[PATCH] tcp: Avoid comparison of expressions with different signedness in tcp_timer_handler()

[PATCH] tcp: Avoid comparison of expressions with different signedness in tcp_timer_handler()

[Stefano Brivio]

With gcc 14.2, building against musl 1.2.5 (slightly outdated Alpine
on x86_64):

tcp.c: In function 'tcp_timer_handler':
util.h:40:39: warning: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Wsign-compare]
   40 | #define MIN(x, y)               (((x) < (y)) ? (x) : (y))
      |                                       ^
tcp.c:2593:31: note: in expansion of macro 'MIN'
 2593 |                         max = MIN(TCP_MAX_RETRIES, max);
      |                               ^~~
util.h:40:54: warning: operand of '?:' changes signedness from 'int' to 'unsigned int' due to unsignedness of other operand [-Wsign-compare]
   40 | #define MIN(x, y)               (((x) < (y)) ? (x) : (y))
      |                                                      ^~~
tcp.c:2593:31: note: in expansion of macro 'MIN'
 2593 |                         max = MIN(TCP_MAX_RETRIES, max);
      |                               ^~~

for some reason, that's not reported by gcc with glibc.

Make the temporary 'max' variable unsigned, as we know it can't be
negative anyway.

While at it, add the customary blank line between variable
declarations and code.

Fixes: 3dde0e07804e ("tcp: Update data retransmission timeout")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 tcp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tcp.c b/tcp.c
index 88ad886..68c92da 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2588,7 +2588,8 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref)
 		tcp_timer_ctl(c, conn);
 	} else if (conn->flags & ACK_FROM_TAP_DUE) {
 		if (!(conn->events & ESTABLISHED)) {
-			int max;
+			unsigned int max;
+
 			max = c->tcp.syn_retries + c->tcp.syn_linear_timeouts;
 			max = MIN(TCP_MAX_RETRIES, max);
 			if (conn->retries >= max) {
-- 
2.43.0

Re: [PATCH] tcp: Avoid comparison of expressions with different signedness in tcp_timer_handler()

[David Gibson]

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On Wed, Mar 04, 2026 at 05:32:03PM +0100, Stefano Brivio wrote:
> With gcc 14.2, building against musl 1.2.5 (slightly outdated Alpine
> on x86_64):
> 
> tcp.c: In function 'tcp_timer_handler':
> util.h:40:39: warning: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Wsign-compare]
>    40 | #define MIN(x, y)               (((x) < (y)) ? (x) : (y))
>       |                                       ^
> tcp.c:2593:31: note: in expansion of macro 'MIN'
>  2593 |                         max = MIN(TCP_MAX_RETRIES, max);
>       |                               ^~~
> util.h:40:54: warning: operand of '?:' changes signedness from 'int' to 'unsigned int' due to unsignedness of other operand [-Wsign-compare]
>    40 | #define MIN(x, y)               (((x) < (y)) ? (x) : (y))
>       |                                                      ^~~
> tcp.c:2593:31: note: in expansion of macro 'MIN'
>  2593 |                         max = MIN(TCP_MAX_RETRIES, max);
>       |                               ^~~
> 
> for some reason, that's not reported by gcc with glibc.
> 
> Make the temporary 'max' variable unsigned, as we know it can't be
> negative anyway.
> 
> While at it, add the customary blank line between variable
> declarations and code.
> 
> Fixes: 3dde0e07804e ("tcp: Update data retransmission timeout")
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  tcp.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 88ad886..68c92da 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -2588,7 +2588,8 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref)
>  		tcp_timer_ctl(c, conn);
>  	} else if (conn->flags & ACK_FROM_TAP_DUE) {
>  		if (!(conn->events & ESTABLISHED)) {
> -			int max;
> +			unsigned int max;
> +
>  			max = c->tcp.syn_retries + c->tcp.syn_linear_timeouts;
>  			max = MIN(TCP_MAX_RETRIES, max);
>  			if (conn->retries >= max) {
> -- 
> 2.43.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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