[patch] Use malloc and free in atexit only when available. (Take 2)

[Jeff Johnston]

Patch checked in with small modification.  REENT_SMALL must always 
allocate the first atexit table
so there shouldn't be checking for _ATEXIT_DYNAMIC_ALLOC in that case 
(atexit table is null).

-- Jeff J.

Kazu Hirata wrote:
> Hi,
>
> Attached is a revised patch to use malloc and free in the support
> functions for atexit only when available.
>
> The previous version of this patch was posted at:
>
>   http://sourceware.org/ml/newlib/2009/msg00011.html
>
> In this iteration, I am leaving _ATEXIT_DYNAMIC_ALLOC mostly as is.
>
> There is one place where I forgot to guard a call to malloc with
> _ATEXIT_DYNAMIC_ALLOC in __atexit.c, so I am fixing that.
>
> This patch doesn't do the "if (!_ATEXIT_DYNAMIC_ALLOC ...)" trick
> anymore.  This way, I can ensure that --disable-atexit-dynamic-alloc
> really disables dynamic allocation even if the compiler does not
> optimize away dead code containing calls to malloc and/or free.
>
> Tested on fido-none-elf.  OK to apply?
>
> Kazu Hirata
>
> 2009-04-22  Paul Brook  <paul@codesourcery.com>
> 	    Kazu Hirata  <kazu@codesourcery.com>
>
> 	* libc/stdlib/__atexit.c (__register_exitproc): Use weak reference
> 	to malloc.  Allocate dynamically only if it is present.
> 	* libc/stdlib/__call_atexit.c (__call_exitprocs): Use weak
> 	reference to free.  Call free only if it is present.
>
> Index: newlib/libc/stdlib/__atexit.c
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdlib/__atexit.c,v
> retrieving revision 1.4
> diff -u -d -p -r1.4 __atexit.c
> --- newlib/libc/stdlib/__atexit.c	21 Mar 2006 00:57:34 -0000	1.4
> +++ newlib/libc/stdlib/__atexit.c	22 Apr 2009 04:40:00 -0000
> @@ -8,6 +8,8 @@
>  #include <sys/lock.h>
>  #include "atexit.h"
>  
> +/* Make this a weak reference to avoid pulling in malloc.  */
> +void * malloc(size_t) _ATTRIBUTE((__weak__));
>  
>  /*
>   * Register a function to be performed at exit or on shared library unload.
> @@ -38,6 +40,11 @@ _DEFUN (__register_exitproc,
>  #ifndef _ATEXIT_DYNAMIC_ALLOC
>        return -1;
>  #else
> +      /* Don't dynamically allocate the atexit array if malloc is not
> +	 available.  */
> +      if (!malloc)
> +	return -1;
> +
>        p = (struct _atexit *) malloc (sizeof *p);
>        if (p == NULL)
>  	{
> @@ -62,7 +69,11 @@ _DEFUN (__register_exitproc,
>        args = p->_on_exit_args_ptr;
>        if (args == NULL)
>  	{
> -	  args = malloc (sizeof * p->_on_exit_args_ptr);
> +#ifdef _ATEXIT_DYNAMIC_ALLOC
> +	  if (malloc)
> +	    args = malloc (sizeof * p->_on_exit_args_ptr);
> +#endif
> +
>  	  if (args == NULL)
>  	    {
>  #ifndef __SINGLE_THREAD__
> Index: newlib/libc/stdlib/__call_atexit.c
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdlib/__call_atexit.c,v
> retrieving revision 1.5
> diff -u -d -p -r1.5 __call_atexit.c
> --- newlib/libc/stdlib/__call_atexit.c	5 Apr 2007 16:47:38 -0000	1.5
> +++ newlib/libc/stdlib/__call_atexit.c	22 Apr 2009 04:40:00 -0000
> @@ -7,6 +7,9 @@
>  #include <reent.h>
>  #include "atexit.h"
>  
> +/* Make this a weak reference to avoid pulling in free.  */
> +void free(void *) _ATTRIBUTE((__weak__));
> +
>  /*
>   * Call registered exit handlers.  If D is null then all handlers are called,
>   * otherwise only the handlers from that DSO are called.
> @@ -76,6 +79,11 @@ _DEFUN (__call_exitprocs, (code, d),
>  #ifndef _ATEXIT_DYNAMIC_ALLOC
>        break;
>  #else
> +      /* Don't dynamically free the atexit array if free is not
> +	 available.  */
> +      if (!free)
> +	break;
> +
>        /* Move to the next block.  Free empty blocks except the last one,
>  	 which is part of _GLOBAL_REENT.  */
>        if (p->_ind == 0 && p->_next)
>