[CMake] if( defined xxx ) does not work as (I) expected

[Michael Hufer]

Hi all,
I am new to CMake and am currently switching the make system for our X-Gen 
product to CMake.
Since the project contains a lot of shared libraries I wrote a macro to ease 
the writing of CMakeLists.txt for them. The macro receives a list of 
"external" libraries this library depends on. Some of these externals require 
extra defines or link flags and I collect them in the macro like this:
---
foreach( EXT ${EXTERNAL_LIBS} )
  [...]
  if( DEFINED ${EXT}_DEFINES )
    set( EXT_DEFINES "${EXT_DEFINES} ${${EXT}_DEFINES}" )
  endif( DEFINED ${EXT}_DEFINES )
 [...]
endforeach( EXT ${EXTERNAL_LIBS} )
[...]
if( DEFINED EXT_DEFINES )
  set_source_files_properties( $MODULE_SOURCES} PROPERTIES COMPILE_FLAGS 
${EXT_DEFINES} )
endif( DEFINED EXT_DEFINES )
---
(the macro is defined in cmake/XGen-Macros.cmake in the attached zip-file).
while the first 'if(defined ${EXT}_DEFINES)'  works as expected the second 
'if( DEFINED EXT_DEFINES )' where I check if actually any of the 'externals' 
for this library needs extra defines is always false even if the message() 
inserted before reports that this variable is in fact defined and shows its 
value.
The handling of extra link flags is identical and there also the first 
'if-defined' works as expected but the second does not...

I checked and double checked the macrocode, inserted debug messages etc. and 
don't see any obvious errors. 
So what am I doing wrong or did I actually find a bug in cmake?

Cheers,
	Micha.
-- 
Michael Hufer        | EMail: mailto:Michael.Hufer at swissrisk.com
Software Developer   | WWW:   http://www.swissrisk.com
SWISSRISK AG         | Phone: ++49 69 50952 - 0
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