000..a0c3cb88ec71 --- /dev/null +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c @@ -0,0 +1,210 @@ +/* test the attribute counted_by and its usage in +__builtin_dynamic_object_size: what's the correct behavior when the +allocation size mismatched with the value of counted_by attribute? */ +/* { dg-do run } */ +/* { dg-options "-O -fstrict-flex-arrays=3" } */ + +#include "builtin-object-size-common.h" + +struct annotated { + size_t foo; + char others; + char array[] __attribute__((counted_by (foo))); +}; + +#define expect(p, _v) do { \ + size_t v = _v; \ + if (p == v) \ + __builtin_printf ("ok: %s == %zd\n", #p, p); \ + else \ + { \ + __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \ + FAIL (); \ + } \ +} while (0); + +#define noinline __attribute__((__noinline__)) +#define SIZE_BUMP 10 +#define MAX(a, b) ((a) > (b) ? (a) : (b)) +#define MIN(a, b) ((a) < (b) ? (a) : (b)) + +/* In general, Due to type casting, the type for the pointee of a pointer + does not say anything about the object it points to, + So, __builtin_object_size can not directly use the type of the pointee + to decide the size of the object the pointer points to. + + there are only two reliable ways: + A. observed allocations (call to the allocation functions in the routine) + B. observed accesses (read or write access to the location of the + pointer points to) + + that provide information about the type/existence of an object at + the corresponding address. + + for A, we use the "alloc_size" attribute for the corresponding allocation + functions to determine the object size; + + For B, we use the SIZE info of the TYPE attached to the corresponding access. + (We treat counted_by attribute as a complement to the SIZE info of the TYPE + for FMA) + + The only other way in C which ensures that a pointer actually points + to an object of the correct type is 'static': + + void foo(struct P *p[static 1]); + + See https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624814.html + for more details. */ + +/* in the following function, malloc allocated more space than the value + of counted_by attribute. Then what's the correct behavior we expect + the __builtin_dynamic_object_size should have for each of the cases? */ + +static struct annotated * noinline alloc_buf_more (size_t index) +{ + struct annotated *p; + size_t allocated_size + = MAX (sizeof (struct annotated), + (__builtin_offsetof (struct annotated, array[0]) + + (index + SIZE_BUMP) * sizeof (char))); + p = (struct annotated *) malloc (allocated_size); + + p->foo = index; + + /*when checking the observed access p->array, we have info on both + observered allocation and observed access, + A. from observed allocation: + allocated_size - offsetof (struct annotated, array[0]) + B. from observed access: p->foo * sizeof (char) + */ + + /* for size in the whole object: always uses A. */ + /* for size in the sub-object: chose the smaller of A and B. + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html + * for details on why. */ + + /* for MAXIMUM size in the whole object: use the allocation size + for the whole object. */ + expect(__builtin_dynamic_object_size(p->array, 0), + allocated_size - __builtin_offsetof (struct annotated, array[0])); + + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ + expect(__builtin_dynamic_object_size(p->array, 1), + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), + (p->foo) * sizeof(char))); + + /* for MINIMUM size in the whole object: use the allocation size + for the whole object. */ + expect(__builtin_dynamic_object_size(p->array, 2), + allocated_size - __builtin_offsetof (struct annotated, array[0])); + + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ + expect(__builtin_dynamic_object_size(p->array, 3), + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), + (p->foo) * sizeof(char))); + + /*when checking the pointer p, we only have info on the observed allocation. + So, the object size info can only been obtained from the call to malloc. + for both MAXIMUM and