| Summary: | Incorrect message description of -Wunused-value | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Chengnian Sun <chengniansun> |
| Component: | c | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | NEW --- | ||
| Severity: | normal | CC: | manu |
| Priority: | P3 | Keywords: | diagnostic |
| Version: | 5.0 | ||
| Target Milestone: | --- | ||
| See Also: | https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107797 | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | 2015-01-18 00:00:00 | |
| Bug Depends on: | |||
| Bug Blocks: | 89180 | ||
(a = 0) >= 0; gets transformed into (a = 0); , 1; This is some undesired early folding. Hopefully we'll sort it out in GCC 6. |
GCC emits a -Wunused-value warning with a wrong description for the expression "(a = 0) >= 0". There is no comma expression, but the message is right-hand operand of comma expression has no effect If I change the operator from ">=" to "!=", then the message is correct. $: cat t.c int a; void f() { (a = 0) != 0; (a = 0) >= 0; } $: $: gcc-trunk -c -Wunused-value t.c t.c: In function ‘f’: t.c:3:11: warning: value computed is not used [-Wunused-value] (a = 0) != 0; ^ t.c:4:11: warning: right-hand operand of comma expression has no effect [-Wunused-value] (a = 0) >= 0; ^ $: $: clang-trunk -c -Wunused-value t.c t.c:3:11: warning: inequality comparison result unused [-Wunused-comparison] (a = 0) != 0; ~~~~~~~~^~~~ t.c:4:11: warning: relational comparison result unused [-Wunused-comparison] (a = 0) >= 0; ~~~~~~~~^~~~ 2 warnings generated. $: