[CMake] FindSDL.cmake and mingw / msys

[PA Galmes]

Hello,

I've been playing for some days with cmake, and I have
to say that I quite love the way it works. But while trying
to compile a sourceforge project under Windows using
MSYS, I run into a problem.

I do not know if the problem is related to the
CMakeLists.txt that I did not wrote correctly or to an
issue into the FindSDL.cmake. That's why I write here.

What I did:

- I wrote the CMakeLists.txt under Linux. There,
everything compiled like a charm. I added the code
of my CMakeLists.txt at the end of the mail

- Under Windows, I then generated the make files for
MSYS and tried to compile it using msys and mingw:


$ make
Scanning dependencies of target bloodybeard
[ 25%] Building CXX object CMakeFiles/bloodybeard.dir/main.obj
[ 50%] Building CXX object CMakeFiles/bloodybeard.dir/qGameEngine.obj
[ 75%] Building CXX object CMakeFiles/bloodybeard.dir/moc_qGameEngine.obj
Linking CXX executable bloodybeard.exe
CMakeFiles/bloodybeard.dir/qGameEngine.obj(.text+0x1d7):qGameEngine.cpp:
undefined reference to `SDL_Init'
CMakeFiles/bloodybeard.dir/qGameEngine.obj(.text+0x1eb):qGameEngine.cpp:
undefined reference to `SDL_WM_SetCaption'
...

So, the SDL lib is not correctly linked under Windows/MSYS.

I then checked the "build.make" file generated. It  does
not includes all the needed link flags needed for SDL under
mingw ( -lmingw32 -lSDLmain -lSDL -lmwindows).

Why aren't those flags added? It looks like the SDL_LIBRARY
variable is empty, but why ?

I would need some help to investigate further.

- In the FindSDL.cmake, there is a specific part related to MINGW:

# MinGW needs an additional library, mwindows
# It's total link flags should look like -lmingw32 -lSDLmain -lSDL
-lmwindows
# (Actually on second look, I think it only needs one of the m* libraries.)
IF(MINGW)
  SET(MINGW32_LIBRARY mingw32 CACHE STRING "mwindows for MinGW")
ENDIF(MINGW)

So, why doesn't this work ? Is there a specific MSYS flag to add?


I have a few workarounds in order to compile my project, but would
like to help.


Regards,
Pierre-André Galmes


I - Links:

The project is at the following adress:
http://sourceforge.net/projects/bloodybeard

You can access to the svn source if you want to.


II - CMakeLists.txt :


# The Qt flags
# I do not need QtGui.
SET(QT_DONT_USE_QTGUI True)


# find and setup Qt4 for this project
# SDL for this project
find_package(Qt4 REQUIRED)
find_package(SDL REQUIRED)
find_package(SDL_image REQUIRED)

include(${QT_USE_FILE})

INCLUDE_DIRECTORIES(${SDL_INCLUDE_DIR})
INCLUDE_DIRECTORIES(${SDLIMAGE_INCLUDE_DIR})

LINK_LIBRARIES(${SDL_LIBRARY} ${SDLIMAGE_LIBRARY} ${SDLMAIN_LIBRARY})


# the variable "bloodybeard_SRCS" contains all .cpp files of this project
set(bloodybeard_SRCS
    main.cpp
    qGameEngine.cpp
)

SET(bloodybeard_MOC_HDRS
  qGameEngine.h
)

# After this call, bloodybeard_MOC_SRCS = moc_Class1.cxx moc_Class2.cxx
moc_Class3.cxx.
QT4_WRAP_CPP(bloodybeard_MOC_SRCS ${bloodybeard_MOC_HDRS})

ADD_EXECUTABLE(bloodybeard ${bloodybeard_SRCS} ${bloodybeard_MOC_SRCS})


# tell cmake to create .moc files for all files in the variable
bloodybeard_SRCS
# that require such a file.
# note: this assumes that you use #include "header.moc" in your files
qt4_automoc(${bloodybeard_SRCS})

# create an executable file named "bloodybeard" from the source files in the
# variable "bloodybeard_SRCS".
add_executable(bloodybeard ${bloodybeard_SRCS})

# link the "bloodybeard" target against the Qt libraries. which libraries
# exactly, is defined by the "include(${QT_USE_FILE})" line above, which
sets
# up this variable.
target_link_libraries(bloodybeard ${QT_LIBRARIES})






-- 
Pierre-André Galmes
Free Software consultant
StarXpert - www.starxpert.fr
6, rue Eugène Varlin - 75010 Paris
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