I am stuck with a problem for which I searched on various threads unsuccessfully.
I have a project built with autotools utilities. This project relies on preprocessor directives which activate blocks of code depending on the presence of libraries or other stuff.
The problem I am facing is that once the project is built, for example like:
./configure --enable-mpi=yes && make
(Note that --enable-mpi=yes is set to add -DMPI_LIB=1 to the list of compiler flags.)
If I rebuild the project like
./configure --enable-mpi=no && make
Nothing is done for make. I think it is normal behaviour as no files changed except compilation flags (-DMPI_LIB=0 in that case).
How then can I add a dependence on flag changes in Makefile.am ?
I came across this thread: Makefile trigger rebuild for C/C++ preprocessor directives. Unfortunately I do not know how to adapt this to Makefile.am as there seem to be pretty high limitations in conditionals handling in Makefile.am.
Thank you for any advice !
EDIT
I may have found a workaround, or maybe the right way of doing it in another thread how to force recompile when changing Makefile flags? (I am not much experienced with make). If I add Makefile as a dependency to my object files it does the job, e.g. recompiles whenever a compilation flag changed.
Related
I have a cmake project with the typical build folder setup. I would like to instruct cmake to append this line anywhere into its generated Makefile:
../make_include/my_stuff.defs
I imagine I could tail this onto the Makefile myself, but I feel like that would cause it to continually be marked as dirty and rebuild. Any help here?
I have seen solutions (How to get CMake to use existing Makefile?) which use an external project command but I would like something more simple / dumb then that.
I have a project which builds for PPC, the Toolchain is working correctly, i can build when the sysroot is installed under /opt/poky/1.5. Now i tried to move that Installation to the Project Directory (it is not a part of the Repository there, it is just installed there so it is not reliant on that fix path, so that everyone can check out the project and build it wothout setting up the sysroot under that fixed folder).
To achieve this I set CMAKE_SYSROOT to "${PROJECT_SOURCE_DIR}/poky" where the poky will be installed upon execution of a custom build script (the project also needs to build a secure image, so it is way simpler to use a build script instead of anything else, also this is convenient for jenkins).
Since the CMAKE_SYSROOT is build from the PROJECT_SOURCE_DIR which is different for the CMakeTestCCompiler Project, the cmake call fails teloling me that the CCompiler is broken of course. So I want to know, how I am supposed to get the CMakeTestCCompiler Project to compile with the same CMAKE_SYSROOT variable, without altering the CMakeTestCCompiler Project itself (of course).
Somehow I cannot find an answer anywhere, it seems that noone ever had this issue (which frankly i cannot understand, this should be a common setup in my opinion). (Or maybe i am just too much of a noob when it comes to CMAKE, which i will gladly admit)
I am not interested in solutions like: "JUST INSTALL IT IN A FIX PATH" or such... please, I need the setup like this, I have reasons for that.
THX for reading/trying/answering/helping
Have a nice day
EDIT1:
In CMakeLists.txt (top level CMakeFile so it should be used by any build):
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots")`
In ToolchainCMake (the one given to the cmake as CMAKE_TOOLCHAIN_FILE):
`SET(CMAKE_SYSTEM_NAME Linux)`
`SET(CMAKE_SYSTEM_VERSION 1)`
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots")`
`SET(COMPILER_ROOT ${PROJECT_SOURCE_DIR}/poky/sysroots/i686-pokysdk-linux/usr/bin/powerpc-poky-linux-gnuspe)`
`SET(CMAKE_C_COMPILER ${COMPILER_ROOT}/powerpc-poky-linux-gnuspe-gcc)`
`SET(CMAKE_CXX_COMPILER ${COMPILER_ROOT}/powerpc-poky-linux-gnuspe-g++)`
`MESSAGE("CMAKE_C_COMPILER: ${CMAKE_C_COMPILER}")`
`MESSAGE("CMAKE_CXX_COMPILER: ${CMAKE_CXX_COMPILER}")`
`MESSAGE("COMPILER_ROOT: ${COMPILER_ROOT}")`
`SET(CMAKE_FIND_ROOT_PATH ${SYS_ROOT}/ppce500v2-poky-linux-gnuspe)`
`SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)`
`SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)`
`SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)`
EDIT2:
I used the
`set(CMAKE_C_COMPILER_WORKS 1 CACHE INTERNAL "")`
`set(CMAKE_CXX_COMPILER_WORKS 1 CACHE INTERNAL "")`
settings to simulate the CMakeTestCCompiler build succeeding and realized that I am facing some additional problems: It seem that the packages are looked up on the system instead of the CMAKE_SYSROOT folder. Even tried the
`SET(CMAKE_FIND_ROOT_PATH ${CMAKE_SYSROOT})`
to try to force the search in there, but without luck. In the CMakeError.log I can see, that the compiler itself was configured with the prefix option that points to /opt/poky/1.5, the path that i want to "overwrite", now I am not sure if the compiler could even deal with an alternate path.
