[CMake] different behaviour of the same code

[Andy Cedilnik]

Hi Eddy,

The syntax ${${foo}} only works inside FOREACH and MACRO and even there
only for the actual arguments. For example:

MACRO(macro FOO)
  MESSAGE("${${FOO}}")
ENDMACRO(macro)

SET(BAR "Hello world")
macro(BAR)

will work because the argument ${FOO} is string replaced by BAR, which
is then evaluated to "Hello world". That said, the following will not work:

SET(BAR "Hello world")
SET(FOO BAR)
MACRO(macro)
  MESSAGE("${${FOO}}")
ENDMACRO(macro)

You should put feature request to cmake bug tracker www.cmake.org/Bug
for full support of ${${...}} syntax.

       Andy

Eddy Pronk wrote:

> Fiddling around with macros, I found out there is different behaviour
> of the same code [${${component}_lib}].
> Maybe usage of variables as in M2 is not a good idea, but the output
> seems unexpected.
>
> MACRO(M1 component)
>  MESSAGE("M1 called for ${component}")
>  MESSAGE(${${component}_lib}) # works
> ENDMACRO(M1)
>
> MACRO(M2)
>  MESSAGE("M2 called for ${component}")
>  MESSAGE(${${component}_lib}) # unexpected output
> ENDMACRO(M2)
>
> SET(foo_lib mylib)
>
> SET(component foo) # global scope
>
> M1(foo)
> M2()
>
> MESSAGE(${${component}_lib}) # unexpected output
>
>
> $ cmake --version
> cmake version 2.0.5
>
>
> Eddy Pronk
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-- 
Andy Cedilnik
Kitware Inc.