[PATCH] Pass const frame_info_ptr reference for skip_[language_]trampoline

[Mark Wielaard <mark@klomp.org>]

g++ 13.1.1 produces a -Werror=dangling-pointer=

In file included from ../../binutils-gdb/gdb/frame.h:75,
                 from ../../binutils-gdb/gdb/symtab.h:40,
                 from ../../binutils-gdb/gdb/language.c:33:
In member function ‘void intrusive_list<T, AsNode>::push_empty(T&) [with T = frame_info_ptr; AsNode = intrusive_base_node<frame_info_ptr>]’,
    inlined from ‘void intrusive_list<T, AsNode>::push_back(reference) [with T = frame_info_ptr; AsNode = intrusive_base_node<frame_info_ptr>]’ at gdbsupport/intrusive_list.h:332:24,
    inlined from ‘frame_info_ptr::frame_info_ptr(const frame_info_ptr&)’ at gdb/frame.h:241:26,
    inlined from ‘CORE_ADDR skip_language_trampoline(frame_info_ptr, CORE_ADDR)’ at gdb/language.c:530:49:
gdbsupport/intrusive_list.h:415:12: error: storing the address of local variable ‘<anonymous>’ in ‘frame_info_ptr::frame_list.intrusive_list<frame_info_ptr>::m_back’ [-Werror=dangling-pointer=]
  415 |     m_back = &elem;
      |     ~~~~~~~^~~~~~~
gdb/language.c: In function ‘CORE_ADDR skip_language_trampoline(frame_info_ptr, CORE_ADDR)’:
gdb/language.c:530:49: note: ‘<anonymous>’ declared here
  530 |       CORE_ADDR real_pc = lang->skip_trampoline (frame, pc);
      |                           ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
gdb/frame.h:359:41: note: ‘frame_info_ptr::frame_list’ declared here
  359 |   static intrusive_list<frame_info_ptr> frame_list;
      |                                         ^~~~~~~~~~

Each new frame_info_ptr is being pushed on a static frame list and g++
cannot see why that is safe in case the frame_info_ptr is created and
destroyed immediately when passed as value.

It isn't clear why only in this one place g++ sees the issue (probably
because it can inlined enough code in this specific case).

Since passing the frame_info_ptr as const reference is cheaper, use
that as workaround for this warning.
---
 gdb/c-lang.c    | 2 +-
 gdb/language.c  | 2 +-
 gdb/language.h  | 4 ++--
 gdb/objc-lang.c | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/gdb/c-lang.c b/gdb/c-lang.c
index 6535ab93498..484f81e455b 100644
--- a/gdb/c-lang.c
+++ b/gdb/c-lang.c
@@ -1002,7 +1002,7 @@ class cplus_language : public language_defn
 
   /* See language.h.  */
 
-  CORE_ADDR skip_trampoline (frame_info_ptr fi,
+  CORE_ADDR skip_trampoline (const frame_info_ptr &fi,
 			     CORE_ADDR pc) const override
   {
     return cplus_skip_trampoline (fi, pc);
diff --git a/gdb/language.c b/gdb/language.c
index 0b4202ff839..f82c5b173b3 100644
--- a/gdb/language.c
+++ b/gdb/language.c
@@ -523,7 +523,7 @@ add_set_language_command ()
    Return the result from the first that returns non-zero, or 0 if all
    `fail'.  */
 CORE_ADDR 
-skip_language_trampoline (frame_info_ptr frame, CORE_ADDR pc)
+skip_language_trampoline (const frame_info_ptr &frame, CORE_ADDR pc)
 {
   for (const auto &lang : language_defn::languages)
     {
diff --git a/gdb/language.h b/gdb/language.h
index 4c91776d94d..0ebd4c1d957 100644
--- a/gdb/language.h
+++ b/gdb/language.h
@@ -471,7 +471,7 @@ struct language_defn
      If that PC falls in a trampoline belonging to this language, return
      the address of the first pc in the real function, or 0 if it isn't a
      language tramp for this language.  */
-  virtual CORE_ADDR skip_trampoline (frame_info_ptr fi, CORE_ADDR pc) const
+  virtual CORE_ADDR skip_trampoline (const frame_info_ptr &fi, CORE_ADDR pc) const
   {
     return (CORE_ADDR) 0;
   }
@@ -790,7 +790,7 @@ extern const char *language_str (enum language);
 
 /* Check for a language-specific trampoline.  */
 
-extern CORE_ADDR skip_language_trampoline (frame_info_ptr, CORE_ADDR pc);
+extern CORE_ADDR skip_language_trampoline (const frame_info_ptr &, CORE_ADDR pc);
 
 /* Return information about whether TYPE should be passed
    (and returned) by reference at the language level.  */
diff --git a/gdb/objc-lang.c b/gdb/objc-lang.c
index ccbe7c19729..6af25d9c988 100644
--- a/gdb/objc-lang.c
+++ b/gdb/objc-lang.c
@@ -282,7 +282,7 @@ class objc_language : public language_defn
 
   /* See language.h.  */
 
-  CORE_ADDR skip_trampoline (frame_info_ptr frame,
+  CORE_ADDR skip_trampoline (const frame_info_ptr &frame,
 			     CORE_ADDR stop_pc) const override
   {
     struct gdbarch *gdbarch = get_frame_arch (frame);
-- 
2.31.1