[CMake] Finding out the Endianness of a system at CMake config time

[Brandon J. Van Every]

Mike Jackson wrote:
> I have recently joined a project where I am to do some coding. The 
> code base is cross platform HPC type code and the original coders have 
> defined their own little/big endian #defines (L_ENDIAN & B_ENDIAN). 
> They pass this into the compiler via -DL_ENDIAN during compiles. 
>
> Is there a way to automatically have cmake figure this out for me? 
> Right now I have an OPTION(....) clause in my CMakeLists.txt file to 
> select the right value.. which is stupid and error prone but it worked 
> to boot strap the process for the moment.
>
> Any hints would be appreciated.. 

You could do a TRY_COMPILE with a snippet of C code that tests for 
endinanness.  I always forget how to write such a snippet off the top of 
my head.  I typically look at an Autoconf ./configure script to see what 
they did, or Google around for it.  The Chicken Scheme CMake build has 
an example of detecting whether the stack grows downward, in 
StackGrowsDownward.c.


Cheers,
Brandon Van Every

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