[binutils-gdb] [gdb/build] Workaround gcc PR113599

[binutils-gdb] [gdb/build] Workaround gcc PR113599

[Tom de Vries]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2ec7980408fafb172d2ddb716a367ce2111e2e9e

commit 2ec7980408fafb172d2ddb716a367ce2111e2e9e
Author: Tom de Vries <tdevries@suse.de>
Date:   Thu Jan 25 16:31:47 2024 +0100

    [gdb/build] Workaround gcc PR113599
    
    Since gcc commit d3f48f68227 ("c++: non-dependent .* operand folding
    [PR112427]"), with gdb we run into PR gcc/113599 [1], a wrong-code bug, as
    reported in PR build/31281.
    
    Work around this by flipping inherit order:
    ...
    -class thread_info : public refcounted_object,
    -                   public intrusive_list_node<thread_info>
    +class thread_info : public intrusive_list_node<thread_info>,
    +                   public refcounted_object
    ...
    
    An argument could be made that this isn't necessary, because this occurred in
    an unreleased gcc version.
    
    However, I think it could be useful when bisecting gcc for other problems in
    building gdb.  Having this workaround means the bisect won't reintroduce the
    problem.  Furthermore, the workaround is harmless.
    
    Tested on Fedora rawhide x86_64.
    
    Approved-By: Tom Tromey <tom@tromey.com>
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31281
    
    [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113599

Diff:
---
 gdb/gdbthread.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h
index e7035d40ad4..11c553a99ca 100644
--- a/gdb/gdbthread.h
+++ b/gdb/gdbthread.h
@@ -244,10 +244,11 @@ using private_thread_info_up = std::unique_ptr<private_thread_info>;
    strong reference, and is thus not accounted for in the thread's
    refcount.
 
-   The intrusive_list_node base links threads in a per-inferior list.  */
+   The intrusive_list_node base links threads in a per-inferior list.
+   We place it first in the inherit order to work around PR gcc/113599.  */
 
-class thread_info : public refcounted_object,
-		    public intrusive_list_node<thread_info>
+class thread_info : public intrusive_list_node<thread_info>,
+		    public refcounted_object
 {
 public:
   explicit thread_info (inferior *inf, ptid_t ptid);