https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110793
Bug ID: 110793
Summary: regression in optimizing unused string
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: barry.revzin at gmail dot com
Target Milestone: ---
Consider this reduced, silly-looking example:
#include <string>
inline int zero(std::string const& = {}) { return 0; }
int main() {
return zero();
}
In several versions of gcc (12.2, 11.4, 10.5), this simply compiles to:
main:
xor eax, eax
ret
But in 13.1 (C++17, but not C++20), we get:
main:
sub rsp, 40
lea rax, [rsp+16]
mov rdi, rsp
mov BYTE PTR [rsp+16], 0
mov QWORD PTR [rsp], rax
mov QWORD PTR [rsp+8], 0
call std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> >::_M_dispose()
xor eax, eax
add rsp, 40
ret
Notably, 13.1 C++20 and C++23 also compiles to just xor.
I'm not sure if this is a language or library issue, so tagging it language for
now.
