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devmapper_wrapper.go: fix gcc warning

I am getting the following warning from gcc when compiling the daemon:

> # github.com/docker/docker/pkg/devicemapper
> pkg/devicemapper/devmapper_wrapper.go: In function ‘log_cb’:
> pkg/devicemapper/devmapper_wrapper.go:20:2: warning: ignoring return
> value of ‘vasprintf’, declared with attribute warn_unused_result
> [-Wunused-result]
> vasprintf(&buffer, f, ap);
> ^

vasprintf(3) man page says if the function returns -1, the buffer is
undefined, so we should not use it. In practice, I assume, this never
happens so we just return.

Introduced by https://github.com/moby/moby/pull/33845 that resulted in
commit 63328c6 ("devicemapper: remove 256 character limit of libdm logs")

Cc: Aleksa Sarai <asarai@suse.de>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

Kir Kolyshkin authored on 2017/07/18 09:40:29
Showing 1 changed files

pkg/devicemapper/devmapper_wrapper.go

History View file @ 7da12bc

@@ -15,10 +15,15 @@ static void	log_cb(int level, const char *file, int line, int dm_errno_or_class,
+                     {
                      	char *buffer = NULL;
                      	va_list ap;
                     +	int ret;
                      	va_start(ap, f);
                     -	vasprintf(&buffer, f, ap);
                     +	ret = vasprintf(&buffer, f, ap);
                      	va_end(ap);
                     +	if (ret < 0) {
                     +		// memory allocation failed -- should never happen?
                     +		return;
                     +	}
                      	DevmapperLogCallback(level, (char *)file, line, dm_errno_or_class, buffer);
                      	free(buffer);