Re: [Discuss-gnuradio] configure tests?

[Eric Blossom]

On Fri, May 26, 2006 at 03:58:42PM -0400, Michael Dickens wrote:
> I think I've got the issue with gr-audio-osx running on Intel  
> Macs ... it's about endianness in the float stream.  Which means, if  
> I'm correct, that I need to add a #ifdef to select on whether the CPU  
> is big (PPC) or little (Intel) endian.  Anyone know if this is  
> already available for configure, or will I need to add one?  If the  
> latter, I'm sure it's straight forward (e.g. `uname -a | grep  
> powerpc` == ""), but why reinvent the wheel?

There's already a test in the usrp and gr-usrp code for this.
See configure.ac, AC_C_BIGENDIAN.
See also usrp/host/lib/usrp_bytesex.h

I believe that the gr-usrp code already handles this properly.
See gr-usrp/usrp1_{sink,source}_{c,s}.cc.

Search for host_to_usrp_short and usrp_to_host_short


> Also, it looks like Apple's GCC implements the ".align X" in assembly  
> as a log2 based number (for either PPC or Intel) while others use  
> ".align Y" where X = log2 (Y) .. a linear number.  I really doubt  
> that this is available for configure, but it's worth checking.  I've  
> already started writing this one ("config/gr_asm_dot_align.m4"), but  
> again why reinvent the wheel?

I don't know of a test for this.
How are you planning on implementing the test? 
I'd suggest something like:

  in test.asm (syntax could be wrong...)

        .globl _start_test, _end_test

        .align  16
  _start_test:
        .db     1
        .align  4
  _end_test:


Then use nm to extract the resulting symbol values, followed by some
python, etc to compute difference.  Or I guess your test code could
just write the difference to stdout, then you could parse that.

Eric