[CMake] Cross compiling in Win32 environment doesn't work

[Martin Kupke]

Hi Alex,

sorry for sending mails in HTML format (hopefully the mail client is now 
configured correctly).
You'll find my answers to your comments below.

On 20.09.11 05:29, Alexander Neundorf wrote:
> Hi,
>
> can you please adjust your mail client so it doesn't send HTML mails ?
>
> On Monday, September 19, 2011 04:57:32 PM Martin Kupke wrote:
>>   That's a hint, I changed my toolchain file "toolchain_ppc.cmake" to the
>> following: INCLUDE(CMakeForceCompiler)
>>   set(CMAKE_SYSTEM_NAME "Discovery")
>>
>>   if(CMAKE_CROSSCOMPILING)
>>   message("Cross Compiling")
>>   endif(CMAKE_CROSSCOMPILING)
>>
>>   # which compilers to use for C and C++
>>   set(CMAKE_C_COMPILER "C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe")
>>   set(CMAKE_FORCE_C_COMPILER "C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe")
>>   set(CMAKE_C_FLAGS "-tPPCVLEEN:simple")
>>
>>   Then I created a folder with the name Platform containing a file with
>> CMAKE_SYSTEM_NAME which is Discovery ->  at this point I had already
>> problems, because CMake doesn't use as described the filename with .cmake
>> extension. The filename in the Platform folder has to have the name from
>> CMAKE_SYSTEM_NAME without the extension .cmake (even the documentation
>> says something different). I checked this by adding the output of a
>> message("SYSTEM_NAME=Discovery").
> The filename must be Discovery.cmake in your case.
> Did you say this didn't work ?
> This file must be either in the cmake Modules/Platfom/ directory, or in a
> subdirectory Platform/ of a directory which is in CMAKE_MODULE_PATH.
Yes, I created the folder Platform in my CMAKE_MODULE_PATH and within 
this folder the file Discovery.cmake.
This doesn't work! I checked it using the message tag to output a string 
on the console.
After renaming the Discovery.cmake to only basename Discovery without 
the extension .cmake, the file was included.
So, the extension .cmake isn't correct...even it is described in the 
documentation.
The output of the CMake tool, if using the CMAKE_SYSTEM_NAME set to 
"Discovery":
########################### snip ###########################
D:\novero\Discovery\impl\target\CarIF_Appl\output>cmake -G "NMake 
Makefiles" -D CMAKE_TOOLCHAIN_FILE="..\toolchain_ppc.cmake" ..
Cross Compiling
-- The C compiler identification is unknown
-- Check for working C compiler: c:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe
System is unknown to cmake, create:
Platform/Discovery to use this system, please send your config file to 
cmake at www.cmake.org so it can be added to cmake
-- Check for working C compiler: 
c:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe --works
-- Detecting C compiler ABI info
System is unknown to cmake, create:
Platform/Discovery to use this system, please send your config file to 
cmake at www.cmake.org so it can be added to cmake
-- Detecting C compiler ABI info - done
C compiler: c:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe
C flags:  -tPPCVLEEN:simple
Mein CMakeLists.txt File
-- Configuring done
-- Generating done
-- Build files have been written to: 
D:/novero/Discovery/impl/target/CarIF_Appl/output
########################### snap ###########################
It seems to work, even there are some hints that CMake doesn't know the 
system Discovery.
I fixed the problem by using the CMAKE_SYSTEM_NAME set to "Generic".
With "Generic" I need a configuration file in the Platform folder named 
to "Generic-dcc" with the compile flags.
The name in the Platform folder again is used without the extension .cmake!
"Generic" needs to be added with "-dcc" because of the Base name of the 
dcc.exe compiler.
This now works and creates the Makefile in the output folder as wanted, 
without any errors / warnings ...
>
>>   The Platform/Discovery file contains the lines:
>>   message("SYSTEM_NAME=Discovery")
>>   set(CMAKE_FORCE_C_COMPILER "C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe")
>>   set(CMAKE_C_COMPILER "C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe")
>>   set(CMAKE_C_FLAGS "-tPPCVLEEN:simple")
>>   set(CMAKE_FORCE_C_FLAGS "-tPPCVLEEN:simple")
>>   set(CMAKE_FORCE_CXX_COMPILER
>> "C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe") set(CMAKE_CXX_COMPILER
>> "C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe") set(CMAKE_CXX_FLAGS
>> "-tPPCVLEEN:simple")
>>   set(CMAKE_MAKE_PROGRAM "D:/novero/Discovery/impl/win32/nmake/nmake.exe")
> That last line should not be necessary.
I thought this would help to point to the nmake tool in the Makefile, in 
case it is not in the search path of the system.
>>   Then I call from the command line the CMake tool with the parameters:
>>   D:\novero\Discovery\impl\target\CarIF_Appl\output>cmake -G "NMake
