[CMake] TRY_COMPILE painful for tool testing

[Brandon J. Van Every]

Brandon J. Van Every wrote:
> William A. Hoffman wrote:
>> At 08:17 AM 7/22/2006, Brad King wrote:
>>   
>>> Brandon J. Van Every wrote:
>>>     
>>>> Ok, the CMake 2.4.2 documentation for the projectName version of TRY_COMPILE is only 3 short sentences.  IIUYC, you are saying I'm going to have to write a CMakeLists.txt wrapper, and a subdirectory, for each and every tool like "makeinfo," if I want to prove that they work in the build.
>>>>       
>>> You can create a macro to wrap this all up.  The source tree for the TRY_COMPILE can be created with FILE(WRITE) and FILE(MAKE_DIRECTORY).
>>>     
>> Regardless of the documentation, try-compile and not exec_process is what is supposed
>> to be used for system introspection.  The build time environment is often different
>> than the cmake time environment, and if you are testing programs that will be run
>> at build time, try-compile/try_run is the only way to do that.  I assume that you are
>> planning to run makeinfo at build time, so it should be tested at build time.  Remember
>> cmake is not a build tool, but rather a build generator, and is not running during
>> the build.
>>   
>
> Ok, but given the shenanigans that must occur just to test if a tool 
> works, the wrapped up functionality really should make it into CMake.  
> I just can't abide that a user should have to do this much stuff to 
> test a tool.  I will write a macro and put it on the wiki.  What is 
> the process for getting user contributed macros into the Standard 
> CMake Modules?  That would be good information to have on the wiki, on 
> this page: http://www.cmake.org/Wiki/CMake_User_Contributed_Macros
>

I am finding it nearly impossible to write such a macro in practice.  
The problem is that a custom COMMAND has no understanding of native 
CMake paths.  So I must convert the paths to a native format, and 
FILE(TO_NATIVE_PATH ...) does not properly escape and quote the path for 
use by COMMAND.  Also, the COMMAND string needs to be saved somehow.  It 
needs to be used by TRY_COMPILE, and again by my CMakeLists.txt, so that 
I'm doing exactly the same thing each time.  Saving the string is 
problematic because passing the string around tends to destroy the 
quoting.  I have put a full work day into this, for what should be a 
fairly trivial tool test, and I still don't quite have something that 
works.  I may yet come up with an interface that does work, but I 
definitely wouldn't expect most CMake users (even experienced ones) to 
go through all this pain.

What I'm saying is, tool testing is very weak in CMake, and a better way 
is needed.  When/if I get to the end of this tunnel, I will make a 
specific recommendation rather than just complaining.


Cheers,
Brandon Van Every


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