User level Macros for Endianess
David A. Gatwood
dgatwood at deepspace.mklinux.org
Fri Jan 14 02:48:53 EST 2000
On Thu, 13 Jan 2000, Stephane GEORGES wrote:
> I use my own executable compiled by GNU before compiling anything else:
>
> bigendian.c
> -----------
>
> int main()
> {
> unsigned short val = 0x0011;
> unsigned char* str = (unsigned char*)&val;
> if ( str[0] == 0x00 )
> return 1;
> else
> return 0;
> }
>
> in my GNUmakefile
> -----------------
>
> - one rule to compile bigendian.c if exe not compiled
> - one rule testing the return value of exe and setting
>
> MEMORY_IS_LITTLE_ENDIAN or MEMORY_IS_BIG_ENDIAN
>
> That way I do not need to look for the right MACRO on the right SYSTEM.
>
> I compile my code on IRIX (SGI), Solaris (SUN), intel Linux and LinuxPPC.
One worry here is that there are a few obscure (and generally, pretty
out-of-date) architectures that are neither big nor little. Since this
only checks the first byte against the big value, it will return little
endian on a few oddball machines. Other than that, though, yes, that
should work.
David
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