I felt the need to add these information, they not really add to the problem at hand.
ERRORS:
I also found some errors in the above cmake:
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots")`
must be
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots/ppce500v2-poky-linux-gnuspe")`
instead and therefor the
`SET(CMAKE_FIND_ROOT_PATH ${SYS_ROOT}/ppce500v2-poky-linux-gnuspe)`
changes to
`SET(CMAKE_FIND_ROOT_PATH ${CMAKE_SYSROOT})`
EDIT: Whole answer changed.
My first suspicion was that the problem is that value of ${PROJECT_SOURCE_DIR} is not known in CMAKE_TOOLCHAIN_FILE as it is processed before CMakeLists.txt. But this isn't true.
I had similar problem (CMake 2.8.12.2), everything worked OK, when I passed cross compiler by CC environment variable with --sysroot option, i.e. CMake was invoked as follows:
CC="arm-linux-gnueabi-gcc --sysroot=/path/to/sysroot" cmake /path/to/sources
When I switched to using toolchain file, CMake started to report that C compiler doesn't work.
To workaround this problem, I use CMakeForceCompiler package. Parts toolchain file (along with comments) I think are relevant:
include(CMakeForceCompiler)
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)
# Force compiler - only option that actually works
cmake_force_c_compiler (${TOOLCHAIN_PATH}/bin/arm-linux-gnueabi-gcc GNU)
cmake_force_cxx_compiler(${TOOLCHAIN_PATH}/bin/arm-linux-gnueabi-g++ GNU)
# NOTE: CMAKE_SYSROOT doesn't work as expected
add_definitions("--sysroot=${TOOLCHAIN_SYSROOT}")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --sysroot=${TOOLCHAIN_SYSROOT}" CACHE INTERNAL "" FORCE)
Note, that TOOLCHAIN_PATH and TOOLCHAIN_SYSROOT are my local variables set before.
I am currently having a bear of a time trying to compile a moderate sized library with a brand new toolchain, Assimp on Xcode6 with the new iOS 8.0 SDK.
Bundled with the project are various scripts and Xcode projects that have configurations for building on iOS, but unfortunately none of them work out of the box.
So far the farthest I have gotten is by using a build script which uses the cmake "Unix Makefiles" method to assemble static libs. Other methods would include using cmake to generate Xcode projects to use to build. I tried that also to no avail, and neither did the Xcodeproject that comes with the project in the repository (which I later learned was marked deprecated in one of the readme files).
Okay, so with this "Unix Makefiles" cmake script I have been able to generate some of the static libs (after manually forcing static lib generation inside the main CMakeLists.txt), but when it went on to build for i386 and x86_64 architectures for iPhoneSimulator it kept pulling in the headers for iOS which caused a torrent of compiler errors.
Luckily I followed a hunch and found assimp/code/CMakeFiles/assimp.dir/flags.make which is one of the cmake-generated files, and lo and behold, the entire cflags was in here, and once I removed the rogue header include path, the make call finally succeeds and I have my iPhoneSimulator static lib!
Okay so the question that I have is basically where do I get started when debugging these frustrating cmake problems. My relationship with cmake has always been a strained one because none of cmake's complexity and design principles ever made sense to me, and very infrequent are the times when cmake builds work for me out of the box... it is always something that almost works but then I have to spend hours debugging with make VERBOSE=1 and then haphazardly poking at generated files, which are of course all marked with warnings to not edit them as they are generated files.
I realize that some of the variables here are perhaps relevant to my troubles. But it isn't clear to me how I can debug these variables. Where do I go to print out these variables so that I can find which variable contains erroneous values? For example, in this most recent situation I had a -I flag that was cropping up in the wrong place. Luckily I was able to find a file that contained it using various large-hammer methods that involve grep but I am not close to actually fixing the build configuration to make the process any less painful in the future.
