[2.6 patch] compile with -ffreestanding

[2.6 patch] compile with -ffreestanding

[Adrian Bunk]

Hi Andrew,

for the kernel, it would be logical to use -ffreestanding. The kernel is 
not a hosted environment with a standard C library.

The gcc option -ffreestanding is supported by both gcc 2.95 and 3.4, 
which covers the whole range of currently supported compilers.

I'm currently running a 2.6.10-rc2-mm4 with this patch applied and 
compiled with gcc 2.95 and haven't yet observed any problems.

Regarding changes caused by this patch:

Andi Kleen reported:
  Newer gcc rewrites sprintf(buf,"%s",str) to strcpy(buf,str) transparently.

This is only true with unit-at-a-time (disabled on i386 but enabled
on x86_64). The Linux kernel doesn't offer a standard C library, and
such transparent replacements of kernel functions with builtins are
quite fragile.

Even with -ffreestanding, it's still possilble to explicitely use a gcc
builtin if desired.

Could you add the patch below to the next -mm to see whether there are 
any problems I didn't find?

TIA
Adrian



Signed-off-by: Adrian Bunk <bunk@stusta.de>

--- linux-2.6.10-rc1-mm4-full-ffreestanding/Makefile.old	2004-11-09 22:27:06.000000000 +0100
+++ linux-2.6.10-rc1-mm4-full-ffreestanding/Makefile	2004-11-09 22:27:47.000000000 +0100
@@ -349,7 +349,8 @@
 CPPFLAGS        := -D__KERNEL__ $(LINUXINCLUDE)
 
 CFLAGS 		:= -Wall -Wstrict-prototypes -Wno-trigraphs \
-	  	   -fno-strict-aliasing -fno-common
+	  	   -fno-strict-aliasing -fno-common \
+		   -ffreestanding
 AFLAGS		:= -D__ASSEMBLY__
 
 export	VERSION PATCHLEVEL SUBLEVEL EXTRAVERSION LOCALVERSION KERNELRELEASE \