[1/5] Add a test for swapcontext with a wrapper

diff --git a/stdlib/Makefile b/stdlib/Makefile
index 808a8ceab7..ef90f77689 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -84,7 +84,8 @@  tests		:= tst-strtol tst-strtod testmb testrand testsort testdiv   \
 		   tst-cxa_atexit tst-on_exit test-atexit-race 		    \
 		   test-at_quick_exit-race test-cxa_atexit-race             \
 		   test-on_exit-race test-dlclose-exit-race 		    \
-		   tst-makecontext-align test-bz22786 tst-strtod-nan-sign
+		   tst-makecontext-align test-bz22786 tst-strtod-nan-sign \
+		   tst-swapcontext1
 
 tests-internal	:= tst-strtod1i tst-strtod3 tst-strtod4 tst-strtod5i \
 		   tst-tls-atexit tst-tls-atexit-nodelete
diff --git a/stdlib/tst-swapcontext1.c b/stdlib/tst-swapcontext1.c
new file mode 100644
index 0000000000..2ffbecd4a2
--- /dev/null
+++ b/stdlib/tst-swapcontext1.c
@@ -0,0 +1,91 @@ 
+/* Check swapcontext wrapper.
+   Modified from c-c++-common/asan/swapcontext-test-1.c in GCC testsuite.
+   Copyright (C) 2018 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <ucontext.h>
+#include <unistd.h>
+
+__attribute__((noinline, noclone))
+int
+myswapcontext (ucontext_t *oucp, ucontext_t *ucp)
+{
+  int res = swapcontext (oucp, ucp);
+  return res;
+}
+
+ucontext_t orig_context;
+ucontext_t child_context;
+
+void
+Child (int mode)
+{
+  char x[32] = {0};  /* Stack gets poisoned. */
+  printf("Child: %p\n", x);
+  /* (a) Do nothing, just return to parent function.
+     (b) Jump into the original function. Stack remains poisoned unless we do
+     something. */
+  if (mode == 1)
+    {
+      if (myswapcontext (&child_context, &orig_context) < 0)
+	{
+	  perror ("swapcontext");
+	  _exit (0);
+	}
+    }
+}
+
+int
+Run (int arg, int mode)
+{
+  int i;
+  const int kStackSize = 1 << 20;
+  char child_stack[kStackSize + 1];
+  printf ("Child stack: %p\n", child_stack);
+  /* Setup child context. */
+  getcontext (&child_context);
+  child_context.uc_stack.ss_sp = child_stack;
+  child_context.uc_stack.ss_size = kStackSize / 2;
+  if (mode == 0)
+    child_context.uc_link = &orig_context;
+  makecontext (&child_context, (void (*)(void))Child, 1, mode);
+  if (myswapcontext (&orig_context, &child_context) < 0)
+    {
+      perror("swapcontext");
+      return 0;
+    }
+  /* Touch childs's stack to make sure it's unpoisoned. */
+  for (i = 0; i < kStackSize; i++)
+    child_stack[i] = i;
+  return child_stack[arg];
+}
+
+volatile int zero = 0;
+
+static int
+do_test (void)
+{
+  int ret = 0;
+  ret += Run (zero, 0);
+  fprintf (stderr, "Test1 passed\n");
+  ret += Run (zero, 1);
+  fprintf (stderr, "Test2 passed\n");
+  return ret;
+}
+
+#include <support/test-driver.c>