https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106264
Bug ID: 106264
Summary: spurious -Wunused-value on a folded frexp, modf, and
remquo calls with unused result
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
In C mode only the following test case triggers the invalid (or at least poorly
worded and so confusing) instances of -Wunused-value. Each instance goes away
when the call is not folded or when its result is used. The C++ front end
doesn't warn.
$ cat a.c && gcc -O -Wall -S -Wall a.c
double frexp (double, int*);
double modf (double, double*);
double remquo (double, double, int*);
int f (void)
{
int y;
frexp (1.0, &y);
return y;
}
double g (void)
{
double y;
modf (1.0, &y);
return y;
}
int h (void)
{
int y;
remquo (1.0, 1.0, &y);
return y;
}
a.c: In function ‘f’:
a.c:8:3: warning: right-hand operand of comma expression has no effect
[-Wunused-value]
8 | frexp (1.0, &y);
| ^~~~~~~~~~~~~~~
a.c: In function ‘g’:
a.c:15:3: warning: right-hand operand of comma expression has no effect
[-Wunused-value]
15 | modf (1.0, &y);
| ^~~~~~~~~~~~~~
a.c: In function ‘h’:
a.c:22:3: warning: right-hand operand of comma expression has no effect
[-Wunused-value]
22 | remquo (1.0, 1.0, &y);
| ^~~~~~~~~~~~~~~~~~~~~
