OS specific instructions in CMAKE How to

Question

I am a beginner to CMAKE  Below is a simple cmake file which works well in mingw environment windows  The problem is clearly with target link libraries   function of CMAKE where I am linking libwsock32 a  In windows this works and I get the results    However  as expected  in Linux  the  usr bin ld will look for -lwsock32 which is NOT there on the Linux OS    My Problem is  How do I instruct CMAKE to avoid linking wsock32 library in Linux OS     Any help will be greatly appreciated    My Simple CMake file     PROJECT biourl   set    PROJECT NAME  headers   BioSocketAddress h    BioSocketBase h   BioSocketBuffer h   BioSocketCommon h    BioSocketListener h    BioSocketPrivate h    BioSocketStream h   BioUrl h BioDatabase h    set    PROJECT NAME  sources BioSocketAddress C  BioSocketBase C  BioSocketCommon C BioSocketStream C  BioUrl C BioDatabase C    add library   PROJECT NAME  STATIC     PROJECT NAME  headers      PROJECT NAME  sources       linkers  find library ws NAMES wsock32 PATHS   PROJECT SOURCE DIR  NO SYSTEM ENVIRONMENT PATH NO DEFAULT PATH   target link libraries   PROJECT NAME  bioutils wsock32   install  TARGETS   PROJECT NAME         RUNTIME DESTINATION bin        LIBRARY DESTINATION lib        ARCHIVE DESTINATION lib archive

User · Answer

I want to leave this here because I struggled with this when compiling for Android in Windows with the Android SDK.

CMake distinguishes between TARGET and HOST platform.

My TARGET was Android so the variables like CMAKE_SYSTEM_NAME had the value "Android" and the variable WIN32 from the other answer here was not defined. But I wanted to know if my HOST system was Windows because I needed to do a few things differently when compiling on either Windows or Linux or IOs. To do that I used CMAKE_HOST_SYSTEM_NAME which I found is barely known or mentioned anywhere because for most people TARGEt and HOST are the same or they don't care.

Hope this helps someone somewhere...

User · Answer

Use some preprocessor macro to check if it s in windows or linux  For example   ifdef WIN32 LIB    elif   GNUC   LIB wsock32  endif   include -l  LIB  in you build command   You can also specify some command line argument to differentiate both

User · Answer

You have some special words from CMAKE  take a look   if   CMAKE SYSTEM NAME  STREQUAL  Linux          do something for Linux else        do something for other OS

User · Answer

Use  if  WIN32       do something endif  WIN32    or  if  UNIX       do something endif  UNIX    or   if  MSVC       do something endif  MSVC    or similar  see CMake Useful Variables and CMake Checking Platform

User · Answer

Try that   if WIN32      set ADDITIONAL LIBRARIES wsock32  else       set ADDITIONAL LIBRARIES     endif    target link libraries   PROJECT NAME  bioutils   ADDITIONAL LIBRARIES     You can find other useful variables here

User · Answer

Generator expressions are also possible   target link libraries      target name     PUBLIC         libA           lt   lt PLATFORM ID Windows gt  wsock32 gt      PRIVATE           lt   lt PLATFORM ID Linux gt  libB gt          libC     This will link libA  wsock32  amp  libC on Windows and link libA  libB  amp  libC on Linux  CMake Generator Expressions

User · Answer

In General  You can detect and specify variables for several operating systems like that   Detect Microsoft Windows  if WIN32        for Windows operating system in general endif     Or   if MSVC OR MSYS OR MINGW        for detecting Windows compilers endif     Detect Apple MacOS  if APPLE        for MacOS X or iOS  watchOS  tvOS  since 3 10 3  endif     Detect Unix and Linux  if UNIX AND NOT APPLE        for Linux  BSD  Solaris  Minix endif     Your specific linker issue  To solve your issue with the Windows-specific wsock32 library  just remove it from other systems  like that   if WIN32      target link libraries   PROJECT NAME  bioutils wsock32  else     target link libraries   PROJECT NAME  bioutils  endif

User · Answer

Given this is such a common issue  geronto-posting       if UNIX AND NOT APPLE          set LINUX TRUE      endif          if NOT LINUX  should work  too  if you need that     if LINUX           message STATUS   gt  gt  gt  Linux             linux stuff here     else           message STATUS   gt  gt  gt  Not Linux             stuff that should happen not on Linux      endif     CMake boolean logic docs  CMake platform names  etc

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