[CMake] Problem when using variable_watch with Visual Studio generator in 3.4.1

[David Cole]

Out of curiosity, what output do you get (with 3.4.1) when you comment out
your call to variable_watch? Do you still get error output, but without
strange symbols in it? Or is there no error output in that case?


On Thursday, December 10, 2015, Yves Frederix <yves.frederix+cmake at gmail.com>
wrote:

> Hi all,
>
> I am experiencing problems during the CMake configure step when using
> the function variable_watch. Consider the following minimal CMakeLists
> file:
>
>   cmake_minimum_required(VERSION 3.4)
>   project(test CXX)
>
>   function(myhook _variable _access _value _current_list_file _stack)
>     if("${_value}" STREQUAL "")
>       # Do nothing
>     endif()
>   endfunction()
>
>   variable_watch(CMAKE_CURRENT_LIST_DIR myhook)
>   find_package(PythonInterp REQUIRED)
>
>
> When configuring on Windows using CMake 3.4.1 with the Visual Studio
> generator (I tried both VS2012 and VS2015), the process fails with an
> error message (notice the strange symbols at the beginning of the line
> mentioning FindPackageMessage.cmake):
>
>   -- Detecting CXX compile features - done
> CMake Error at
> C:/Tools/CMake_3.4.1/share/cmake-3.4/Modules/FindPackageHandleStandardArgs.cmake:142
> (include):
>   include could not find load file:
>
>     L☺/Tools/CMake_3.4.1/share/cmake-3.4/Modules/FindPackageMessage.cmake
> Call Stack (most recent call first):
>   C:/Tools/CMake_3.4.1/share/cmake-3.4/Modules/FindPythonInterp.cmake:161
> (include)
>   CMakeLists.txt:12 (find_package)
>
>
>   CMake Error at
>
> C:/Tools/CMake_3.4.1/share/cmake-3.4/Modules/FindPackageHandleStandardArgs.cmake:379
> (FIND_PACKAGE_MESSAGE):
>   Unknown CMake command "FIND_PACKAGE_MESSAGE".
>   Call Stack (most recent call first):
>     C:/Tools/CMake_3.4.1/share/cmake-3.4/Modules/FindPythonInterp.cmake:162
> (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
>     CMakeLists.txt:12 (find_package)
>
>
> I did some more testing, and the configuration step is successful when:
> - using CMake 2.8.12 or 3.4.0
> - using 3.4.1 (or older versions) on osx (I did not try linux)
> - removing the 'CXX' in the project call or removing the project call
> entirely
> - removing the check for _value inside the function
>
> It seems that for some reason adding the watch (which actually only
> does read-only access), the contents of the CMAKE_CURRENT_LIST_DIR
> variable is messed up somehow. Could I have run into some corner case
> behavior here?
>
> Maybe it is also useful to mention how I ended up in this situation.
> My requirement was to run some custom code as the very last step of
> the configure process. The solution I found was based on using
> variable_watch (see
>
> http://stackoverflow.com/questions/15760580/execute-command-or-macro-in-cmake-as-last-step-before-configure-step-finishes#15824843
> ),
> but apparently this is not a very robust solution. Are there possibly
> better ways of accomplishing the same thing?
>
> Thanks!
>
> Regards,
> Yves
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