MINIMUM: A = (index + SIZE_BUMP) * sizeof (char) */ + expect(__builtin_dynamic_object_size(p, 0), allocated_size); + expect(__builtin_dynamic_object_size(p, 1), allocated_size); + expect(__builtin_dynamic_object_size(p, 2), allocated_size); + expect(__builtin_dynamic_object_size(p, 3), allocated_size); + return p; +} + +/* in the following function, malloc allocated less space than the value + of counted_by attribute. Then what's the correct behavior we expect + the __builtin_dynamic_object_size should have for each of the cases? + NOTE: this is an user error, GCC should issue warnings for such case. + this is a seperate issue we should address later. */ + +static struct annotated * noinline alloc_buf_less (size_t index) +{ + struct annotated *p; + size_t allocated_size + = MAX (sizeof (struct annotated), + (__builtin_offsetof (struct annotated, array[0]) + + (index) * sizeof (char))); + p = (struct annotated *) malloc (allocated_size); + + p->foo = index + SIZE_BUMP; + + /*when checking the observed access p->array, we have info on both + observered allocation and observed access, + A. from observed allocation: + allocated_size - offsetof (struct annotated, array[0]) + B. from observed access: p->foo * sizeof (char) + */ + + /* for size in the whole object: always uses A. */ + /* for size in the sub-object: chose the smaller of A and B. + * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html + * for details on why. */ + + /* for MAXIMUM size in the whole object: use the allocation size + for the whole object. */ + expect(__builtin_dynamic_object_size(p->array, 0), + allocated_size - __builtin_offsetof (struct annotated, array[0])); + + /* for MAXIMUM size in the sub-object. use the smaller of A and B. */ + expect(__builtin_dynamic_object_size(p->array, 1), + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), + (p->foo) * sizeof(char))); + + /* for MINIMUM size in the whole object: use the allocation size + for the whole object. */ + expect(__builtin_dynamic_object_size(p->array, 2), + allocated_size - __builtin_offsetof (struct annotated, array[0])); + + /* for MINIMUM size in the sub-object: use the smaller of A and B. */ + expect(__builtin_dynamic_object_size(p->array, 3), + MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]), + (p->foo) * sizeof(char))); + + /*when checking the pointer p, we only have info on the observed + allocation. So, the object size info can only been obtained from + the call to malloc. */ + expect(__builtin_dynamic_object_size(p, 0), allocated_size); + expect(__builtin_dynamic_object_size(p, 1), allocated_size); + expect(__builtin_dynamic_object_size(p, 2), allocated_size); + expect(__builtin_dynamic_object_size(p, 3), allocated_size); + return p; +} + +int main () +{ + struct annotated *p, *q; + p = alloc_buf_more (10); + q = alloc_buf_less (10); + + /*when checking the observed access p->array, we only have info on the + observed access, i.e, the TYPE_SIZE info from the access. We don't have + info on the whole object. */ + expect(__builtin_dynamic_object_size(p->array, 0), -1); + expect(__builtin_dynamic_object_size(p->array, 1), p->foo * sizeof(char)); + expect(__builtin_dynamic_object_size(p->array, 2), 0); + expect(__builtin_dynamic_object_size(p->array, 3), p->foo * sizeof(char)); + /*when checking the pointer p, we have no observed allocation nor observed + access, therefore, we cannot determine the size info here. */ + expect(__builtin_dynamic_object_size(p, 0), -1); + expect(__builtin_dynamic_object_size(p, 1), -1); + expect(__builtin_dynamic_object_size(p, 2), 0); + expect(__builtin_dynamic_object_size(p, 3), 0); + + /*when checking the observed access p->array, we only have info on the + observed access, i.e, the TYPE_SIZE info from the access. We don't have + info on the whole object. */ + expect(__builtin_dynamic_object_size(q->array, 0), -1); + expect(__builtin_dynamic_object_size(q->array, 1), q->foo * sizeof(char)); + expect(__builtin_dynamic_object_size(q->array, 2), 