[PATCH] getrusage: Add smoke test for getrusage

[Ondrej Marek]

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 ();
+
+  if (pid == -1)
+    {
+      perror ("Fork failed");
+      return 1;
+    }
+  else if (pid > 0)
+    {
+      int status;
+      if (waitpid (pid, &status, 0) == -1)
+        {
+          perror ("waitpid");
+          return 1;
+        }
+
+      if (!WIFEXITED (status))
+        {
+          puts ("An error occured in the child process\n");
+          return 1;
+        }
+
+      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;
+      }
+
+      _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;
+  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++)
+    {
+      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>
-- 
2.47.3