C++11 thread_local destructors support

This feature is specifically for the C++ compiler to offload calling
thread_local object destructors on thread program exit, to glibc.
This is to overcome the possible complication of destructors of
thread_local objects getting called after the DSO in which they're
defined is unloaded by the dynamic linker.  The DSO is marked as
'unloadable' if it has a constructed thread_local object and marked as
'unloadable' again when all the constructed thread_local objects
defined in it are destroyed.

1 files changed, 111 insertions, 0 deletions

diff --git a/stdlib/tst-tls-atexit.c b/stdlib/tst-tls-atexit.c
new file mode 100644
index 0000000..b7312cb
--- /dev/null
+++ b/stdlib/tst-tls-atexit.c
@@ -0,0 +1,111 @@
+/* Verify that DSO is unloaded only if its TLS objects are destroyed.
+   Copyright (C) 2012 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/>.  */
+
+/* There are two tests in this test case.  The first is implicit where it is
+   assumed that the destructor call on exit of the LOAD function does not
+   segfault.  The other is a verification that after the thread has exited, a
+   dlclose will unload the DSO.  */
+
+#include <dlfcn.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+void *handle;
+pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
+
+void *
+load (void *u)
+{
+  pthread_mutex_lock (&m);
+  handle = dlopen ("$ORIGIN/tst-tls-atexit-lib.so", RTLD_LAZY);
+  if (!handle)
+    {
+      printf ("Unable to load DSO: %s\n", dlerror ());
+      return (void *) (uintptr_t) 1;
+    }
+
+  void (*foo) (void) = (void (*) (void)) dlsym(handle, "do_foo");
+
+  if (!foo)
+    {
+      printf ("Unable to find symbol: %s\n", dlerror ());
+      exit (1);
+    }
+
+  foo ();
+
+  /* This should not unload the DSO.  If it does, then the thread exit will
+     result in a segfault.  */
+  dlclose (handle);
+  pthread_mutex_unlock (&m);
+
+  return NULL;
+}
+
+int
+main (void)
+{
+  pthread_t t;
+  int ret;
+  void *thr_ret;
+
+  if ((ret = pthread_create (&t, NULL, load, NULL)) != 0)
+    {
+      printf ("pthread_create failed: %s\n", strerror (ret));
+      return 1;
+    }
+
+  if ((ret = pthread_join (t, &thr_ret)) != 0)
+    {
+      printf ("pthread_create failed: %s\n", strerror (ret));
+      return 1;
+    }
+
+  if (thr_ret != NULL)
+    return 1;
+
+  /* Now this should unload the DSO.  */
+  dlclose (handle);
+
+  /* Run through our maps and ensure that the DSO is unloaded.  */
+  FILE *f = fopen ("/proc/self/maps", "r");
+
+  if (f == NULL)
+    {
+      perror ("Failed to open /proc/self/maps");
+      fprintf (stderr, "Skipping verification of DSO unload\n");
+      return 0;
+    }
+
+  char *line = NULL;
+  size_t s = 0;
+  while (getline (&line, &s, f) > 0)
+    {
+      if (strstr (line, "tst-tls-atexit-lib.so"))
+        {
+	  printf ("DSO not unloaded yet:\n%s", line);
+	  return 1;
+	}
+    }
+  free (line);
+
+  return 0;
+}