Re: [PATCH] Guard against frame.c destructors running before frame-info.c's

["Kévin Le Gouguec" <legouguec@adacore.com>]

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Simon Marchi <simon.marchi@polymtl.ca> writes:

> Thanks, this reproduces for me too.  The patch looks good to me:
>
> Approved-By: Simon Marchi <simon.marchi@efficios.com>

Thanks!  Trailer appended in the attached.

I think I'll need help to install this; it's my first patch for GDB
AFAIR, so I don't believe I have push rights yet.


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From af4c192fd2d598836aa208d88035aa0dab5aa89e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?K=C3=A9vin=20Le=20Gouguec?= <legouguec@adacore.com>
Date: Tue, 15 Nov 2022 16:08:04 +0100
Subject: [PATCH] Guard against frame.c destructors running before
 frame-info.c's

On x86_64-windows, since 04e2ac7b2a7, we observe this internal error:

  [...]/gdbsupport/intrusive_list.h:458: internal-error: erase_element:
  Assertion `elem_node->prev != INTRUSIVE_LIST_UNLINKED_VALUE' failed.

Breaking in the destructors for intrusive_list and frame_info_ptr shows that
in this configuration, the destructors for frame.c's statically-stored
objects are run before frame-info.c's:

  Thread 1 hit Breakpoint 7, intrusive_list<frame_info_ptr,
  intrusive_base_node<frame_info_ptr> >::~intrusive_list (this=0x7ff69c418c90
  <frame_info_ptr::frame_list>, __in_chrg=<optimized out>)
  [...]/../gdbsupport/intrusive_list.h:250
  250	    clear ();
  (gdb) bt
  #0  intrusive_list<frame_info_ptr, intrusive_base_node<frame_info_ptr> >
      ::~intrusive_list (this=0x7ff69c418c90 <frame_info_ptr::frame_list>,
      __in_chrg=<optimized out>) [...]/../gdbsupport/intrusive_list.h:250
  #1  0x00007ff69b78edba in __tcf_1 () [...]/frame-info.c:27
  #2  0x00007ff9c457aa9f in msvcrt!_initterm_e ()
      from C:\Windows\System32\msvcrt.dll
  #3  0x00007ff69b8246a6 in captured_main_1 (context=0x5ffe00)
      [...]/main.c:1111
  #4  0x00007ff69b825149 in captured_main (data=0x5ffe00) [...]/main.c:1320
  #5  0x00007ff69b8251b1 in gdb_main (args=0x5ffe00) [...]/main.c:1345
  #6  0x00007ff69b5d1730 in main (argc=2, argv=0x751730) [...]/gdb.c:32
  (gdb) c
  Continuing.

  Thread 1 hit Breakpoint 8, frame_info_ptr::~frame_info_ptr
  (this=0x7ff69c418e20 <selected_frame>, __in_chrg=<optimized out>)
  [...]/frame-info.h:74
  74	    if (is_linked ())
  (gdb) bt
  #0  frame_info_ptr::~frame_info_ptr (this=0x7ff69c418e20 <selected_frame>,
      __in_chrg=<optimized out>) [...]/frame-info.h:74
  #1  0x00007ff69b79a643 in __tcf_1 () [...]/frame.c:1675
  #2  0x00007ff9c457aa9f in msvcrt!_initterm_e () from
      C:\Windows\System32\msvcrt.dll
  #3  0x00007ff69b8246a6 in captured_main_1 (context=0x5ffe00)
      [...]/main.c:1111
  #4  0x00007ff69b825149 in captured_main (data=0x5ffe00) [...]/main.c:1320
  #5  0x00007ff69b8251b1 in gdb_main (args=0x5ffe00) [...]/main.c:1345
  #6  0x00007ff69b5d1730 in main (argc=2, argv=0x751730) [...]/gdb.c:32

Approved-By: Simon Marchi <simon.marchi@efficios.com>
---
 gdb/frame-info.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/gdb/frame-info.h b/gdb/frame-info.h
index 3369b114326..893b6632363 100644
--- a/gdb/frame-info.h
+++ b/gdb/frame-info.h
@@ -76,7 +76,11 @@ class frame_info_ptr : public intrusive_list_node<frame_info_ptr>
 
   ~frame_info_ptr ()
   {
-    frame_list.erase (frame_list.iterator_to (*this));
+    /* If this node has static storage, it may be deleted after
+       frame_list.  Attempting to erase ourselves would then trigger
+       internal errors, so make sure we are still linked first.  */
+    if (is_linked ())
+      frame_list.erase (frame_list.iterator_to (*this));
   }
 
   frame_info_ptr &operator= (const frame_info_ptr &other)
-- 
2.25.1