https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49974
--- Comment #17 from Jonathan Wakely <redi at gcc dot gnu.org> ---
95911 boils down to this:
#include <utility>
struct X { int i = 0; };
X&& f(X&& x) { return std::move(x); }
int main()
{
X&& x = f(X{});
return x.i;
}
With recent releases we get a -Wuninitialized warning, which isn't entirely
correct, but at least suggests a problem:
49974.cc: In function 'int main()':
49974.cc:10:12: warning: '<anonymous>.X::i' is used uninitialized
[-Wuninitialized]
10 | return x.i;
| ^
49974.cc:9:15: note: '<anonymous>' declared here
9 | X&& x = f(X{});
| ^
(the note is new in GCC 11).
With -fsanitize=address we get a nice stack-use-after-scope error:
==3088273==ERROR: AddressSanitizer: stack-use-after-scope on address
0x7fff976ed520 at pc 0x000000401100 bp 0x7fff976ed4f0 sp 0x7fff976ed4e8
READ of size 4 at 0x7fff976ed520 thread T0
#0 0x4010ff in main /tmp/49974.cc:10
#1 0x7fd157d181a2 in __libc_start_main ../csu/libc-start.c:308
#2 0x40116d in _start (/tmp/a.out+0x40116d)
