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c++: -Wdangling-reference tweak to unbreak aarch64

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My recent -Wdangling-reference change to not warn on std::span-like classes
unfortunately caused a new warning: extending reference_like_class_p also
opens the door to new warnings since we use reference_like_class_p for
checking the return type of the function: either it must be a reference
or a reference_like_class_p.

We can consider even non-templates as std::span-like to get rid of the
warning here.

gcc/cp/ChangeLog:

	* call.cc (reference_like_class_p): Consider even non-templates for
	std::span-like classes.

gcc/ChangeLog:

	* doc/invoke.texi: Update -Wdangling-reference documentation.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wdangling-reference21.C: New test.
This commit is contained in:
Marek Polacek 2024-02-01 16:11:43 -05:00
parent 44764984cf
commit 8efcdbf59b
3 changed files with 48 additions and 6 deletions
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8
gcc/cp/call.cc
View file

@ -14082,8 +14082,8 @@ reference_like_class_p (tree ctype)
return true;
}
/* Avoid warning if CTYPE looks like std::span: it's a class template,
has a T* member, and a trivial destructor. For example,
/* Avoid warning if CTYPE looks like std::span: it has a T* member and
a trivial destructor. For example,
template<typename T>
struct Span {
@ -14092,9 +14092,7 @@ reference_like_class_p (tree ctype)
};
is considered std::span-like. */
if (NON_UNION_CLASS_TYPE_P (ctype)
&& CLASSTYPE_TEMPLATE_INSTANTIATION (ctype)
&& TYPE_HAS_TRIVIAL_DESTRUCTOR (ctype))
if (NON_UNION_CLASS_TYPE_P (ctype) && TYPE_HAS_TRIVIAL_DESTRUCTOR (ctype))
for (tree field = next_aggregate_field (TYPE_FIELDS (ctype));
field; field = next_aggregate_field (DECL_CHAIN (field)))
if (TYPE_PTR_P (TREE_TYPE (field)))

2
gcc/doc/invoke.texi
View file

@ -3929,7 +3929,7 @@ struct Span @{
@};
@end smallexample
as @code{std::span}-like; that is, the class is a non-union class template
as @code{std::span}-like; that is, the class is a non-union class
that has a pointer data member and a trivial destructor.
This warning is enabled by @option{-Wall}.

44
gcc/testsuite/g++.dg/warn/Wdangling-reference21.C Normal file
View file

@ -0,0 +1,44 @@
// { dg-do compile { target c++11 } }
// { dg-options "-Wdangling-reference" }
// Reduced from config/aarch64/aarch64-early-ra.cc.
template <typename T> struct array_slice {
using iterator = T *;
iterator begin();
iterator end();
iterator m_base;
};
struct allocno_group_info { };
char recog_data_2;
int record_constraints_op;
struct early_ra {
using operand_mask = int;
struct allocno_info {
int is_earlyclobbered;
};
struct allocno_subgroup {
array_slice<allocno_info> allocnos();
allocno_group_info *group;
};
allocno_subgroup get_allocno_subgroup(int);
void record_constraints();
};
void early_ra::record_constraints() {
operand_mask earlyclobber_operands, matched_operands, unmatched_operands,
matches_operands, op_mask = operand_mask();
auto record_operand = [&](int, int) {
operand_mask overlaps;
matches_operands |= overlaps;
};
for (int opno = 0; recog_data_2; ++opno) {
operand_mask op_mask = earlyclobber_operands |= op_mask;
if (0)
record_operand(1, 0);
}
if (op_mask || (matched_operands & unmatched_operands && 0))
for (auto &allocno : get_allocno_subgroup(record_constraints_op).allocnos())
allocno.is_earlyclobbered = true;
}