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windowscmake
Jan Schatz
Jan Schatz

Reputation: 365

CMAKE_INSTALL_PREFIX not added to CMAKE_SYSTEM_PREFIX_PATH after setting CMAKE_SYSTEM_NAME to Generic

I am cross-compiling a project with CMake. find_library fails to find a library that is located in ${CMAKE_INSTALL_PREFIX}/lib, because CMAKE_INSTALL_PREFIX is not being appended to CMAKE_SYSTEM_PREFIX_PATH as it should according to the documentation.

The cause for this is that I set CMAKE_SYSTEM_NAME to Generic in my toolchain file. I stripped down the toolchain file to this single command. Why does it affect the behaviour of CMAKE_INSTALL_PREFIX?

If I set CMAKE_SYSTEM_NAME to Linux or Windows, CMAKE_SYSTEM_PREFIX_PATH has some preset and also CMAKE_INSTALL_PREFIX is appended as expected.

Upvotes: 1

Views: 969

Answers (1)

Jan Schatz
Jan Schatz

Reputation: 365

I think the documentation is wrong here. Adding CMAKE_INSTALL_PREFIX to CMAKE_SYSTEM_PREFIX_PATH is not done automatically. This is done inside CMake modules that are specific to the Windows and Linux platforms (e.g. c:\Program Files\CMake\share\cmake-3.14\Modules\Platform\WindowsPaths.cmake on my computer).

To mimic the same behaviour for non-Windows and non-Linux platforms, you can do the following. In the toolchain file, define a unique system name and also add the current directory to CMAKE_MODULE_PATH so that Cmake will look for modules here:

set(CMAKE_SYSTEM_NAME "MySystem")
list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})

Then create a platform file called <CMAKE_SYSTEM_NAME>.cmake in a sub-folder called Platform (e.g. Platform\MySystem.cmake). Inside this file you can append CMAKE_INSTALL_PREFIX to CMAKE_SYSTEM_PREFIX_PATH:

# Copied from c:\Program Files\CMake\share\cmake-3.14\Modules\Platform\WindowsPaths.cmake 
if (NOT CMAKE_FIND_NO_INSTALL_PREFIX)
  list(APPEND CMAKE_SYSTEM_PREFIX_PATH
    # Project install destination.
    "${CMAKE_INSTALL_PREFIX}"
  )
  if(CMAKE_STAGING_PREFIX)
    list(APPEND CMAKE_SYSTEM_PREFIX_PATH
      # User-supplied staging prefix.
      "${CMAKE_STAGING_PREFIX}"
    )
  endif()
endif()

Upvotes: 1

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