| Message ID | 20240918183517.517366-1-polacek@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: tweak for -Wrange-loop-construct [PR116731] | expand |
On 9/18/24 2:35 PM, Marek Polacek wrote: > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? OK. > -- >8 -- > This PR reports that the warning would be better off using a check > for trivially constructible rather than trivially copyable. > > LLVM accepted a similar fix: > https://github.com/llvm/llvm-project/issues/47355 > > PR c++/116731 > > gcc/cp/ChangeLog: > > * parser.cc (warn_for_range_copy): Check if TYPE is trivially > constructible, not copyable. > > gcc/testsuite/ChangeLog: > > * g++.dg/warn/Wrange-loop-construct3.C: New test. > --- > gcc/cp/parser.cc | 8 ++- > .../g++.dg/warn/Wrange-loop-construct3.C | 57 +++++++++++++++++++ > 2 files changed, 62 insertions(+), 3 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/warn/Wrange-loop-construct3.C > > diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc > index 4dd9474cf60..140457ba224 100644 > --- a/gcc/cp/parser.cc > +++ b/gcc/cp/parser.cc > @@ -14394,11 +14394,13 @@ warn_for_range_copy (tree decl, tree expr) > else if (!CP_TYPE_CONST_P (type)) > return; > > - /* Since small trivially copyable types are cheap to copy, we suppress the > - warning for them. 64B is a common size of a cache line. */ > + /* Since small trivially constructible types are cheap to construct, we > + suppress the warning for them. 64B is a common size of a cache line. */ > + tree vec = make_tree_vec (1); > + TREE_VEC_ELT (vec, 0) = TREE_TYPE (expr); > if (TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST > || (tree_to_uhwi (TYPE_SIZE_UNIT (type)) <= 64 > - && trivially_copyable_p (type))) > + && is_trivially_xible (INIT_EXPR, type, vec))) > return; > > /* If we can initialize a reference directly, suggest that to avoid the > diff --git a/gcc/testsuite/g++.dg/warn/Wrange-loop-construct3.C b/gcc/testsuite/g++.dg/warn/Wrange-loop-construct3.C > new file mode 100644 > index 00000000000..3d9d0c9088e > --- /dev/null > +++ b/gcc/testsuite/g++.dg/warn/Wrange-loop-construct3.C > @@ -0,0 +1,57 @@ > +// PR c++/116731 > +// { dg-do compile { target c++11 } } > +// { dg-options "-Wrange-loop-construct" } > + > +void > +f0 () > +{ > + struct S { > + char a[64]; > + S& operator=(const S&) { return *this; }; > + }; > + > + S arr[8]; > + for (const auto r : arr) > + (void) r; > +} > + > +void > +f1 () > +{ > + struct S { > + char a[65]; > + S& operator=(const S&) { return *this; }; > + }; > + > + S arr[8]; > + for (const auto r : arr) // { dg-warning "creates a copy" } > + (void) r; > +} > + > +void > +f2 () > +{ > + struct S { > + char a[64]; > + S& operator=(const S&) { return *this; }; > + ~S() { } > + }; > + > + S arr[8]; > + for (const auto r : arr) // { dg-warning "creates a copy" } > + (void) r; > +} > + > +void > +f3 () > +{ > + struct S { > + char a[65]; > + S& operator=(const S&) { return *this; }; > + ~S() { } > + }; > + > + S arr[8]; > + for (const auto r : arr) // { dg-warning "creates a copy" } > + (void) r; > +} > > base-commit: cc62b2c3da118f08f71d2ae9c08bafb55b35767a
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc index 4dd9474cf60..140457ba224 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -14394,11 +14394,13 @@ warn_for_range_copy (tree decl, tree expr) else if (!CP_TYPE_CONST_P (type)) return; - /* Since small trivially copyable types are cheap to copy, we suppress the - warning for them. 64B is a common size of a cache line. */ + /* Since small trivially constructible types are cheap to construct, we + suppress the warning for them. 64B is a common size of a cache line. */ + tree vec = make_tree_vec (1); + TREE_VEC_ELT (vec, 0) = TREE_TYPE (expr); if (TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST || (tree_to_uhwi (TYPE_SIZE_UNIT (type)) <= 64 - && trivially_copyable_p (type))) + && is_trivially_xible (INIT_EXPR, type, vec))) return; /* If we can initialize a reference directly, suggest that to avoid the diff --git a/gcc/testsuite/g++.dg/warn/Wrange-loop-construct3.C b/gcc/testsuite/g++.dg/warn/Wrange-loop-construct3.C new file mode 100644 index 00000000000..3d9d0c9088e --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wrange-loop-construct3.C @@ -0,0 +1,57 @@ +// PR c++/116731 +// { dg-do compile { target c++11 } } +// { dg-options "-Wrange-loop-construct" } + +void +f0 () +{ + struct S { + char a[64]; + S& operator=(const S&) { return *this; }; + }; + + S arr[8]; + for (const auto r : arr) + (void) r; +} + +void +f1 () +{ + struct S { + char a[65]; + S& operator=(const S&) { return *this; }; + }; + + S arr[8]; + for (const auto r : arr) // { dg-warning "creates a copy" } + (void) r; +} + +void +f2 () +{ + struct S { + char a[64]; + S& operator=(const S&) { return *this; }; + ~S() { } + }; + + S arr[8]; + for (const auto r : arr) // { dg-warning "creates a copy" } + (void) r; +} + +void +f3 () +{ + struct S { + char a[65]; + S& operator=(const S&) { return *this; }; + ~S() { } + }; + + S arr[8]; + for (const auto r : arr) // { dg-warning "creates a copy" } + (void) r; +}