https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94389
Bug ID: 94389
Summary: __attribute__((warn_unused_result)) will warn if the
result is discarded as an optimisation
Product: gcc
Version: 9.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: felix.von.s at posteo dot de
Target Milestone: ---
With the code below, the compiler warns about an unused result, even though the
result is used:
#define O_TEXT 0 /* defined on Windows and DOS, but not needed on Unix */
__attribute__((warn_unused_result))
extern int text_mode(void);
int get_flags(void) {
return text_mode() ? O_TEXT : 0;
}
Similarly, there is a warning if the result of a function marked with
__attribute__((warn_unused_result)) is multiplied by 0, and probably with other
expressions that are easily constant-folded. If the function also has
__attribute__((const)), there is no warning.
I think this issue could be resolved as a by-product of fixing bug 66425.
