Eric Noulard wrote:
May be you could use TRY_RUN to detect endianity
with something like:
TRY_RUN(
ENDIANESS_RESULT
ENDIANESS_COMPILE
/tmp/
${CMAKE_CURRENT_SOURCE_DIR}/make/endianess.c
OUTPUT_VARIABLE ENDIANESS_OUT
)
MESSAGE(STATUS "ENDIANITY is :${ENDIANESS_OUT}")
endianess.c is attached.
The trouble I have is that I expected to have
my "endianess" program output in ${ENDIANESS_OUT}
but I get too much including
compilation process ouput.
The format is:
TRY_RUN(RUN_RESULT_VAR COMPILE_RESULT_VAR
bindir srcfile <CMAKE_FLAGS <Flags>>
<COMPILE_DEFINITIONS <flags>>
<OUTPUT_VARIABLE var>
<ARGS <arg1> <arg2>..
Write a test called IsBigEndian.c. When run, have it return either 0 or
1. Get the result with RUN_RESULT_VAR. Use it and be happy. Caveat: 0
is typically regarded as a *success* code when running a system tool, so
go over your bit twiddling convention carefully. I can't remember what
I did in Chicken's StackGrowsDownward.c, only that Felix caught me doing
it backwards and I was surprised.
Use COMPILER_RESULT_VAR to make sure your code actually worked, and
throw errors if it doesn't. Your code should always compile; this would
be a strange / severe / exceptional error.
OUTPUT_VARIABLE isn't useful for this kind of problem. It gives you all
the stdout stuff and you don't want that.
A complete working example of this kind of code is available in the
Chicken CMake build. Search CMakeLists.txt for STACK_GROWS_DOWNWARD.
http://www.call-with-current-continuation.org . I think I'll document
it more, so that the return code conventions are less confusing.
Cheers,
Brandon Van Every
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