Re: RFA: Recognize bottom of stack on Linux

[Jim Blandy <jimb@zwingli.cygnus.com>]

Daniel Jacobowitz <drow@mvista.com> writes:
> I like this.  The way func_frame_chain_valid should really be used is
> by something like:
> 
>   /* NOTE: tm-i386nw.h and tm-i386v4.h override this.  */
>   set_gdbarch_frame_chain_valid (gdbarch, file_frame_chain_valid);
> 
> (copied from i386-tdep.c).
> 
> Does this patch work for you?

Yes, thanks.  I've included a revised version of my patch below.

> I'm curious as to why we can't just set this universally, or at least a
> little more globally.  Most things that have a main () use it as a
> normal main ().  I'd propose that we set it as the default frame chain,
> and provide/document an option to ignore inside_main_func.

Well, gdbarch is never supposed to change the default behavior of
macros; this helps us convert pre-gdbarch targets incrementally.
Simply turning on gdbarch for one's target ideally wouldn't change its
behavior at all.


2002-02-06  Jim Blandy  <jimb@redhat.com>

	Fix from Daniel Jacobowitz:
	* config/i386/tm-linux.h (FRAME_CHAIN_VALID): Use
	`func_frame_chain_valid' for this.
	* i386-tdep.c (i386_gdbarch_init): Note that tm-linux.h is
	overriding the selection we make here.

Index: gdb/i386-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.c,v
retrieving revision 1.50
diff -c -r1.50 i386-tdep.c
*** gdb/i386-tdep.c	2002/01/01 16:29:43	1.50
--- gdb/i386-tdep.c	2002/02/06 19:19:27
***************
*** 1324,1330 ****
  
    set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_on_stack);
  
!   /* NOTE: tm-i386nw.h and tm-i386v4.h override this.  */
    set_gdbarch_frame_chain_valid (gdbarch, file_frame_chain_valid);
  
    /* NOTE: tm-i386aix.h, tm-i386bsd.h, tm-i386os9k.h, tm-linux.h,
--- 1324,1330 ----
  
    set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_on_stack);
  
!   /* NOTE: tm-i386nw.h, tm-i386v4.h, and tm-linux.h override this.  */
    set_gdbarch_frame_chain_valid (gdbarch, file_frame_chain_valid);
  
    /* NOTE: tm-i386aix.h, tm-i386bsd.h, tm-i386os9k.h, tm-linux.h,
Index: gdb/config/i386/tm-linux.h
===================================================================
RCS file: /cvs/src/src/gdb/config/i386/tm-linux.h,v
retrieving revision 1.16
diff -c -r1.16 tm-linux.h
*** gdb/config/i386/tm-linux.h	2001/11/08 00:03:52	1.16
--- gdb/config/i386/tm-linux.h	2002/02/06 19:19:28
***************
*** 82,87 ****
--- 82,98 ----
  #define IN_SIGTRAMP(pc, name) i386_linux_in_sigtramp (pc, name)
  extern int i386_linux_in_sigtramp (CORE_ADDR, char *);
  
+ /* On Linux, the entry point is called _start, but that invokes
+    something called __libc_start_main, which calls main.  So if we
+    want the stack to end at main (as it does for most GDB targets),
+    it's not enough for us to use inside_entry_func or
+    inside_entry_file; that rule will only trigger after we've included
+    __libc_start_main in the backtrace, which we don't want.
+    func_frame_chain_valid checks both for `main', and for the entry
+    point function.  */
+ /* Use the alternate method of determining valid frame chains. */
+ #define FRAME_CHAIN_VALID(fp,fi) func_frame_chain_valid (fp, fi)
+ 
  #undef FRAME_CHAIN
  #define FRAME_CHAIN(frame) i386_linux_frame_chain (frame)
  extern CORE_ADDR i386_linux_frame_chain (struct frame_info *frame);