0); + expect(__builtin_dynamic_object_size(q->array, 3), q->foo * sizeof(char)); + /*when checking the pointer p, we have no observed allocation nor observed + access, therefore, we cannot determine the size info here. */ + expect(__builtin_dynamic_object_size(q, 0), -1); + expect(__builtin_dynamic_object_size(q, 1), -1); + expect(__builtin_dynamic_object_size(q, 2), 0); + expect(__builtin_dynamic_object_size(q, 3), 0); + + DONE (); +} diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc index a62af0500563..cf7843c5684b 100644 --- a/gcc/tree-object-size.cc +++ b/gcc/tree-object-size.cc @@ -585,6 +585,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, if (pt_var != TREE_OPERAND (ptr, 0)) { tree var; + tree counted_by_ref = NULL_TREE; if (object_size_type & OST_SUBOBJECT) { @@ -600,11 +601,12 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, var = TREE_OPERAND (var, 0); if (var != pt_var && TREE_CODE (var) == ARRAY_REF) var = TREE_OPERAND (var, 0); - if (! TYPE_SIZE_UNIT (TREE_TYPE (var)) + if (! component_ref_has_counted_by_p (var) + && ((! TYPE_SIZE_UNIT (TREE_TYPE (var)) || ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var))) || (pt_var_size && TREE_CODE (pt_var_size) == INTEGER_CST && tree_int_cst_lt (pt_var_size, - TYPE_SIZE_UNIT (TREE_TYPE (var))))) + TYPE_SIZE_UNIT (TREE_TYPE (var))))))) var = pt_var; else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF) { @@ -612,6 +614,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, /* For &X->fld, compute object size if fld isn't a flexible array member. */ bool is_flexible_array_mem_ref = false; + while (v && v != pt_var) switch (TREE_CODE (v)) { @@ -660,6 +663,8 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, /* Now the ref is to an array type. */ gcc_assert (TREE_CODE (TREE_TYPE (v)) == ARRAY_TYPE); is_flexible_array_mem_ref = array_ref_flexible_size_p (v); + counted_by_ref = component_ref_get_counted_by (v); + while (v != pt_var && TREE_CODE (v) == COMPONENT_REF) if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0))) != UNION_TYPE @@ -673,8 +678,11 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, == RECORD_TYPE) { /* compute object size only if v is not a - flexible array member. */ - if (!is_flexible_array_mem_ref) + flexible array member or the flexible array member + has a known element count indicated by the user + through attribute counted_by. */ + if (!is_flexible_array_mem_ref + || counted_by_ref) { v = NULL_TREE; break; @@ -707,9 +715,24 @@ addr_object_size (struct object_size_info *osi, const_tree ptr, if (var != pt_var) { - var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); - if (!TREE_CONSTANT (var_size)) - var_size = get_or_create_ssa_default_def (cfun, var_size); + if (!counted_by_ref) + { + var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); + if (!TREE_CONSTANT (var_size)) + var_size = get_or_create_ssa_default_def (cfun, var_size); + } + else + { + gcc_assert (TREE_CODE (var) == COMPONENT_REF + && TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE); + tree element_size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (var))); + var_size + = size_binop (MULT_EXPR, + fold_convert (sizetype, counted_by_ref), + fold_convert (sizetype, element_size)); + if (!todo) + todo = TODO_update_ssa_only_virtuals; + } if (!var_size) return false; } diff --git a/gcc/tree.cc b/gcc/tree.cc index fcd36ae0cd74..3b6ddcbdcbf8 100644 --- a/gcc/tree.cc +++ b/gcc/tree.cc @@ -12745,6 +12745,32 @@ array_ref_element_size (tree exp) return SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (elmt_type), exp); } +/* For a component_ref that has an array type ARRAY_REF, return TRUE when + an counted_by attribute attached to the corresponding FIELD_DECL. + return FALSE otherwise. */ +bool +component_ref_has_counted_by_p (tree array_ref) +{ + if (TREE_CODE (array_ref) != COMPONENT_REF) + return false; + + if (TREE_CODE (TREE_TYPE (array_ref)) != ARRAY_TYPE) + return false; + + tree struct_object = TREE_OPERAND (array_ref, 0); + tree struct_type = TREE_TYPE (struct_object); + + if (!RECORD_OR_UNION_TYPE_P (struct_type)) + return false; + tree field_decl = TREE_OPERAND (array_ref, 1); + tree attr_counted_by = lookup_attribute ("counted_by", + DECL_ATTRIBUTES (field_decl)); + + if (!attr_counted_by) + return false; + return true; +} + /* Given a field list, FIELDLIST, of a structure/union, return a TREE_LIST, with each TREE_VALUE a FIELD_DECL stepping down the chain to the FIELD whose name is FIELDNAME, which is the last TREE_VALUE of the list. @@ -12771,7 +12797,7 @@ get_named_field (tree fieldlist, const char *fieldname) fields inside it recursively. */ else if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (field))) if ((named_field = get_named_field (TYPE_FIELDS (TREE_TYPE (field)), - fieldname)) != NULL_TREE) + fieldname)) != NULL_TREE) { named_field = tree_cons (NULL_TREE, field, named_field); break; @@ -12784,6 +12810,73 @@ get_named_field (tree fieldlist, const char *fieldname) return named_field; } +/* For a component_ref that has an array type ARRAY_REF, get the object that + represents its counted_by per the attribute counted_by attached to + the corresponding FIELD_DECL. return NULL_TREE when cannot find such + object. + For example, if: + + struct P { + int k; + int x[] __attribute__ ((counted_by (k))); + } *p; + + for the following reference: + + p->x[b] + + the object that represents its element count will be: + + p->k + + So, when component_ref_get_counted_by (p->x[b]) is called, p->k should be + returned. +*/ + +tree +component_ref_get_counted_by (tree array_ref) +{ + if (! component_ref_has_counted_by_p (array_ref)) + return NULL_TREE; + + tree struct_object = TREE_OPERAND (array_ref, 0); + tree struct_type = TREE_TYPE (struct_object); + tree field_decl = TREE_OPERAND (array_ref, 1); + tree attr_counted_by = lookup_attribute ("counted_by", + DECL_ATTRIBUTES (field_decl)); + gcc_assert (attr_counted_by); + + /* If there is an counted_by attribute attached to the field, + get the field that maps to the counted_by. */ + + const char *fieldname + = IDENTIFIER_POINTER (TREE_VALUE (TREE_VALUE (attr_counted_by))); + + tree counted_by_field = get_named_field (TYPE_FIELDS (struct_type), + fieldname); + + gcc_assert (counted_by_field); + + /* generate the tree node that represent the counted_by of this array + ref. This is a (possible nested) COMPONENT_REF to the counted_by_field + of the containing structure. */ + + tree counted_by_ref = NULL_TREE; + tree object = struct_object; + do + { + tree field = TREE_VALUE (counted_by_field); + + counted_by_ref = build3 (COMPONENT_REF, + TREE_TYPE (field), + unshare_expr (object), field, + NULL_TREE); + object = counted_by_ref; + counted_by_field = TREE_CHAIN (counted_by_field); + } + while (counted_by_field); + return counted_by_ref; +} /* Return a tree representing the lower bound of the array mentioned in EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ diff --git a/gcc/tree.h b/gcc/tree.h index 4859becaa1e7..07eed7219835 100644 --- a/gcc/tree.h +++ b/gcc/tree.h @@ -5619,11 +5619,21 @@ extern tree get_base_address (tree t); of EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */ extern tree array_ref_element_size (tree); +/* Give a component_ref that has an array type, return true when an + attribute counted_by attached to the corresponding FIELD_DECL. */ +extern bool component_ref_has_counted_by_p (tree); + /* Given a field list, FIELDLIST, of a structure/union, return the FIELD whose name is FIELDNAME, return NULL_TREE if such field is not found. searching nested anonymous structure/union recursively. */ extern tree get_named_field (tree, const char *); +/* Give a component_ref that has an array type, return the object that + represents its counted_by per the attribute counted_by attached to + the corresponding FIELD_DECL. return NULL_TREE when cannot find such + object. */ +extern tree component_ref_get_counted_by (tree); + /* Return a typenode for the "standard" C type with a given name. */ extern tree get_typenode_from_name (const char *);