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From: "antiquarktv at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/97748] New: Preincrement of _Complex gives bogus warning =
 "value computed is not used"
Date: Fri, 06 Nov 2020 23:21:27 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97748

            Bug ID: 97748
           Summary: Preincrement of _Complex gives bogus warning =3D "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 comp=
uted
is not used".  The value is in fact used, thus the warning is bogus.=20

 #include <stdio.h>
 #include <complex.h>
 int main()
 {
        double _Complex x =3D 2.0 + I * 2.0;
        ++x;
        printf("%f,%f\n", creal(x), cimag(x));
 }

Output:

gcc -Wall  test.c
test.c: In function =E2=80=98main=E2=80=99:
test.c:7:2: warning: value computed is not used [-Wunused-value]
    7 |  ++x;
      |  ^~~=