[CMake] Trouble with conditional generator expression inside target_link_libraries

[Eric Noulard]

Le jeu. 4 oct. 2018 à 16:06, Björn Blissing <bjorn.blissing at vti.se> a
écrit :

> Hello,
>
>
>
> I am having trouble with a conditional generator expression inside target
> link libraries, which seems to expand incorrectly (or at least not the way
> I expect).
>
>
>
> In short, I have a list of libraries that is found by a CMake module. The
> list is composed of a number of elements each preceded by “optimized” or
> “debug”, depending on if there are built for release or debug. These
> libraries should only be included if a boolean is set to true. I have tried
> to write a generator expression which only includes the list of libraries
> if this variable is set. But it seems that this expression gets expanded
> wrong.
>
>
>
> If I try to condense the problem to a minimum example, it would be
> something like this:
>
>
>
> LIST(APPEND MYLIB_LIBRARIES optimized foo)
>
> LIST(APPEND MYLIB_LIBRARIES debug foo_d)
>
>
>
> TARGET_LINK_LIBRARIES(target_name
>
>     PUBLIC
>
>         $<$<BOOL:TRUE>:${MYLIB_LIBRARIES}>
>
> )
>

I don't quite understand your usage here. The genex $<BOOL:TRUE> is always
true?
You must have something like:

$<$<BOOL:${CONDVAR}>:${MYLIB_LIBRARIES}>

with CONDVAR computed before that to HOLD TRUE/1 or FALSE/0
or something similar?

I would try to build a proper MYLIBS_DEBUG and MYLIBS_OPTIMIZED list out of
your MYLIB_LIBRARIES var

and then:

target_link_libraries(target_name
   PUBLIC
     $<$<CONFIG:Debug>:${MYLIBS_DEBUG}>
     $<$<CONFIG:Release>:${MYLIBS_OPTIMIZED}>

which may be easier to read.

Or may be I missed something in your explanation.


>
> This generator expression makes my target depend of the following
> libraries for the release build:
>
> foo.lib & optimized.lib
>
>
>
> And for the debug build:
>
> foo_d.lib, foo.lib & optimized.lib
>
>
>
> Which is obviously incorrect.
>
>
>
> Replacing the generator expression with an IF-statement instead works. But
> I would like to stick to generator expressions if possible to keep my CMake
> code consistent.
>
>
>
> How should I rewrite my generator expression to get the correct expansion?
>
>
>
> Regards,
>
> Björn
>
>
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-- 
Eric
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