[gcc r13-2801] Avoid depending on destructor order

[Thomas Neumann <tneumann@gcc.gnu.org>]

https://gcc.gnu.org/g:94ccaf62c378c3737f7e4b6a80e1160157119171

commit r13-2801-g94ccaf62c378c3737f7e4b6a80e1160157119171
Author: Thomas Neumann <tneumann@users.sourceforge.net>
Date:   Mon Sep 19 18:10:02 2022 +0200

    Avoid depending on destructor order
    
    In some scenarios (e.g., when mixing gcc and clang code), it can
    happen that frames are deregistered after the lookup structure
    has already been destroyed. That in itself would be fine, but
    it triggers an assert in __deregister_frame_info_bases that
    expects to find the frame.
    
    To avoid that, we now remember that the btree as already been
    destroyed and disable the assert in that case.
    
    libgcc/ChangeLog:
    
            * unwind-dw2-fde.c: (release_register_frames) Remember
            when the btree has been destroyed.
            (__deregister_frame_info_bases) Disable the assert when
            shutting down.

Diff:
---
 libgcc/unwind-dw2-fde.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
index 919abfe0664..d237179f4ea 100644
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -48,6 +48,7 @@ typedef __UINTPTR_TYPE__ uintptr_type;
 #include "unwind-dw2-btree.h"
 
 static struct btree registered_frames;
+static bool in_shutdown;
 
 static void
 release_registered_frames (void) __attribute__ ((destructor (110)));
@@ -57,6 +58,7 @@ release_registered_frames (void)
   /* Release the b-tree and all frames. Frame releases that happen later are
    * silently ignored */
   btree_destroy (&registered_frames);
+  in_shutdown = true;
 }
 
 static void
@@ -282,7 +284,7 @@ __deregister_frame_info_bases (const void *begin)
   __gthread_mutex_unlock (&object_mutex);
 #endif
 
-  gcc_assert (ob);
+  gcc_assert (in_shutdown || ob);
   return (void *) ob;
 }