[binutils-gdb] [gdb/build] Fix frame_list position in frame.c

[binutils-gdb] [gdb/build] Fix frame_list position in frame.c

[Tom de Vries]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=751c7c72c0105c7d55e58bba3c069c36a74c8937

commit 751c7c72c0105c7d55e58bba3c069c36a74c8937
Author: Tom de Vries <tdevries@suse.de>
Date:   Wed May 3 21:43:03 2023 +0200

    [gdb/build] Fix frame_list position in frame.c
    
    In commit 995a34b1772 ("Guard against frame.c destructors running before
    frame-info.c's") the following problem was addressed.
    
    The frame_info_ptr destructor:
    ...
      ~frame_info_ptr ()
      {
        frame_list.erase (frame_list.iterator_to (*this));
      }
    ...
    uses frame_list, which is a static member of class frame_info_ptr,
    instantiated in frame-info.c:
    ...
    intrusive_list<frame_info_ptr> frame_info_ptr::frame_list;
    ...
    
    Then there's a static frame_info_pointer variable named selected_frame in
    frame.c:
    ...
    static frame_info_ptr selected_frame;
    ...
    
    Because the destructor of selected_frame uses frame_list, its destructor needs
    to be called before the destructor of frame_list.
    
    But because they're in different compilation units, the initialization order and
    consequently destruction order is not guarantueed.
    
    The commit fixed this by handling the case that the destructor of frame_list
    is called first, adding a check on is_linked ():
    ...
       ~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));
       }
    ...
    
    However, since then frame_list has been moved into frame.c, and
    initialization/destruction order is guarantueed inside a compilation unit.
    
    Revert aforementioned commit, and fix the destruction order problem by moving
    frame_list before selected_frame.
    
    Reverting the commit is another way of fixing the already fixed
    Wdangling-pointer warning reported in PR build/30413, in a different way than
    commit 9b0ccb1ebae ("Pass const frame_info_ptr reference for
    skip_[language_]trampoline").
    
    Approved-By: Simon Marchi <simon.marchi@efficios.com>
    Tested on x86_64-linux.
    PR build/30413
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30413

Diff:
---
 gdb/frame.c | 11 +++++++----
 gdb/frame.h |  8 +++-----
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/gdb/frame.c b/gdb/frame.c
index 36fb02f3c8e..c8b8d2e257e 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -1733,6 +1733,13 @@ get_current_frame (void)
 static frame_id selected_frame_id = null_frame_id;
 static int selected_frame_level = -1;
 
+/* See frame.h.  This definition should come before any definition of a static
+   frame_info_ptr, to ensure that frame_list is destroyed after any static
+   frame_info_ptr.  This is necessary because the destructor of frame_info_ptr
+   uses frame_list.  */
+
+intrusive_list<frame_info_ptr> frame_info_ptr::frame_list;
+
 /* The cached frame_info object pointing to the selected frame.
    Looked up on demand by get_selected_frame.  */
 static frame_info_ptr selected_frame;
@@ -3275,10 +3282,6 @@ maintenance_print_frame_id (const char *args, int from_tty)
 
 /* See frame-info-ptr.h.  */
 
-intrusive_list<frame_info_ptr> frame_info_ptr::frame_list;
-
-/* See frame-info-ptr.h.  */
-
 frame_info_ptr::frame_info_ptr (struct frame_info *ptr)
   : m_ptr (ptr)
 {
diff --git a/gdb/frame.h b/gdb/frame.h
index 6ed8db0af56..355150ab585 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -254,11 +254,9 @@ public:
 
   ~frame_info_ptr ()
   {
-    /* 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));
+    /* If this node has static storage, it should be be deleted before
+       frame_list.  */
+    frame_list.erase (frame_list.iterator_to (*this));
   }
 
   frame_info_ptr &operator= (const frame_info_ptr &other)