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Re: [PATCH] MIPS: decompressor: fix build failure on memcpy() in decompr

To: ralf@linux-mips.org
Subject: Re: [PATCH] MIPS: decompressor: fix build failure on memcpy() in decompress.c
From: Florian Fainelli <florian@openwrt.org>
Date: Tue, 13 Nov 2012 12:25:15 +0100
Cc: linux-mips@linux-mips.org, blogic@openwrt.org, wuzhangjin@gmail.com
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On Monday 12 November 2012 12:46:58 Florian Fainelli wrote:
> The decompress.c file includes linux/kernel.h which causes the following
> inclusion chain to be pulled:
> linux/kernel.h ->
>       linux/dynamic_debug.h ->
>               linux/string.h ->
>                       asm/string.h
> 
> We end up having a the GCC builtin + architecture specific memcpy() expanding
> into this:
> 
> void *({ size_t __len = (size_t n); void *__ret; if
> (__builtin_constant_p(size_t n) && __len >= 64) __ret = memcpy((void *dest),
> (const void *src), __len); else __ret = __builtin_memcpy((void *dest), (const
> void *src), __len); __ret; })

After some more debugging, this expansion "failure" actually comes from one
of our OpenWrt patch which allows the use of GCC builtins for memcpy and
friends. The fix remains valid anyway.

> {
>  [memcpy implementation in decompress.c starts here]
>  int i;
>  const char *s = src;
>  char *d = dest;
> 
>  for (i = 0; i < n; i++)
>   d[i] = s[i];
>  return dest;
> }
> 
> raising the following compilation error:
> arch/mips/boot/compressed/decompress.c:46:8: error: expected identifier or '('
> before '{' token
> 
> There are at least three possibilities to fix this issue:
> 
> 1) define _LINUX_STRING_H_ at the beginning of decompress.c to prevent
>    further linux/string.h definitions and declarations from being used, and 
> add
>    an explicit strstr() declaration for linux/dynamic_debug.h
> 
> 2) remove the inclusion of linux/kernel.h because we actually use no 
> definition
>    or declaration from this header file
> 
> 3) undefine memcpy or re-define memcpy to memcpy thus resulting in picking up
>    the local memcpy() implementation to this compilation unit
> 
> This patch uses the second option which is the less intrusive one.
> 
> Signed-off-by: Florian Fainelli <florian@openwrt.org>
> ---
>  arch/mips/boot/compressed/decompress.c |    2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/mips/boot/compressed/decompress.c 
> b/arch/mips/boot/compressed/decompress.c
> index 5cad0fa..d6c5586 100644
> --- a/arch/mips/boot/compressed/decompress.c
> +++ b/arch/mips/boot/compressed/decompress.c
> @@ -10,9 +10,7 @@
>   * Free Software Foundation;  either version 2 of the  License, or (at your
>   * option) any later version.
>   */
> -
>  #include <linux/types.h>
> -#include <linux/kernel.h>
>  
>  #include <asm/addrspace.h>
>  
> -- 
> 1.7.10.4
> 

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