glib/tests: Add test to check that we abort on low-memory

In case we're out of memory we should abort after having printed an error
message, this is similar to crashing but not exactly the same, so ensure
we exit for SIGABRT and not because of a SIGSEV.

We use a test wrapper to ensure that both the exit code and the stderr
match what we expected.

glib/tests/meson.build

@@ -291,6 +291,15 @@ test_extra_programs = {
   'test-spawn-echo' : {},
 }
 
+if have_dlopen_dlsym
+  test_extra_programs += {
+    'messages-low-memory' : {
+      'dependencies' : libdl_dep,
+      'override_options' : ['b_asneeded=false'],
+    },
+  }
+endif
+
 if host_machine.system() == 'windows'
   # test-spawn-sleep helper binary required by the spawn tests above
   test_extra_programs += {
@@ -334,6 +343,7 @@ foreach program_name, extra_args : test_extra_programs
       sources: [source, extra_sources],
       c_args : test_cargs,
       cpp_args: test_cpp_args,
+      override_options : extra_args.get('override_options', []),
       dependencies : test_deps + extra_args.get('dependencies', []),
       install_dir : installed_tests_execdir,
       install_tag : 'tests',
@@ -367,6 +377,7 @@ foreach test_name, extra_args : glib_tests
     c_args : test_cargs + extra_args.get('c_args', []),
     cpp_args : test_cpp_args + extra_args.get('cpp_args', []),
     link_args : extra_args.get('link_args', []),
+    override_options : extra_args.get('override_options', []),
     dependencies : test_deps + extra_args.get('dependencies', []),
     install_dir: installed_tests_execdir,
     install_tag: 'tests',
@@ -409,6 +420,14 @@ python_tests = {
   },
 }
 
+if 'messages-low-memory' in test_extra_programs
+  python_tests += {
+    'messages-low-memory.py' : {
+      'extra_programs': ['messages-low-memory'],
+    },
+  }
+endif
+
 foreach test_name, extra_args : python_tests
   depends = [extra_args.get('depends', [])]
   suite = ['glib', 'no-valgrind']

glib/tests/messages-low-memory.c

@@ -0,0 +1,88 @@
+/* Unit tests for gmessages on low-memory
+ *
+ * Copyright (C) 2022 Marco Trevisan
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This 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.
+ *
+ * This 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 this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Marco Trevisan <marco.trevisan@canonical.com>
+ */
+
+#include "config.h"
+
+#include <dlfcn.h>
+#include <glib.h>
+
+static gboolean malloc_eom = FALSE;
+static gboolean our_malloc_called = FALSE;
+
+#ifdef ENOMEM
+/* Wrapper around malloc() which returns `ENOMEM` if the test variable
+ * `malloc_eom` is set.
+ * Otherwise passes through to the normal malloc() in libc.
+ */
+
+void *
+malloc (size_t size)
+{
+  static void *(*real_malloc)(size_t);
+  if (!real_malloc)
+      real_malloc = dlsym (RTLD_NEXT, "malloc");
+
+  if (malloc_eom)
+    {
+      our_malloc_called = TRUE;
+      errno = ENOMEM;
+      return NULL;
+    }
+
+  return real_malloc (size);
+}
+#endif
+
+int
+main (int   argc,
+      char *argv[])
+{
+  g_setenv ("LC_ALL", "C", TRUE);
+
+#ifndef ENOMEM
+  g_message ("ENOMEM Not defined, test skipped");
+  return 77;
+#endif
+
+  g_message ("Simulates a situation in which we were crashing because "
+             "of low-memory, leading malloc to fail instead of aborting");
+  g_message ("bug: https://gitlab.gnome.org/GNOME/glib/-/issues/2753");
+
+  /* Setting `malloc_eom` to true should cause the override `malloc()`
+   * in this file to fail on the allocation on the next line. */
+  malloc_eom = TRUE;
+  g_message ("Memory is exhausted, but we'll write anyway: %u", 123);
+
+#ifndef __linux__
+  if (!our_malloc_called)
+    {
+      /* For some reasons this doesn't work darwin systems, so ignore the result
+       * for non-linux, while we want to ensure the test is valid at least there
+       */
+      g_message ("Our malloc implementation has not been called, the test "
+                 "has not been performed");
+      return 77;
+    }
+#endif
+
+  return 0;
+}

glib/tests/messages-low-memory.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+#
+# Copyright © 2022 Emmanuel Fleury <emmanuel.fleury@gmail.com>
+# Copyright © 2022 Marco Trevisan <mail@3v1n0.net>
+#
+# This 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.
+#
+# This 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 this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+# MA  02110-1301  USA
+
+""" Integration tests for g_message functions on low-memory. """
+
+import collections
+import os
+import subprocess
+import unittest
+
+import taptestrunner
+
+Result = collections.namedtuple("Result", ("info", "out", "err"))
+
+
+class TestMessagesLowMemory(unittest.TestCase):
+    """Integration test for checking g_message()’s behavior on low memory.
+
+    This can be run when installed or uninstalled. When uninstalled,
+    it requires G_TEST_BUILDDIR and G_TEST_SRCDIR to be set.
+
+    The idea with this test harness is to test if g_message and friends
+    assert instead of crashing if memory is exhausted, printing the expected
+    error message.
+    """
+
+    test_binary = "messages-low-memory"
+
+    def setUp(self):
+        ext = ""
+        if os.name == "nt":
+            ext = ".exe"
+        if "G_TEST_BUILDDIR" in os.environ:
+            self._test_binary = os.path.join(
+                os.environ["G_TEST_BUILDDIR"], self.test_binary + ext
+            )
+        else:
+            self._test_binary = os.path.join(
+                os.path.dirname(__file__), self.test_binary + ext
+            )
+        print("messages-low-memory:", self._test_binary)
+
+    def runTestBinary(self, *args):
+        print("Running:", *args)
+
+        env = os.environ.copy()
+        env["LC_ALL"] = "C.UTF-8"
+        print("Environment:", env)
+
+        # We want to ensure consistent line endings...
+        info = subprocess.run(
+            *args,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            env=env,
+            universal_newlines=True,
+        )
+        out = info.stdout.strip()
+        err = info.stderr.strip()
+
+        result = Result(info, out, err)
+
+        print("Return code:", result.info.returncode)
+        print("Output:", result.out)
+        print("Error:", result.err)
+        return result
+
+    def test_message_memory_allocation_failure(self):
+        """Test running g_message() when memory is exhausted."""
+        result = self.runTestBinary(self._test_binary)
+
+        if result.info.returncode == 77:
+            self.skipTest("Not supported")
+
+        if os.name == "nt":
+            self.assertEqual(result.info.returncode, 3)
+        else:
+            self.assertEqual(result.info.returncode, -6)
+        self.assertIn("failed to allocate memory", result.err)
+
+
+if __name__ == "__main__":
+    unittest.main(testRunner=taptestrunner.TAPTestRunner())