http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59871
Bug ID: 59871
Summary: No unused value warning for comma expression
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: chengniansun at gmail dot com
I have a return statement with a comma expression -- "return fn2(), 1, 0;".
Gcc should warn that the "1" in the middle is not used as it does not have any
side effect.
The following is the detailed instructions to reproduce the issue.
$: cat s.c
extern int fn2();
int fn1() {
return fn2(), 1, 0;
}
$: gcc-trunk -Wall -Wextra -c -std=c99 -pedantic s.c
$: gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/home/chengniansun/tools/gcc-trunk-binaries/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --enable-languages=c,c++
--disable-multilib --prefix=/home/chengniansun/tools/gcc-trunk-binaries
Thread model: posix
gcc version 4.9.0 20140109 (experimental) (GCC)
$: clang-trunk -Wall -Wextra -c -std=c99 -pedantic s.c
s.c:3:18: warning: expression result unused [-Wunused-value]
return fn2(), 1, 0;
^
1 warning generated.
