[PATCH] 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 <[email protected]>
Signed-off-by: Ondrej Marek <[email protected]>
---
 v4:
 - introduce minor changes based on the review
 resource/Makefile        |   1 +
 resource/tst-getrusage.c | 125 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 126 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..4caa1bed42
--- /dev/null
+++ b/resource/tst-getrusage.c
@@ -0,0 +1,125 @@
+/* Test of the getrusage function.
+   Copyright (C) 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 <support/xunistd.h>
+#include <sys/wait.h>
+#include <benchtests/bench-util.h>
+#include <array_length.h>
+
+static void
+do_work (void)
+{
+  uint64_t sink = 0;
+  for (uint64_t i = 0; i < UINT64_C (1000000); i++)
+    {
+      sink += i;
+      DO_NOT_OPTIMIZE_OUT (sink);
+    }
+}
+
+static void
+get_child_elapsed_time (long *result)
+{
+  pid_t pid;
+  pid = xfork ();
+
+  if (pid > 0)
+    {
+      int status;
+      xwaitpid (pid, &status, 0);
+      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;
+    }
+  else
+    {
+      /* Simulate some work. */
+      do_work ();
+      _exit (0);
+    }
+}
+
+static void
+test_getrusage_children (void)
+{
+  long elapsed_time_before;
+  long elapsed_time_after;
+
+  get_child_elapsed_time (&elapsed_time_before);
+  get_child_elapsed_time (&elapsed_time_after);
+  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;
+  TEST_VERIFY_EXIT (elapsed_time_before >= 0);
+
+  /* Simulate some work */
+  do_work ();
+
+  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)
+{
+  test_getrusage (RUSAGE_SELF);
+#ifdef RUSAGE_THREAD
+  test_getrusage (RUSAGE_THREAD);
+#endif
+
+  /* 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);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.47.3