| Message ID | 20240422221841.3531740-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: constexpr union member access folding [PR114709] | expand |
On 4/22/24 15:18, Patrick Palka wrote: > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK > for trunk/13/12? OK with a rationale comment. > -- >8 -- > > The object/offset canonicalization performed in cxx_fold_indirect_ref > is undesirable for union member accesses because it loses information > about the member being accessed which we may later need to diagnose an > inactive-member access. So this patch restricts the canonicalization > accordingly. > > PR c++/114709 > > gcc/cp/ChangeLog: > > * constexpr.cc (cxx_fold_indirect_ref): Restrict object/offset > canonicalization to RECORD_TYPE member accesses. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp0x/constexpr-union8.C: New test. > --- > gcc/cp/constexpr.cc | 1 + > gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C | 8 ++++++++ > 2 files changed, 9 insertions(+) > create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc > index fcc847d85df..941a478e889 100644 > --- a/gcc/cp/constexpr.cc > +++ b/gcc/cp/constexpr.cc > @@ -5797,6 +5797,7 @@ cxx_fold_indirect_ref (const constexpr_ctx *ctx, location_t loc, tree type, > more folding opportunities. */ > auto canonicalize_obj_off = [] (tree& obj, tree& off) { > while (TREE_CODE (obj) == COMPONENT_REF > + && TREE_CODE (TREE_TYPE (TREE_OPERAND (obj, 0))) == RECORD_TYPE > && (tree_int_cst_sign_bit (off) || integer_zerop (off))) > { > tree field = TREE_OPERAND (obj, 1); > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C > new file mode 100644 > index 00000000000..34c264944b6 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C > @@ -0,0 +1,8 @@ > +// PR c++/114709 > +// { dg-do compile { target c++11 } } > + > +struct T1 { int a, b; }; > +struct T2 { int c; double d; }; > +union U { T1 t1; T2 t2; }; > + > +constexpr int v = U{{1,2}}.t2.*&T2::c; // { dg-error "accessing 'U::t2'" }
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index fcc847d85df..941a478e889 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -5797,6 +5797,7 @@ cxx_fold_indirect_ref (const constexpr_ctx *ctx, location_t loc, tree type, more folding opportunities. */ auto canonicalize_obj_off = [] (tree& obj, tree& off) { while (TREE_CODE (obj) == COMPONENT_REF + && TREE_CODE (TREE_TYPE (TREE_OPERAND (obj, 0))) == RECORD_TYPE && (tree_int_cst_sign_bit (off) || integer_zerop (off))) { tree field = TREE_OPERAND (obj, 1); diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C new file mode 100644 index 00000000000..34c264944b6 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-union8.C @@ -0,0 +1,8 @@ +// PR c++/114709 +// { dg-do compile { target c++11 } } + +struct T1 { int a, b; }; +struct T2 { int c; double d; }; +union U { T1 t1; T2 t2; }; + +constexpr int v = U{{1,2}}.t2.*&T2::c; // { dg-error "accessing 'U::t2'" }