https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109232
Bug ID: 109232
Summary: Using deduced return type in an unevaluated context
leads to codegen
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rs2740 at gmail dot com
Target Milestone: ---
auto begin(auto&& r) {
return r.begin();
}
namespace {
struct R {
int* begin();
};
}
static_assert(__is_same(decltype(begin(R())), int*));
int main() {}
Even though ::begin is only used in an unevaluated context, GCC at -O0
generates code for begin<R>, leading to a warning and a failure to link
(https://gcc.godbolt.org/z/cdajoP7f3):
<source>:10:14: warning: 'int* {anonymous}::R::begin()' used but never defined
10 | int* begin();
| ^~~~~
/opt/compiler-explorer/gcc-trunk-20230320/bin/../lib/gcc/x86_64-linux-gnu/13.0.1/../../../../x86_64-linux-gnu/bin/ld:
/tmp/cc7gqEhh.o: in function `auto begin<(anonymous namespace)::R&>((anonymous
namespace)::R&)':
<source>:2: undefined reference to `(anonymous namespace)::R::begin()'
collect2: error: ld returned 1 exit status
Execution build compiler returned: 1