>> Makefiles" -D CMAKE_TOOLCHAIN_FILE="..\toolchain_ppc.cmake" ..
>>
>>   The following output will be produced:
>>   ********************* snip output *********************
>>   Cross Compiling
>>   -- The C compiler identification is unknown
>>   -- The CXX compiler identification is unknown
>>   SYSTEM_NAME=Discovery
>>   SYSTEM_NAME=Discovery
>>   -- Check for working C compiler:
>> C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe System is unknown to cmake,
>> create:
>>   Platform/Discovery to use this system, please send your config file to
>> cmake at www .cmake.org so it can be added to cmake
>>   -- Check for working C compiler:
>> C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe -- broken
>>   CMake Error at C:/Program Files/CMake
>> 2.8/share/cmake-2.8/Modules/CMakeTestCComp iler.cmake:52 (MESSAGE):
>>     The C compiler "C:/WindRiver/diab/5.9.0.0/WIN32/bin/dcc.exe" is not able
>> to compile a simple test program.
>>
>>     It fails with the following output:
>>
>>      Change Dir:
>> D:/novero/Discovery/impl/target/CarIF_Appl/output/CMakeFiles/CMak eTmp
>>
>>     Run Build Command:nmake /NOLOGO "cmTryCompileExec\fast"
>>
>>           nmake -f CMakeFiles\cmTryCompileExec.dir\build.make /nologo -L
>>     CMakeFiles\cmTryCompileExec.dir\build
>>
>>           "C:\Program Files\CMake 2.8\bin\cmake.exe" -E
>> cmake_progress_report
>> D:\novero\Discovery\impl\target\CarIF_Appl\output\CMakeFiles\CMakeTmp\CMak
>> eFil es
>>     1
>>
>>     Building C object CMakeFiles/cmTryCompileExec.dir/testCCompiler.c.obj
>>
>>           C:\WindRiver\diab\5.9.0.0\WIN32\bin\dcc.exe -o
>>     CMakeFiles\cmTryCompileExec.dir\testCCompiler.c.obj -c
>>
>> D:\novero\Discovery\impl\target\CarIF_Appl\output\CMakeFiles\CMakeTmp\test
>> CCom piler.c
>>
>>
>>     Target Unknown.  Use the -t option or set a default target with dctrl -t
>>
>>     NMAKE : fatal error U1077: 'C:\WINDOWS\system32\cmd.exe' : return code
>>     '0x1'
>>
>>     Stop.
>>
>>     NMAKE : fatal error U1077: 'C:\WINDOWS\system32\cmd.exe' : return code
>>     '0x2'
>>
>>     Stop.
>>
>>     CMake will not be able to correctly generate this project.
>>   Call Stack (most recent call first):
>>     CMakeLists.txt:2 (project)
>>
>>
>>   -- Configuring incomplete, errors occurred!
>>   You have changed variables that require your cache to be deleted.
>>   Configure will be re-run and you may have to reset some variables.
>>   The following variables have changed:
>>   CMAKE_CXX_COMPILER= cl
>>
>>   -- Generating done
>>   -- Build files have been written to:
>> D:/novero/Discovery/impl/target/CarIF_Appl/ output
>>
>>   ********************* snap output *********************
>>
>>   1.) with the output SYSTEM_NAME=Discovery I can see that the platform file
>> is used 2.) the compilation doesn't complete, because the CMAKE_C_FLAGS
>> are still not used
> They are initialized later on.
> There is a set of variables which are used for initialization, I think it's
> name is CMAKE_C_FLAGS_INIT .
That was the real needed information which was never given, not in the 
FAQ...not in the Tutorial...
I was studying the file C:\Program Files\CMake 
2.8\share\cmake-2.8\Modules\CMakeCInformation.cmake.
There I found the base initialization of the variables and could solve 
my problem.
Your information above would have saved me a lot of hours... ;-)
>> 3.) why do I have to have a CXX (C++) compiler, even if
>> I don't need it in my embedded solution
> By default cmake enables C and C++.
> If you put a
> project(MyProject C)
> into your toplevel CMakeLists.txt, only the C language will be enabled, not
> C++.
That is even a good information and I tested it -> fine!
>> 4.) is there any reason why CMake
>> needs to know my system? I want just to compile some files... (wondering)
> Yes. It needs this information to be able to know e.g. search locations for
> the find_xxx() calls, for file prefixes and suffixes, for knowing the compiler
> flags for this compiler on this OS
Specially in embedded environment with different possible OS, I think 
CMake can't know everything.
So the best way would be to give the developer a way to configure all by 
it's own.
 From my point of view (I'm still beginner with CMake) this is possible, 
you should even know how to do.

There is still one question open (not really project relevant to me, but 
interesting):
The default setting uses the C compiler always with the parameters -o 
[output file] -c [source file]
I think for most of the C compilers this matches, but what if they use 
different parameters for output and source?
Surely there will be a way to modify that, but I didn't found a note 
where / how to configure it.

> Alex
Alex, many thanks for your reply with the many useful information.

Best regards,
Martin...