For complex CMakeLists.txt files I have found the variable_watch command can sometimes be useful (documentation here). It doesn't make it easy, but gives you another level of information.
I'm not asking this for just myself. I hope this question will be a reference for the many newbies who like me, found it utterly perplexing about what exactly what was going on behind the scenes when for such a small CMakeLists.txt file
cmake_minimum_required (VERSION 2.6)
project(Tutorial)
add_executable(Tutorial tutorial.cpp)
and such a small tutorial.cpp
int main() { return 0; }
there are so many files generated
CMakeCache.txt cmake_install.cmake Makefile
CMakeLists.txt tutorial.cpp
and a CMakeFiles folder with so many files and folders
CMakeCCompiler.cmake CMakeOutput.log Makefile.cmake
cmake.check_cache CMakeSystem.cmake progress.marks
CMakeCXXCompiler.cmake CMakeTmp TargetDirectories.txt
CMakeDetermineCompilerABI_C.bin CompilerIdC Tutorial.dir
CMakeDetermineCompilerABI_CXX.bin CompilerIdCXX
CMakeDirectoryInformation.cmake Makefile2
Not understanding what was going on behind the scenes (i.e: why so may files had to be generated and what their purpose was), was the biggest obstacle in being able to learn CMake.
If anyone knows, could you please explain it for the sake of posterity? What is the purpose of these files, and when I type cmake ., what exactly is cmake configuring and generating before it builds the project?
The secret is that you don't have to understand what the generated files do.
CMake introduces a lot of complexity into the build system, most of which only pays off if you use it for building complex software projects.
The good news is that CMake does a good job of keeping a lot of this messiness away from you: Use out-of-source builds and you don't even have to look at the generated files. If you didn't do this so far (which I guess is the case, since you wrote cmake .), please check them out before proceeding. Mixing the build and source directory is really painful with CMake and is not how the system is supposed to be used.
In a nutshell: Instead of
cd <source_dir>
cmake .
always use
cd <build_dir_different_from_source_dir>
cmake <source_dir>
I usually use an empty subfolder build inside my source directory as build directory.
To ease your pain, let me give a quick overview of the relevant files which CMake generates:
Project files/Makefiles - What you are actually interested in: The files required to build your project under the selected generator. This can be anything from a Unix Makefile to a Visual Studio solution.
CMakeCache.txt - This is a persistent key/value string storage which is used to cache value between runs. Values stored in here can be paths to library dependencies or whether an optional component is to be built at all. The list of variables is mostly identical to the one you see when running ccmake or cmake-gui. This can be useful to look at from time to time, but I would recommend to use the aforementioned tools for changing any of the values if possible.
Generated files - This can be anything from autogenerated source files to export macros that help you re-integrate your built project with other CMake projects. Most of these are only generated on demand and will not appear in a simple project such as the one from your question.
Anything else is pretty much noise to keep the build system happy. In particular, I never needed to care about anything that is going on inside the CMakeFiles subdirectory.
In general you should not mess with any of the files that CMake generates for you. All problems can be solved from within CMakeLists.txt in one way or the other. As long as the result builds your project as expected, you are probably fine. Do not worry too much about the gory details - as this is what CMake was trying to spare you of in the first place.
As stated on its website:
Cmake is cross-platform, open-source build system for managing the build process of software using a compiler-independent method
In most cases it is used to generate project/make files - in your example it has produced Makefile which are used to build your software (mostly on Linux/Unix platform).
Cmake allows to provide cross platform build files that would generate platform specific project/make files for particular compilation/platform.
For instance you may to try to compile your software on Windows with Visual Studio then with proper syntax in your CMakeLists.txt file you can launch
cmake .
inside your project's directory on Windows platform,Cmake will generate all the necessary project/solution files (.sln etc.).
If you would like to build your software on Linux/Unix platform you would simply go to source directory where you have your CMakeLists.txt file and trigger the same cmake . and it will generate all files necessary for you to build software via simple make or make all.
Here you have some very good presentation about key Cmake functionalities http://www.elpauer.org/stuff/learning_cmake.pdf
EDIT
If you'd like to make platform dependent library includes / variable definitions etc. you can use this syntax in CMakeLists.txt file
IF(WIN32)
...do something...
