http://sourceware.org/ml/gdb-patches/2011-02/msg00680.html
Subject: [patch 2/3] Fix threading internal error on corrupted memory [rediff]

[rediff]

gdb/
2011-02-24  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* linux-thread-db.c (find_new_threads_callback): Exit on zero TI_TID
	even if !TARGET_HAS_EXECUTION.

gdb/testsuite/
2011-02-24  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.threads/gcore-thread.exp ($core0file): New variable.
	(clear __stack_user.next, clear stack_used.next)
	(save a zeroed-threads corefile): New test.
	Call core_load for $core0file.
	(zeroed-threads cannot be listed): New test.

--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -1335,7 +1335,7 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
   if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE)
     return 0;			/* A zombie -- ignore.  */
 
-  if (ti.ti_tid == 0 && target_has_execution)
+  if (ti.ti_tid == 0)
     {
       /* A thread ID of zero means that this is the main thread, but
 	 glibc has not yet initialized thread-local storage and the
@@ -1347,10 +1347,13 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
 	 need this glibc bug workaround.  */
       info->need_stale_parent_threads_check = 0;
 
-      err = info->td_thr_event_enable_p (th_p, 1);
-      if (err != TD_OK)
-	error (_("Cannot enable thread event reporting for LWP %d: %s"),
-	       (int) ti.ti_lid, thread_db_err_str (err));
+      if (target_has_execution)
+	{
+	  err = info->td_thr_event_enable_p (th_p, 1);
+	  if (err != TD_OK)
+	    error (_("Cannot enable thread event reporting for LWP %d: %s"),
+		   (int) ti.ti_lid, thread_db_err_str (err));
+	}
 
       return 0;
     }
--- a/gdb/testsuite/gdb.threads/gcore-thread.exp
+++ b/gdb/testsuite/gdb.threads/gcore-thread.exp
@@ -26,6 +26,7 @@ set testfile "gcore-thread"
 set srcfile  pthreads.c
 set binfile  ${objdir}/${subdir}/${testfile}
 set corefile ${objdir}/${subdir}/${testfile}.test
+set core0file ${objdir}/${subdir}/${testfile}0.test
 
 if [istarget "*-*-linux"] then {
     set target_cflags "-D_MIT_POSIX_THREADS"
@@ -110,6 +111,29 @@ if {!$core_supported} {
 }
 
 
+# Test the uninitialized thread list.
+# Provide the case of glibc td_thr_get_info handling of:
+# /* Special case for the main thread before initialization.  */
+
+foreach symbol {__stack_user stack_used} {
+    set test "clear ${symbol}.next"
+    gdb_test_multiple "p *(void **) &${symbol} = 0" $test {
+	-re " = \\(void \\*\\) 0x0\r\n$gdb_prompt $" {
+	    pass $test
+	}
+	-re "No symbol \"${symbol}\" in current context\\.\r\n$gdb_prompt $" {
+	    xfail $test
+	    # Do not do the verification.
+	    set core0file ""
+	}
+    }
+}
+
+if {"$core0file" != ""} {
+    gdb_test "gcore $core0file" "Saved corefile .*" "save a zeroed-threads corefile"
+}
+
+
 # Now restart gdb and load the corefile.
 clean_restart ${testfile}
 
@@ -160,3 +184,11 @@ gdb_test "info threads" ".* thread2 .*" \
 
 gdb_test "info threads" ".*${nl}\\* ${horiz} thread2 .*" \
 	"thread2 is current thread in corefile"
+
+
+# Test the uninitialized thread list.
+
+if {"$core0file" != "" && [load_core $core0file]} {
+
+    gdb_test "info threads" "Cannot find new threads: .*" "zeroed-threads cannot be listed"
+}