[PATCH] Avoid depending on destructor order

[Thomas Neumann <neumann@in.tum.de>]

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.
---
  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;
  }

-- 
2.34.1