getrusage: Add smoke test for getrusage

  Add smoke test verifying that getrusage returns non-negative user time and fails with invalid who value.

Co-authored-by: Frantisek Cech <fr.cech@proton.me>
Signed-off-by: Ondrej Marek <ondrejm4rek@gmail.com>
---
 v2:
 - use volatile variables to prevent compiler from optimizing away the loop
 - RUSAGE_CHILDREN test forks new processes
 - use both fields of timeval struct for elapsed time comparison
 resource/Makefile        |   1 +
 resource/tst-getrusage.c | 139 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 140 insertions(+)
 create mode 100644 resource/tst-getrusage.c
  

On 27/06/26 09:48, Ondrej Marek wrote:
> Add smoke test verifying that getrusage returns non-negative user time and fails with invalid who value.
> 
> Co-authored-by: Frantisek Cech <fr.cech@proton.me>
> Signed-off-by: Ondrej Marek <ondrejm4rek@gmail.com>
> ---
>  v2:
>  - use volatile variables to prevent compiler from optimizing away the loop
>  - RUSAGE_CHILDREN test forks new processes
>  - use both fields of timeval struct for elapsed time comparison
>  resource/Makefile        |   1 +
>  resource/tst-getrusage.c | 139 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 140 insertions(+)
>  create mode 100644 resource/tst-getrusage.c
> 
> diff --git a/resource/Makefile b/resource/Makefile
> index 589b73f44f..dac48434dd 100644
> --- a/resource/Makefile
> +++ b/resource/Makefile
> @@ -28,6 +28,7 @@ routines := getrlimit setrlimit getrlimit64 setrlimit64 getrusage ulimit      \
>  tests := \
>    bug-ulimit1 \
>    tst-getrlimit \
> +  tst-getrusage \
>  # tests
>  
>  
> diff --git a/resource/tst-getrusage.c b/resource/tst-getrusage.c
> new file mode 100644
> index 0000000000..c50456b9bc
> --- /dev/null
> +++ b/resource/tst-getrusage.c
> @@ -0,0 +1,139 @@
> +/* Test of the getrusage function.
> +   Copyright (C) 2005-2026 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <errno.h>
> +#include <stdio.h>
> +#include <sys/resource.h>
> +#include <stdint.h>
> +#include <support/check.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +#include <sys/wait.h>
> +
> +static int
> +get_child_elapsed_time (long *result)
> +{
> +  pid_t pid;
> +  pid = fork ();

Use xfork here.

> +
> +  if (pid == -1)
> +    {
> +      perror ("Fork failed");
> +      return 1;
> +    }
> +  else if (pid > 0)
> +    {
> +      int status;
> +      if (waitpid (pid, &status, 0) == -1)
> +        {
> +          perror ("waitpid");
> +          return 1;
> +        }

And xwaitpid.

> +
> +      if (!WIFEXITED (status))
> +        {
> +          puts ("An error occured in the child process\n");
> +          return 1;
> +        }

And TEST_VERIFY_EXIT (WIFEXITED (status));

> +
> +      struct rusage rusage = { 0 };
> +
> +      int ret_val = getrusage (RUSAGE_CHILDREN, &rusage);
> +      TEST_VERIFY_EXIT (ret_val == 0);
> +      long elapsed_time = (rusage.ru_utime.tv_sec * 1000000L) + rusage.ru_utime.tv_usec;
> +      TEST_VERIFY_EXIT (elapsed_time >= 0);
> +
> +      *result = elapsed_time;
> +      return 0;
> +    }
> +  else
> +    {
> +      /* Simulate some work */
> +      volatile unsigned long long sink = 0;
> +
> +      for (unsigned long long i = 0; i < 1000000000ULL; i++) {
> +        sink += i;
> +      }

We have the macro DO_NOT_OPTIMIZE_OUT (benchtests/bench-util.h), which are used for
similar constructs.  Maybe move this to somewhere in include and do:

  uint64_t sink = 0;
  for (uint64_t i = 0; i < UINT64_C(1000000000); i++)
    {
      sink += i;
      DO_NOT_OPTIMIZE_OUT (sink);
    }

> +
> +      _exit(0);
> +    }
> +}
> +
> +static void
> +test_getrusage_children (void)
> +{
> +  long elapsed_time_before;
> +  long elapsed_time_after;
> +
> +  int ret_val = get_child_elapsed_time (&elapsed_time_before);
> +  TEST_VERIFY_EXIT (ret_val == 0);
> +  int ret_val2 = get_child_elapsed_time (&elapsed_time_after);
> +  TEST_VERIFY_EXIT (ret_val2 == 0);
> +  TEST_VERIFY_EXIT (elapsed_time_after >= elapsed_time_before);
> +}
> +
> +static void
> +test_getrusage (int who)
> +{
> +  struct rusage before_usage = { 0 };
> +  struct rusage after_usage = { 0 };
> +
> +  int ret_val = getrusage (who, &before_usage);
> +  TEST_VERIFY_EXIT (ret_val == 0);
> +  long elapsed_time_before = (before_usage.ru_utime.tv_sec * 1000000L) + before_usage.ru_utime.tv_usec;

Line too long, use clang-format with the .clang-format we now have.

> +  TEST_VERIFY_EXIT (elapsed_time_before >= 0);
> +
> +  /* Simulate some work */
> +  volatile unsigned long long sink = 0;
> +
> +  for (unsigned long long i = 0; i < 1000000000ULL; i++)
> +    {
> +      sink += i;
> +    }
> +
> +  int ret_val2 = getrusage (who, &after_usage);
> +  TEST_VERIFY_EXIT (ret_val2 == 0);
> +
> +  long elapsed_time_after = (after_usage.ru_utime.tv_sec * 1000000L) + after_usage.ru_utime.tv_usec;
> +  TEST_VERIFY_EXIT (elapsed_time_after >= elapsed_time_before);
> +}
> +
> +static int
> +do_test (void)
> +{
> +  int whos[] = { RUSAGE_SELF, RUSAGE_THREAD };
> +  for (int i = 0; i < sizeof (whos) / sizeof (int); i++)

Use array_length (...).

> +    {
> +      int who = whos[i];
> +      test_getrusage (who);
> +    }
> +
> +  /* RUSAGE_CHILDREN test case with forking children */
> +  test_getrusage_children ();
> +
> +  /* Invalid who value test case */
> +  struct rusage usage_struct = { 0 };
> +  int invalid_who = 999;
> +  int ret_val = getrusage (invalid_who, &usage_struct);
> +  TEST_VERIFY (ret_val == -1);
> +
> +  puts ("Everything OK\n");
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>

The rest looks ok.