1 files changed, 82 insertions, 0 deletions
diff --git a/stdlib/tst-realpath.c b/stdlib/tst-realpath.c
new file mode 100644
index 0000000000..2ae5e4fb2b
--- /dev/null
+++ b/stdlib/tst-realpath.c
@@ -0,0 +1,82 @@
+/* Test to verify that realpath() doesn't cause false positives due
+   to GCC attribute malloc.
+
+   Test failure exposes the presence of the attribute in the following
+   declaration:
+
+   __attribute__ ((__malloc__ (free, 1))) char*
+   realpath (const char *, char *);
+
+   Copyright (C) 2021 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 <stdio.h>
+#include <stdlib.h>
+#include <malloc.h>
+
+#if defined __GNUC__ && __GNUC__ >= 11
+/* Turn GCC -Wmismatched-dealloc warnings into errors to expose false
+   positives.  */
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic error "-Wmismatched-dealloc"
+
+/* Associate dealloc as the only deallocator suitable for pointers
+   returned from alloc.
+   GCC automatically disables inlining of allocator and deallocator
+   functions marked with the argument form of attribute malloc but
+   it doesn't hurt to disable it explicitly.  */
+__attribute  ((noipa)) void dealloc (void *);
+__attribute ((malloc (dealloc, 1))) char* alloc (void);
+#endif
+
+void dealloc (void *p)
+{
+  free (p);
+}
+
+char* alloc (void)
+{
+  return (char *)malloc (8);
+}
+
+static int
+do_test (void)
+{
+  char *resolved_path = alloc ();
+  char *ret = realpath ("/", resolved_path);
+  dealloc (ret);
+
+  resolved_path = alloc ();
+  ret = realpath ("/", resolved_path);
+  dealloc (resolved_path);
+
+  /* The following should emit a warning (but doesn't with GCC 11):
+     resolved_path = alloc ();
+     ret = realpath ("/", resolved_path);
+     free (ret);   // expect -Wmismatched-dealloc
+  */
+
+  return 0;
+}
+
+#if defined __GNUC__ && __GNUC__ >= 11
+/* Restore -Wmismatched-dealloc setting.  */
+#  pragma GCC diagnostic pop
+#endif
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"