[Bug c/86584] New: Incorrect -Wsequence-point warning on structure member

[rusty at rustcorp dot com.au]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86584

            Bug ID: 86584
           Summary: Incorrect -Wsequence-point warning on structure member
           Product: gcc
           Version: 7.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rusty at rustcorp dot com.au
  Target Milestone: ---

gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0, x86-64.  Also in gcc-8 (Ubuntu
8.1.0-1ubuntu1) 8.1.0.

I have a macro which does an assignment, and also hands the address of the same
var to the function.  The reduced version is below: it gives a spurious warning
when the var involved is a struct member:

struct s {
        int f;
};

void func(int *f, int);

int main(void)
{
        struct s s;
        int f;

        /* bad-warning-gcc.c:13:17: warning: operation on ‘s.f’ may be
undefined [-Wsequence-point] */
        func(&s.f, s.f = 1);
        /* No warning for this */
        func(&f, f = 1);
        return 0;
}