On Thu, Jan 28, 2021 at 02:50:10PM +0800, Sun Ke wrote:
> when run make, show:
> swapon.c:135:3: warning: 'p' may be used uninitialized in this function
> [-Wmaybe-uninitialized]
> memcpy(p, buf, BUF_SIZE);
> ^~~~~~~~~~~~~~~~~~~~~~~~
> fix it.
If you don't have a situation to prove this's a real bug, I guess the gcc might
think the 'p' can be used uninitialized at here when verb is TEST_MWRITE_BEFORE_AND_MWRITE_AFTER:
case TEST_MWRITE_BEFORE_AND_MWRITE_AFTER:
memcpy(p, buf, BUF_SIZE);
break;
But from the code logic, if verb is TEST_MWRITE_BEFORE_AND_MWRITE_AFTER, the 'p'
will be initialized by:
switch (verb) {
case TEST_MWRITE_BEFORE_AND_MWRITE_AFTER:
case TEST_MWRITE_BEFORE:
p = mmap(NULL, BUF_SIZE, PROT_WRITE | PROT_READ, MAP_SHARED,
So I think this's a fake uninitialized warning (Maybe I'm wrong. But if I'm right,
better to specify that in commit log).
Anyway, I personally don't object to initialize a pointer to NULL at beginning,
and make a build warning disappear. Leave the decision to maintainer :)
Thanks,
Zorro
>
> Signed-off-by: Sun Ke <sunke32@xxxxxxxxxx>
> ---
> src/swapon.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/swapon.c b/src/swapon.c
> index afaed405..fe8949a3 100644
> --- a/src/swapon.c
> +++ b/src/swapon.c
> @@ -41,7 +41,7 @@ int main(int argc, char **argv)
> .sa_handler = handle_signal,
> };
> enum verbs verb = TEST_SWAPON;
> - void *p;
> + void *p = NULL;
> ssize_t sz;
> int fd = -1;
> int ret, c;
> --
> 2.13.6
>
