[Bug libstdc++/79349] unused std::string is not optimized away in presense of a call

[hiraditya at msn dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79349

AK <hiraditya at msn dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |NEW
         Resolution|WORKSFORME                  |---

--- Comment #3 from AK <hiraditya at msn dot com> ---
(In reply to AK from comment #2)
> The problem is exceptions. When I compile without exceptions
> (-fno-exceptions) g++ does optimize this away and gives same output as
> clang. It seems clang++ compiles without exceptions by default and behaves
> like g++ when -fexceptions is passed.

Correction:
For the example:
#include<string>

int main() {
  std::string s("abc");
  return 0;
}

clang (with libc++) optimizes away the std::string even in the presence of
exceptions (-fexceptions). When I compile without exceptions (-fno-exceptions)
g++ does optimize the std::string away.


However, when I introduce a call:

#include<string>

void foo();

int main() {
  std::string s("abc");
  foo();
  return 0;
}

clang++ still optimizes the std::string but g++ does not. I think the problem
is with libstdc++ because when clang is using libstdc++ I can see the
destructor.


Sorry for the confusion.