[Bug c++/104702] New: [12 Regression] False positive -Wunused-value warning with -fno-exceptions

[dani at danielbertalan dot dev via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104702

            Bug ID: 104702
           Summary: [12 Regression] False positive -Wunused-value warning
                    with -fno-exceptions
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dani at danielbertalan dot dev
  Target Milestone: ---

I'm getting a false positive "value computed is not used" warning on trunk iff
I specify -fno-exceptions.

Godbolt link: https://godbolt.org/z/h7ssrza8Y

$ cat unused.cpp
struct FlyString {
  FlyString(char const*);
  ~FlyString();
};

struct Array { FlyString __data[1]; };

void frobnicate(Array&);

int main() {
    Array s_reserved_words { "" };
    frobnicate(s_reserved_words);
}

$ g++ -fno-exceptions -Wunused-value unused.cpp
unused.cpp: In function 'int main()':
unused.cpp:11:33: warning: value computed is not used [-Wunused-value]
   11 |     Array s_reserved_words { "" };
      |                                 ^