User level Macros for Endianess

[David A. Gatwood]

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out-of-date) architectures that are neither big nor little.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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