Test various forms of threads tracking across exec(2).

diff --git a/gdb/testsuite/gdb.threads/threaded-exec.c b/gdb/testsuite/gdb.threads/threaded-exec.c
--- a/gdb/testsuite/gdb.threads/threaded-exec.c
+++ b/gdb/testsuite/gdb.threads/threaded-exec.c
@@ -18,21 +18,95 @@
    Boston, MA 02111-1307, USA.  */
 
 #include <stddef.h>
-#include <pthread.h>
 #include <assert.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <stdio.h>
 
+#ifdef THREADS
+
+# include <pthread.h>
 
 static void *
 threader (void *arg)
 {
-	return NULL;
+  return NULL;
 }
 
+#endif
+
 int
-main (void)
+main (int argc, char **argv)
 {
+  char *exec_nothreads, *exec_threads, *cmd;
+  int phase;
+  char phase_s[8];
+
+  setbuf (stdout, NULL);
+
+  if (argc != 4)
+    {
+      fprintf (stderr, "%s <non-threaded> <threaded> <phase>\n", argv[0]);
+      return 1;
+    }
+
+#ifdef THREADS
+  puts ("THREADS: Y");
+#else
+  puts ("THREADS: N");
+#endif
+  exec_nothreads = argv[1];
+  printf ("exec_nothreads: %s\n", exec_nothreads);
+  exec_threads = argv[2];
+  printf ("exec_threads: %s\n", exec_threads);
+  phase = atoi (argv[3]);
+  printf ("phase: %d\n", phase);
+
+  /* Phases: threading
+     0: N -> N
+     1: N -> Y
+     2: Y -> Y
+     3: Y -> N
+     4: N -> exit  */
+
+  cmd = NULL;
+
+#ifndef THREADS
+  switch (phase)
+    {
+    case 0:
+      cmd = exec_nothreads;
+      break;
+    case 1:
+      cmd = exec_threads;
+      break;
+    case 2:
+      fprintf (stderr, "%s: We should have threads for phase %d!\n", argv[0],
+	       phase);
+      return 1;
+    case 3:
+      fprintf (stderr, "%s: We should have threads for phase %d!\n", argv[0],
+	       phase);
+      return 1;
+    case 4:
+      return 0;
+    default:
+      assert (0);
+    }
+#else	/* THREADS */
+  switch (phase)
+    {
+    case 0:
+      fprintf (stderr, "%s: We should not have threads for phase %d!\n",
+	       argv[0], phase);
+      return 1;
+    case 1:
+      fprintf (stderr, "%s: We should not have threads for phase %d!\n",
+	       argv[0], phase);
+      return 1;
+    case 2:
+      cmd = exec_threads;
+      {
 	pthread_t t1;
 	int i;
 
@@ -40,7 +114,34 @@ main (void)
 	assert (i == 0);
 	i = pthread_join (t1, NULL);
 	assert (i == 0);
+      }
+      break;
+    case 3:
+      cmd = exec_nothreads;
+      {
+	pthread_t t1;
+	int i;
+
+	i = pthread_create (&t1, NULL, threader, (void *) NULL);
+	assert (i == 0);
+	i = pthread_join (t1, NULL);
+	assert (i == 0);
+      }
+      break;
+    case 4:
+      fprintf (stderr, "%s: We should not have threads for phase %d!\n",
+	       argv[0], phase);
+      return 1;
+    default:
+      assert (0);
+    }
+#endif	/* THREADS */
+
+  assert (cmd != NULL);
+
+  phase++;
+  snprintf (phase_s, sizeof phase_s, "%d", phase);
 
-	execl ("/bin/true", "/bin/true", NULL);
-	abort ();
+  execl (cmd, cmd, exec_nothreads, exec_threads, phase_s, NULL);
+  assert (0);
 }
diff --git a/gdb/testsuite/gdb.threads/threaded-exec.exp b/gdb/testsuite/gdb.threads/threaded-exec.exp
--- a/gdb/testsuite/gdb.threads/threaded-exec.exp
+++ b/gdb/testsuite/gdb.threads/threaded-exec.exp
@@ -20,9 +20,14 @@
 
 set testfile threaded-exec
 set srcfile ${testfile}.c
-set binfile [standard_output_file ${testfile}]
+set binfile_nothreads [standard_output_file ${testfile}N]
+set binfile_threads [standard_output_file ${testfile}Y]
 
-if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable []] != "" } {
+if {[gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile_nothreads}" executable {additional_flags=-UTHREADS}] != "" } {
+    return -1
+}
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile_threads}" executable {additional_flags=-DTHREADS}] != "" } {
     return -1
 }
 
@@ -30,9 +35,9 @@ gdb_exit
 gdb_start
 gdb_reinitialize_dir $srcdir/$subdir
 
-gdb_load ${binfile}
+gdb_load ${binfile_nothreads}
 
-gdb_run_cmd
+gdb_run_cmd ${binfile_nothreads} ${binfile_threads} 0
 
 gdb_test_multiple {} "Program exited" {
    -re "\r\n\\\[Inferior .* exited normally\\\]\r\n$gdb_prompt $" {

