Fix build warnings in resolv/res_send.c
Commit Message
Hi,
this patch fixes the gcc warnings seen with gcc 9 -march>=z13 on s390x:
res_send.c: In function ‘__res_context_send’:
res_send.c:498:7: error: ‘resplen’ may be used uninitialized in this
function [-Werror=maybe-uninitialized]
498 | if (n == 0 && (buf2 == NULL || *resplen2 == 0))
| ^
In this case send_vc is inlined into __res_context_send
and the maybe uninitialized resplen belongs to the one in send_vc.
In send_vc there is already a DIAG_IGNORE_NEEDS_COMMENT (5,
"-Wmaybe-uninitialized")
and a comment which explains that this is a false-positive.
Note that resplen is used as return value.
This patch adds a further DIAG_IGNORE_NEEDS_COMMENT around the
declaration of n
in __res_context_send and the comparison after n was set to the return
value of send_vc.
Bye
Stefan
ChangeLog:
* resolv/res_send.c (__res_context_send):
Disable maybe-uninitialized warning.
Comments
On 6/25/19 3:18 PM, Stefan Liebler wrote:
> Hi,
>
> this patch fixes the gcc warnings seen with gcc 9 -march>=z13 on s390x:
> res_send.c: In function ‘__res_context_send’:
> res_send.c:498:7: error: ‘resplen’ may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
> 498 | if (n == 0 && (buf2 == NULL || *resplen2 == 0))
> | ^
>
> In this case send_vc is inlined into __res_context_send
> and the maybe uninitialized resplen belongs to the one in send_vc.
>
> In send_vc there is already a DIAG_IGNORE_NEEDS_COMMENT (5,
> "-Wmaybe-uninitialized")
> and a comment which explains that this is a false-positive.
> Note that resplen is used as return value.
>
> This patch adds a further DIAG_IGNORE_NEEDS_COMMENT around the
> declaration of n
> in __res_context_send and the comparison after n was set to the return
> value of send_vc.
>
> Bye
> Stefan
>
> ChangeLog:
>
> * resolv/res_send.c (__res_context_send):
> Disable maybe-uninitialized warning.
ping
commit 6c3b01619ec2260a95bb7651e9c3a7aa3619745b
Author: Stefan Liebler <stli@linux.ibm.com>
Date: Tue Jun 25 13:59:28 2019 +0200
Fix build warnings in resolv/res_send.c
This patch fixes the gcc warnings seen with gcc 9 -march>=z13 on s390x:
res_send.c: In function ‘__res_context_send’:
res_send.c:498:7: error: ‘resplen’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
498 | if (n == 0 && (buf2 == NULL || *resplen2 == 0))
| ^
In this case send_vc is inlined into __res_context_send
and the maybe uninitialized resplen belongs to the one in send_vc.
In send_vc there is already a DIAG_IGNORE_NEEDS_COMMENT (5, "-Wmaybe-uninitialized")
and a comment which explains that this is a false-positive.
Note that resplen is used as return value.
This patch adds a further DIAG_IGNORE_NEEDS_COMMENT around the declaration of n
in __res_context_send and the comparison after n was set to the return value of send_vc.
ChangeLog:
* resolv/res_send.c (__res_context_send): Disable maybe-uninitialized warning.
@@ -401,7 +401,18 @@ __res_context_send (struct resolv_context *ctx,
int *nansp2, int *resplen2, int *ansp2_malloced)
{
struct __res_state *statp = ctx->resp;
- int gotsomewhere, terrno, try, v_circuit, resplen, n;
+ int gotsomewhere, terrno, try, v_circuit, resplen;
+ /* On some architectures send_vc is inlined and the compiler might emit
+ a warning indicating 'resplen' may be used uninitialized. Note that
+ the warning belongs to resplen in send_vc which is used as return
+ value! There the maybe-uninitialized warning is already ignored as
+ it is a false-positive - see comment in send_vc.
+ Here the variable n is set to the return value of send_vc.
+ See below. */
+ DIAG_PUSH_NEEDS_COMMENT;
+ DIAG_IGNORE_NEEDS_COMMENT (9, "-Wmaybe-uninitialized");
+ int n;
+ DIAG_POP_NEEDS_COMMENT;
if (statp->nscount == 0) {
__set_errno (ESRCH);
@@ -495,8 +506,12 @@ __res_context_send (struct resolv_context *ctx,
ansp2_malloced);
if (n < 0)
return (-1);
+ /* See comment at the declaration of n. */
+ DIAG_PUSH_NEEDS_COMMENT;
+ DIAG_IGNORE_NEEDS_COMMENT (9, "-Wmaybe-uninitialized");
if (n == 0 && (buf2 == NULL || *resplen2 == 0))
goto next_ns;
+ DIAG_POP_NEEDS_COMMENT;
} else {
/* Use datagrams. */
n = send_dg(statp, buf, buflen, buf2, buflen2,