Re: [bug #17647] glibc: GCC 4.1

[Thomas Schwinge <tschwinge at gnu dot org>]

Hello!

On Sun, Nov 26, 2006 at 11:27:58PM +0100, I wrote:
> The patch for glibc follows:

Here is an updated version, ready for inclusion as far as I'm concerned.


2007-07-22  Thomas Schwinge  <tschwinge@gnu.org>

	* sysdeps/mach/hurd/i386/init-first.c: Undo parts of Roland's `r 1.43'
	to `r 1.44' changes.
	(_hurd_stack_setup): Take a ``void *'' argument.  Save the caller into
	CALLER and pass that one on.
	(init): Avoid an ugly typecast.


Revert Roland patch.  (Part of `r 1.44' to 'r 1.43').

#v+
Index: sysdeps/mach/hurd/i386/init-first.c
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/mach/hurd/i386/init-first.c,v
retrieving revision 1.43.4.1
diff -u -p -r1.43.4.1 init-first.c
--- sysdeps/mach/hurd/i386/init-first.c	23 Oct 2005 01:00:09 -0000	1.43.4.1
+++ sysdeps/mach/hurd/i386/init-first.c	20 Nov 2006 11:05:47 -0000
@@ -320,11 +320,11 @@ first_init (void)
    stack set up just as the user will see it, so it can switch stacks.  */
 
 void
-_dl_init_first (void)
+_dl_init_first (int argc, ...)
 {
   first_init ();
 
-  init ((int *) __builtin_frame_address (0) + 2);
+  init (&argc);
 }
 #endif
 
@@ -351,23 +351,21 @@ strong_alias (posixland_init, __libc_ini
    This poorly-named function is called by static-start.S,
    which should not exist at all.  */
 void
-_hurd_stack_setup (void)
+_hurd_stack_setup (volatile int argc, ...)
 {
-  intptr_t caller = (intptr_t) __builtin_return_address (0);
-
   void doinit (intptr_t *data)
     {
       /* This function gets called with the argument data at TOS.  */
-      void doinit1 (void)
+      void doinit1 (volatile int argc, ...)
 	{
-	  init ((int *) __builtin_frame_address (0) + 2);
+	  init ((int *) &argc);
 	}
 
       /* Push the user return address after the argument data, and then
          jump to `doinit1' (above), so it is as if __libc_init_first's
          caller had called `doinit1' with the argument data already on the
          stack.  */
-      *--data = caller;
+      *--data = (&argc)[-1];
       asm volatile ("movl %0, %%esp\n" /* Switch to new outermost stack.  */
 		    "movl $0, %%ebp\n" /* Clear outermost frame pointer.  */
 		    "jmp *%1" : : "r" (data), "r" (&doinit1) : "sp");
@@ -376,7 +374,7 @@ _hurd_stack_setup (void)
 
   first_init ();
 
-  _hurd_startup ((void **) __builtin_frame_address (0) + 2, &doinit);
+  _hurd_startup ((void **) &argc, &doinit);
 }
 #endif
#v-


Make the code work with GCC 4.1.  This is essentially what Roland had done --
moving the resolution of the return address out of the nested subfunction --
but this time without replacing it with `__builtin_return_address'.

#v+
--- sysdeps/mach/hurd/i386/init-first.c	2007-07-22 16:50:03.000000000 +0200
+++ sysdeps/mach/hurd/i386/init-first.c	2007-07-22 18:33:45.540000000 +0200
@@ -350,8 +351,10 @@
    This poorly-named function is called by static-start.S,
    which should not exist at all.  */
 void
-_hurd_stack_setup (volatile int argc, ...)
+_hurd_stack_setup (void *arg, ...)
 {
+  void *caller = (&arg)[-1];
+
   void doinit (intptr_t *data)
     {
       /* This function gets called with the argument data at TOS.  */
@@ -364,7 +367,7 @@
          jump to `doinit1' (above), so it is as if __libc_init_first's
          caller had called `doinit1' with the argument data already on the
          stack.  */
-      *--data = (&argc)[-1];
+      *--data = (intptr_t) caller;
       asm volatile ("movl %0, %%esp\n" /* Switch to new outermost stack.  */
 		    "movl $0, %%ebp\n" /* Clear outermost frame pointer.  */
 		    "jmp *%1" : : "r" (data), "r" (&doinit1) : "sp");
@@ -373,7 +376,7 @@
 
   first_init ();
 
-  _hurd_startup ((void **) &argc, &doinit);
+  _hurd_startup (&arg, &doinit);
 }
 #endif
 
#v-


Cosmetical and documentation fixes.

#v+
Index: sysdeps/mach/hurd/i386/init-first.c
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/mach/hurd/i386/init-first.c,v
retrieving revision 1.43.4.1
diff -u -p -r1.43.4.1 init-first.c
--- sysdeps/mach/hurd/i386/init-first.c	23 Oct 2005 01:00:09 -0000	1.43.4.1
+++ sysdeps/mach/hurd/i386/init-first.c	20 Nov 2006 11:05:47 -0000
@@ -1,6 +1,7 @@
 /* Initialization code run first thing by the ELF startup code.  For i386/Hurd.
-   Copyright (C) 1995,96,97,98,99,2000,01,02,03,04,05
-	Free Software Foundation, Inc.
+   Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
+	2005, 2007 Free Software Foundation, Inc.
+
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -243,8 +243,8 @@ init (int *data)
 	 be the return address for `init1'; we will jump there with NEWSP
 	 as the stack pointer.  */
       *--newsp = data[-1];
-      ((void **) data)[-1] = switch_stacks;
-      /* Force NEWSP into %ecx and &init1 into %eax, which are not restored
+      data[-1] = (int) &switch_stacks;
+      /* Force NEWSP into %eax and &init1 into %ecx, which are not restored
 	 by function return.  */
       asm volatile ("# a %0 c %1" : : "a" (newsp), "c" (&init1));
     }
#v-


Regards,
 Thomas

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