Re: [pacman-dev] [PATCH 2/2] Avoid false warning from gcc-6

On 04/05/16 23:08, Dave Reisner wrote:

On Wed, May 04, 2016 at 05:42:29PM +1000, Allan McRae wrote:

...

The value EAGAIN is allowed by POSIX to be the same as EWOULDBLOCK, but this is not guaranteed. Thus on some systems (e.g. glibc Linux), we get a warning that the logical OR is being performed on two expressions of the same type. We can not get rid of this test in case any system defines these as unique values.

Use a pragma block to prevent any gcc warning on these tests.

Signed-off-by: Allan McRae --- lib/libalpm/util.c | 8 ++++++++ 1 file changed, 8 insertions(+)

diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c index 4a4847d..e105786 100644 --- a/lib/libalpm/util.c +++ b/lib/libalpm/util.c @@ -476,7 +476,11 @@ static int _alpm_chroot_write_to_child(alpm_handle_t *handle, int fd, /* write was successful, remove the written data from the buffer */ *buf_size -= nwrite; memmove(buf, buf + nwrite, *buf_size); + +/* EAGAIN may be the same value as EWOULDBLOCK (POSIX.1) - prevent GCC warning */ +#pragma GCC diagnostic ignored "-Wlogical-op" } else if(errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) { +#pragma GCC diagnostic pop

Instead of repeating this pragma (and the comparison for that matter), why not just wrap it in a separate function? Something like:

int should_retry(int errnum) { return errnum == EAGAIN #if EAGAIN != EWOULDBLOCK || errnum == EWOULDBLOCK #endif || errnum == EINTR; }

POSIX requires that constants in errno.h are defined as macros "and which shall be suitable for use in #if pre-processing directives".

Much better way of handling this. Thanks! A