[CMake] Using generator expression with add_library

[David Aldrich]

Thank you. So I guess I can make it as simple as:

if(MSVC)
    add_library(${_star_lib_name} STATIC "")
else()
    add_library(${_star_lib_name} SHARED "")
endif()

I just wondered if there was a more elegant way.

On Thu, Nov 7, 2019 at 11:45 AM Petr Kmoch <petr.kmoch at gmail.com> wrote:

> Hi.
>
> The argument STATIC or SHARED is processed at CMake configure time (that
> is, when CMake is executing the add_library() command). However, generator
> expressions are only evaluated at generate time, which comes only after all
> CMake code is processed.
>
> Fortunately for you, compiler ID is something that is already known at
> configure time, meaning you don't need to use a genex to read it. You can
> just do this:
>
> if(MSVC)
>   set(LibType STATIC)
> else()
>   set(LibType SHARED)
> endif()
> add_library(
>   ${_star_lib_name}
>   ${LibType}
>   ...
> )
>
> (Feel free to modify the if(), use CMAKE_<LANG>_COMPILER_ID (
> https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_COMPILER_ID.html)
> etc. as necessary).
>
> Petr
>
> On Thu, 7 Nov 2019 at 12:28, David Aldrich <david.aldrich.ntml at gmail.com>
> wrote:
>
>> I want to build a shared library for Linux and a static library for
>> Windows. So I have tried:
>>
>>  set (_star_lib_name "StdStars")
>>
>>  add_library(${_star_lib_name}
>>              $<$<CXX_COMPILER_ID:GNU>:SHARED>
>>              $<$<CXX_COMPILER_ID:MSVC>:STATIC>
>>              ""
>>  )
>>
>> but that gives me error:
>>
>> CMake Error at C:/SVNProj/zodiac/branches/TRY_TML_CMake_3Oct2019/StarLibs/StdStars/CMakeLists.txt:7 (add_library):
>> Cannot find source file:
>>
>>     STATIC
>>
>>   Tried extensions .c .C .c++ .cc .cpp .cxx .cu .m .M .mm .h .hh .h++ .hm
>>   .hpp .hxx .in .txx
>>
>> What is the correct way of doing this please?
>> --
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