gdb/gdb-stale-frame_info.patch

From 78ed78584876c1c7e2aada2f9614fabb34597325 Mon Sep 17 00:00:00 2001
From: Fedora GDB patches <invalid@email.com>
Date: Fri, 27 Oct 2017 21:07:50 +0200
Subject: workaround stale frame_info * (PR 13866)

FileName: gdb-stale-frame_info.patch

;; Workaround crashes from stale frame_info pointer (BZ 804256).
;;=push+jan

http://sourceware.org/ml/gdb-patches/2012-04/msg00058.html

Hi,

I did not look at which commit caused this regression but apparently it was
introduced at least with multi-inferiors.

I understand this fix is not right fix of the crash; but in most GDB cases one
does not use multi-inferior so why to regress single-inferior by it.
Some more simple solutions still fix the single-inferior mode but they
regressed the multi-inferior mode
	gdb.threads/no-unwaited-for-left.exp
	gdb.multi/base.exp
so I had to put there that sorting magic.

With proper C++ sanity check of stale live frame_info references the testcase
would be simple without the "frame_garbage_collection" reproducer below.
It is also reproducible just with valgrind but regularly running the whole
testsuite under valgrind I did not find feasible.

No regressions on {x86_64,x86_64-m32,i686}-fedora17-linux-gnu.

Thanks,
Jan

gdb/
2012-04-04  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Workaround PR backtrace/13866.
	* progspace.c (switch_to_program_space_and_thread): Try not to call
	switch_to_thread.
---
 gdb/progspace-and-thread.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/gdb/progspace-and-thread.c b/gdb/progspace-and-thread.c
index a48faa0f96..8446bfa336 100644
--- a/gdb/progspace-and-thread.c
+++ b/gdb/progspace-and-thread.c
@@ -23,15 +23,29 @@
 void
 switch_to_program_space_and_thread (program_space *pspace)
 {
-  inferior *inf = find_inferior_for_program_space (pspace);
+  inferior *inf = current_inferior ();
+
+  if (inf->pspace != pspace)
+    inf = find_inferior_for_program_space (pspace);
 
   if (inf != NULL && inf->pid != 0)
     {
       thread_info *tp = any_live_thread_of_process (inf->pid);
+      thread_info *current_tp = NULL;
+
+      if (ptid_get_pid (inferior_ptid) == inf->pid)
+	current_tp = find_thread_ptid (inferior_ptid);
 
       if (tp != NULL)
 	{
-	  switch_to_thread (tp->ptid);
+	  /* Prefer primarily thread not THREAD_EXITED and secondarily thread
+	     not EXECUTING.  */
+	  if (current_tp == NULL
+	      || (tp->state != THREAD_EXITED
+		  && current_tp->state == THREAD_EXITED)
+	      || (!tp->executing && current_tp->executing))
+	    switch_to_thread (tp->ptid);
+
 	  /* Switching thread switches pspace implicitly.  We're
 	     done.  */
 	  return;
-- 
2.14.3