[09/12] Add a test for multiple makecontext calls

diff --git a/ChangeLog b/ChangeLog
index d387465f29..18329df423 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@ 
+2018-07-25  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* stdlib/Makefile (tests): Add tst-swapcontext1.
+	* stdlib/tst-swapcontext1.c: New test.
+
 2018-07-25  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/x86/Makefile (tests): Add tst-cet-legacy-1,
diff --git a/stdlib/Makefile b/stdlib/Makefile
index b5e55b0a55..bc8929f2b9 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..7802df4868
--- /dev/null
+++ b/stdlib/tst-swapcontext1.c
@@ -0,0 +1,108 @@ 
+/* Check multiple makecontext calls.
+   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 <stdlib.h>
+#include <ucontext.h>
+
+static ucontext_t uctx_main, uctx_func1, uctx_func2;
+const char *str1 = "\e[31mswapcontext(&uctx_func1, &uctx_main)\e[0m";
+const char *str2 = "\e[34mswapcontext(&uctx_func2, &uctx_main)\e[0m";
+const char *fmt1 = "\e[31m";
+const char *fmt2 = "\e[34m";
+
+#define handle_error(msg) \
+  do { perror(msg); exit(EXIT_FAILURE); } while (0)
+
+__attribute__((noinline, noclone))
+static void
+func4(ucontext_t *uocp, ucontext_t *ucp, const char *str, const char *fmt)
+{
+  printf("      %sfunc4: %s\e[0m\n", fmt, str);
+  if (swapcontext(uocp, ucp) == -1)
+    handle_error("swapcontext");
+  printf("      %sfunc4: returning\e[0m\n", fmt);
+}
+
+__attribute__((noinline, noclone))
+static void
+func3(ucontext_t *uocp, ucontext_t *ucp, const char *str, const char *fmt)
+{
+  printf("    %sfunc3: func4(uocp, ucp, str)\e[0m\n", fmt);
+  func4(uocp, ucp, str, fmt);
+  printf("    %sfunc3: returning\e[0m\n", fmt);
+}
+
+__attribute__((noinline, noclone))
+static void
+func1(void)
+{
+  while ( 1 )
+    {
+      printf("  \e[31mfunc1: func3(&uctx_func1, &uctx_main, str1)\e[0m\n");
+      func3( &uctx_func1, &uctx_main, str1, fmt1);
+    }
+}
+
+__attribute__((noinline, noclone))
+static void
+func2(void)
+{
+  while ( 1 )
+    {
+      printf("  \e[34mfunc2: func3(&uctx_func2, &uctx_main, str2)\e[0m\n");
+      func3(&uctx_func2, &uctx_main, str2, fmt2);
+    }
+}
+
+static int
+do_test (void)
+{
+  char func1_stack[16384];
+  char func2_stack[16384];
+  int i;
+
+  if (getcontext(&uctx_func1) == -1)
+    handle_error("getcontext");
+  uctx_func1.uc_stack.ss_sp = func1_stack;
+  uctx_func1.uc_stack.ss_size = sizeof(func1_stack);
+  uctx_func1.uc_link = &uctx_main;
+  makecontext(&uctx_func1, func1, 0);
+
+  if (getcontext(&uctx_func2) == -1)
+    handle_error("getcontext");
+  uctx_func2.uc_stack.ss_sp = func2_stack;
+  uctx_func2.uc_stack.ss_size = sizeof(func2_stack);
+  uctx_func2.uc_link = &uctx_func1;
+  makecontext(&uctx_func2, func2, 0);
+
+  for ( i = 0; i < 4; i++ )
+    {
+      if (swapcontext(&uctx_main, &uctx_func1) == -1)
+	handle_error("swapcontext");
+      printf("        \e[35mmain: swapcontext(&uctx_main, &uctx_func2)\n\e[0m");
+      if (swapcontext(&uctx_main, &uctx_func2) == -1)
+	handle_error("swapcontext");
+      printf("        \e[35mmain: swapcontext(&uctx_main, &uctx_func1)\n\e[0m");
+    }
+
+  printf("main: exiting\n");
+  exit(EXIT_SUCCESS);
+}
+
+#include <support/test-driver.c>