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servers: silence -Wunused-result with pragma

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In some configurations the `write()` functions gets the
`warn_unused_result` attribute, that makes casting to `(void)`
ineffective to silence this warning. Seen with glibc, in 5 CI jobs.
The warning option appeared in GCC 4.5 and comes enabled by default.

```
tests/server/util.c:329:5: error: ignoring return value of ‘write’ declared with attribute ‘warn_unused_result’ [-Werror=unused-result]
  329 |     write(STDERR_FILENO, msg, sizeof(msg) - 1);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
Ref: https://github.com/curl/curl/actions/runs/27548333990/job/81427544632

Refs:
https://github.com/curl/curl/pull/22023#issuecomment-4708455631
https://gcc.gnu.org/onlinedocs/gcc-16.1.0/gcc/Warning-Options.html#index-Wunused-result
https://gcc.gnu.org/onlinedocs/gcc-16.1.0/gcc/Common-Attributes.html#index-warn_005funused_005fresult
https://stackoverflow.com/questions/40576003/ignoring-warning-wunused-result

Follow-up to c8d8f081fd #22023
Follow-up to e95f509c66 #16852

Closes #22034
This commit is contained in:
Viktor Szakats 2026-06-15 21:27:51 +02:00
parent 5687d211c4
commit 526d3b8a53
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1 changed files with 15 additions and 10 deletions
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25
tests/server/util.c
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@ -313,22 +313,25 @@ static HWND hidden_main_window = NULL;
* should finish its execution in a controlled manner as soon as possible.
* The first time this is called it sets got_exit_signal to 1 and
* stores in exit_signal the signal that triggered its execution.
*/
/*
*
* Only call signal-safe functions from the signal handler, as required by
* the POSIX specification:
* https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
* Hence, do not call 'logmsg()', and instead use 'open/write/close' to
* log errors.
*/
static size_t useless; /* to silence variable 'rc' set but not used */
/* suppress warnings seen in configurations where 'write()' has the attribute
'warn_unused_result', which is not silenced by casting to '(void)'. */
#if defined(CURL_HAVE_DIAG) && !defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-result" /* GCC 4.5+ */
#endif
static void exit_signal_handler(int signum)
{
int old_errno = errno;
size_t rc = 0;
if(!serverlogfile) {
static const char msg[] = "exit_signal_handler: serverlogfile not set\n";
rc = write(STDERR_FILENO, msg, sizeof(msg) - 1);
(void)write(STDERR_FILENO, msg, sizeof(msg) - 1);
}
else {
int fd = -1;
@ -342,14 +345,14 @@ static void exit_signal_handler(int signum)
if(fd != -1) {
#endif
static const char msg[] = "exit_signal_handler: called\n";
rc = write(fd, msg, sizeof(msg) - 1);
(void)write(fd, msg, sizeof(msg) - 1);
curlx_close(fd);
}
else {
static const char msg[] = "exit_signal_handler: failed opening ";
rc = write(STDERR_FILENO, msg, sizeof(msg) - 1);
rc += write(STDERR_FILENO, serverlogfile, strlen(serverlogfile));
rc += write(STDERR_FILENO, "\n", 1);
(void)write(STDERR_FILENO, msg, sizeof(msg) - 1);
(void)write(STDERR_FILENO, serverlogfile, strlen(serverlogfile));
(void)write(STDERR_FILENO, "\n", 1);
}
}
if(got_exit_signal == 0) {
@ -360,10 +363,12 @@ static void exit_signal_handler(int signum)
(void)SetEvent(exit_event);
#endif
}
useless = rc;
(void)signal(signum, exit_signal_handler);
errno = old_errno;
}
#if defined(CURL_HAVE_DIAG) && !defined(__clang__)
#pragma GCC diagnostic pop
#endif
#ifdef _WIN32
/* CTRL event handler for Windows Console applications to simulate