Using generator expression with add_library

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Using generator expression with add_library

David Aldrich-2

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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Re: Using generator expression with add_library

Petr Kmoch
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 <[hidden email]> 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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Re: Using generator expression with add_library

David Aldrich-2
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 <[hidden email]> 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 <[hidden email]> 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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Re: Using generator expression with add_library

Andrew Fuller-2
Another option is to use BUILD_SHARED_LIBS to control static vs. shared.  Set it to false on MSVC and true everywhere else, then omit the library type in the add_library calls that you wish to have controllable behaviour.  Those add_library calls will then consult BUILD_SHARED_LIBS to determine whether to generate a static or shared lib.

From: CMake <[hidden email]> on behalf of David Aldrich <[hidden email]>
Sent: November 7, 2019 3:52 AM
To: Petr Kmoch <[hidden email]>
Cc: CMake MailingList <[hidden email]>
Subject: Re: [CMake] Using generator expression with add_library
 
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 <[hidden email]> 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 <[hidden email]> 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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Kitware offers various services to support the CMake community. For more information on each offering, please visit:

CMake Support: http://cmake.org/cmake/help/support.html
CMake Consulting: http://cmake.org/cmake/help/consulting.html
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