[Bug c/97748] New: Preincrement of _Complex gives bogus warning = "value computed is not used"

[antiquarktv at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97748

            Bug ID: 97748
           Summary: Preincrement of _Complex gives bogus warning = "value
                    computed is not used"
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antiquarktv at gmail dot com
  Target Milestone: ---

The following code, when compiled with -Wall, gives the warning "value computed
is not used".  The value is in fact used, thus the warning is bogus. 

 #include <stdio.h>
 #include <complex.h>
 int main()
 {
        double _Complex x = 2.0 + I * 2.0;
        ++x;
        printf("%f,%f\n", creal(x), cimag(x));
 }

Output:

gcc -Wall  test.c
test.c: In function ‘main’:
test.c:7:2: warning: value computed is not used [-Wunused-value]
    7 |  ++x;
      |  ^~~