ELSE(WIN32)
...do something else...
ENDIF(WIN32)
There is also a lot of commands with use of which you are able to prevent the build from failing and in place Cmake will notify you that for instance you do not have boost libraries filesystem and regex installed on your system. To do that you can use the following syntax:
find_package(Boost 1.45.0 COMPONENTS filesystem regex)
Having checked that it will generate the makefiles for appropriate system/IDE/compiler.
Exactly how CMake works is a question for the developers, so this question can't be answered here.
However we can give a touch of useful guidance as far as when you should use CMake and when you therefore need to worry about how it works. I'm not a fan of "oh it just works" answers either - because, especially in software, NOTHING ever "just works" and you ALWAYS have to get into the nitty-gritty details at some point.
CMake is an industrial-strength tool. It automates several VERY complex process and takes into account many variables of which you may not be aware, especially as a fairly new developer, probably working with limited knowledge of all the operating systems and build tools CMake can handle. The reason so many files are generated and why things seem so complex is because all of those other systems are complex and must be accounted for and automated. Additionally there are the issues of "caching" and other time-saving features of the tool To understand everything in CMake would mean understanding everything in these build tools and OS's and all the possible combinations of these variables, which as you can imagine is impossible.
It's important to note that if you're not in charge of managing a large cross-platform build system, and your code base is a few KLOC, maybe up to 100KLOG, using CMake seems a little bit like using a 100,000 dollar forestry tree removal machine to remove weeds from your 2 foot by 2 foot flower garden. (By the way, if you've never seen such a machine, you should look for one on youtube, they're amazing)
If your build system is small and simple it's likely to be better to just write your own makefiles by hand or script them yourself. When your makefiles become unwieldy or you need to build a version of your system on another platform, then you can switch over to CMake. At that point, you'll have lots of problems to solve and you can ask more focused questions about it. In the meantime, check out some of the great books that have been written about CMake, or even better, write one yourself! 8)
I'm wondering how i can make a portable build system (step-by-step), i currently use cmake because it was easy to set up in the first place, with only one arch target, but now that i have to package the library I'm developing I'm wondering how is the best way to make it portable for arch I'm testing.
I know I need a config.h to define things depending on the arch but I don't know how automatic this can be.
Any other way to have a build system are warmly welcome!
You can just use CMake, it's pretty straightforward.
You need these things:
First, means to find out the configuration specifics. For example, if you know that some function is named differently on some platform, you can use TRY_COMPILE to discover that:
TRY_COMPILE(HAVE_ALTERNATIVE_FUNC
${CMAKE_BINARY_DIR}
${CMAKE_SOURCE_DIR}/alternative_function_test.cpp
CMAKE_FLAGS -DINCLUDE_DIRECTORIES=xxx
)
where alternative_function_test.cpp is a file in your source directory that compiles only with the alternative definition.
This will define variable HAVE_ALTERNATIVE_FUNC if the compile succeeds.
Second, you need to make this definition affect your sources. Either you can add it to compile flags
IF(HAVE_TR1_RANDOM)
ADD_DEFINITIONS(-DHAVE_TR1_RANDOM)
ENDIF(HAVE_TR1_RANDOM)
or you can make a config.h file. Create config.h.in with the following line
#cmakedefine HAVE_ALTERNATIVE_FUNCS
and create a config.h file by this line in CMakeLists.txt (see CONFIGURE_FILE)
CONFIGURE_FILE(config.h.in config.h #ONLY)
the #cmakedefine will be translated to #define or #undef depending on the CMake variable.
BTW, for testing edianness, see this mail
I have been using the GNU autoconf/automake toolchain which has worked well for me so far. I am only really focussed on Linux/x86 (and 64bit) and the Mac, which is important if you are building on a PowerPC, due to endian issues.
With autoconf you can check the host platform with the macro:
AC_CANONICAL_HOST
And check the endianness using:
AC_C_BIGENDIAN
Autoconf will then add definitions to config.h which you can use in your code.
I am not certain (have never tried) how well the GNU autotools work on Windows, so if Windows is one of your targets then you may be better off finding similar functionality with your existing cmake build system.
For a good primer on the autotools, have a look here:
http://www.freesoftwaremagazine.com/books/autotools_a_guide_to_autoconf_automake_libtool