[CMake] #cmakedefine and the #if vs #ifdef argument

[Michael Wild]

On 17. Jun, 2009, at 23:27, Alexander Neundorf wrote:

> On Thursday 11 June 2009, Hostile Fork wrote:
>> Hello list!
>>
>> As a learning exercise, I am adding CMake and CTest to a small open-
>> source library I made which currently has no build system:
>>
>> 	http://hostilefork.com/nstate/
>> 	http://hostilefork.com/nocycle/
>>
>> For the first step, I have been applying the "configure_file"
>> methodology to this header:
>>
>> 	http://github.com/hostilefork/nocycle/blob/1ac238aea7af9e02f3a49f0c7eb9910
>> 74c8eb3fd/NocycleSettings.hpp
>>
>> ( Following these directions:
>> http://www.vtk.org/Wiki/CMake_HowToDoPlatformChecks )
>>
>> It seems the #cmakedefine lines are replaced with one of these two
>> cases:
>>
>> 	#define VAR_THAT_IS_ON
>> 	/* #undef VAR_THAT_IS_OFF */
>>
>> However... in the past I have been persuaded by the argument that the
>> use of #if is superior to #ifdef for conditional compilation.
>> ( Roddy's comment here on StackOverflow summarizes the advantages
>> pretty well:
>> http://stackoverflow.com/questions/135069/ifdef-vs-if-which-is-bettersafer
>> )
>>
>> Is it possible to get CMake to produce something more like:
>>
>> 	#define VAR_THAT_IS_ON 1
>> 	#define VAR_THAT_IS_OFF 0
>
> Did you try using
> #cmakedefine01 VAR_THAT_IS_ON
> I think this should do what you want.
>
> Alex
>

Now, that is useful! Sadly, it is undocumented and I never found it;  
this would have saved me quite some time...

Attached patch extends the doc to mention this feature.

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