[cmake-developers] [CMake 0014359]: [FindSWIG] SWIG detection fails when cross-compiling

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://public.kitware.com/Bug/view.php?id=14359 
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Reported By:                Michel Zou
Assigned To:                
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Project:                    CMake
Issue ID:                   14359
Category:                   Modules
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
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Date Submitted:             2013-08-14 18:49 EDT
Last Modified:              2013-08-14 18:49 EDT
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Summary:                    [FindSWIG] SWIG detection fails when cross-compiling
Description: 
The detection of swig fails when cross-compiling, here's why:

When cross-compiling, we do not want find_path to find files in the host tree,
so we set the root path to the target libs and includes:
set ( CMAKE_FIND_ROOT_PATH /usr/i386-mingw32 )
set ( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )

but we never want cmake to find utils (like swig, awk, bc, etc...) in the target
tree but in the host prefix:
set ( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )

Swig uses 'swig -swiglib' to determine the location of it's internal library:
  execute_process(COMMAND ${SWIG_EXECUTABLE} -swiglib
    OUTPUT_VARIABLE SWIG_swiglib_output)

Then it uses find-path to check the library macros presence:
find_path(SWIG_DIR swig.swg PATHS ${SWIG_swiglib_output})

But with CMAKE_FIND_ROOT_PATH_MODE_INCLUDE set to ONLY, the path cannot be found
in the host paths, and the required SWIG_DIR is not found ; the detection fails:
-- Could NOT find SWIG (missing:  SWIG_DIR)







Steps to Reproduce: 
Try to find swig while crosscompiling:

- in CMakeLists:
find_package(SWIG)

- in ToolChain-i386-mingw32:
set ( CMAKE_SYSTEM_NAME Windows )
set ( CMAKE_C_COMPILER i386-mingw32-gcc )
set ( CMAKE_FIND_ROOT_PATH /usr/i386-mingw32 )
set ( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )
set ( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY )
set ( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )

Additional Information: 
We could also search in the host paths by passing CMAKE_FIND_ROOT_PATH_BOTH to
find_file:
find_path(SWIG_DIR swig.swg PATHS ${SWIG_swiglib_output}
CMAKE_FIND_ROOT_PATH_BOTH)

See the embedded path, tested with and without cross-compilation.

Regards,

M.
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Issue History 
Date Modified    Username       Field                    Change               
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2013-08-14 18:49 Michel Zou     New Issue                                    
2013-08-14 18:49 Michel Zou     File Added: cmake-swig-cross-compilation.patch  
                 
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