When it comes to using the terminal to build libraries manually and such I unfortunately do not have much experience and I'm stuck a bit here.
I've downloaded a library for objective-c which came with makefiles and such.
I can see that the folder also contains an executable file called "libtool", I did some searching and I suppose this is the program I have to use to build the neccessary .a files? Unfortunately I couldn't really find any useful article for this that seemed to work.
The folder for the library contains some .sh files, .pc files and also some .la files, but I'm a bit unsure of which ones I have to use as input to the libtool program to compile them into a .a file.
So my question is what files do you have to input into libtool to compile them into the necessary .a file? And what commands do you use exactly to accomplish this?
Thank you all for your time :)
First a little introduction to static libraries:
Static libraries in Unix environments (like Mac OSX, and Linux too) are actually just an archive of object files created by the ar command line program.
That is what the .a extension stands for: Archive.
To create a static library with some object files you can use the command like this:
ar crv libmy_library.a objectfile1.o objectfile2.o
As for your actual question, libtool should be called automatically from the makefile, creating the library, which is the file ending in .la. However, this is not the real library, the real library is in a hidden directory. You can find it by doing e.g.
find . -name '*.a'
But like I said, the makefile should already take care of everything, including installing the correct library in the correct place when you do e.g. make install.
For information about libtool, see this site.
Related
I'm trying to use find_package to include libraries in CMake.
This question talks about how to tell CMake to link to the GMP library (external). I am trying to follow the steps of the answer there but do not have any of the <name>Config.cmake or <name>-config.cmake files, as mentioned by some of the comments, which appears to be the default. The answer does not mention any solution for when you don't know how to get/find these files. The comments to that answer link to an old website (external) with a lot of broken links, that describes a list of Load Modules. It's unclear to me where these modules come from and how to get them.
According to the official CMake documentation (external), if the configuration files are not found, find_package falls back from "Module Mode" to "Config Mode". I don't understand what this means and in what cases this would be relevant, especially since the documentation discourages reading about "Config Mode".
The documentation says that
The file is first searched in the CMAKE_MODULE_PATH, then among the Find Modules provided by the CMake installation.
I am still confused about whether these configuration files are supposed to come with CMake or with the library in question and where they are supposed to be located. Probably both are possible but how does one know in a specific case?
Example code, trying to follow modern best practices:
# CMakeLists.txt (not working)
cmake_minimum_required(VERSION 3.2) # I have no idea what version I actually need
project (GMP_demo_project)
# Enable C++17 standard
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
find_package(GMP REQUIRED)
# Create the executable from sources
add_executable(GMP_demo GMP_demo.cpp)
target_link_libraries(GMP_demo gmp gmpxx)
The code outputs an error message along the lines of
CMake Error at CMakeLists.txt:10 (find_package):
By not providing "FindGMP.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "GMP", but
CMake did not find one.
Could not find a package configuration file provided by "GMP" with any of
the following names:
GMPConfig.cmake
gmp-config.cmake
Add the installation prefix of "GMP" to CMAKE_PREFIX_PATH or set "GMP_DIR"
to a directory containing one of the above files. If "GMP" provides a
separate development package or SDK, be sure it has been installed.
Question: How does one, in general, obtain and organize these configuration files (CMake Load Modules)? How can one expect another user to have these files on his system? My question is intended to be general and only use GMP as an example (although I am in fact interested in being able to use it).
Just as an aside, I can compile, link and execute my demo code just fine using gcc GMP_demo.cpp -lstdc++ -lgmp after having installed GMP as suggested by the library documentation. The problem is just getting CMake to do it. I can also just give CMake the absolute path of the library, which would of course be much easier but not portable (assuming one can get find_package to actually work and be portable with reasonable amounts of work).
How does one, in general, obtain and organize these configuration files (CMake Load Modules)?
Broadly speaking, there are three buckets these fall into:
Files provided directly by the package. This is the ideal solution, and would be what CMake calls Config mode. There would be a file called GMPConfig.cmake which cmake could find by searching preconfigured paths, or by providing a specific path at configuration time (cmake -DGMP_Dir=/path/to/GMP/install/root). The advantages of this approach are that generation of GMPConfig.cmake is mostly automatic, and the libraries can include things like installation paths and compilation flags. The disadvantage is that the library develops have to actually go to the effort of leveraging modern CMake, and not everybody does this.
Files provided directly by CMake. For common packages (e.g., boost) CMake ships FindXXX.cmake files that search well-known paths and take care of this for you. These work identically to the above from an end-user perspective, but which Find modules are available depends on the version of CMake you have installed.
Files provided by some random person that are copy/pasted into projects. How these works depends on the person who wrote it, so you'll have to read their documentation. Use your favorite search engine and try to find FindGMP.cmake, then drop it in a module folder somewhere and update CMAKE_MODULE_PATH appropriately.
How can one expect another user to have these files on his system?
It's your job to install whatever dependencies a package requires. Anything using modern CMake (bullet 1 listed above) should install the XXXConfig.cmake file as part of its installation. If a library is built by something other than CMake, you'd have to either hope for bullet #2, or find/write your own FindXXX.cmake file (bullet #3).
For your specific case, you might be better off with find_library, since your sample compilation line looks like it just needs to link.
I've just started working with CMake and I noticed that they have both a find_package and a find_library. And this confuses me. Can somebody explain the difference between a package and a library in the world of programming? Or, in the world of CMake?
Appreciate it, guys!
Imagine you want to use zlib in your project, you need to find the header file zlib.h, and the library libz.so (on Linux). You can use the low-level cmake commands find_path and find_library to find them, or you can use find_package(ZLIB). The later command will try to find out all what is necessary to use zlib. It can be extra macro definitions, or dependencies.
Update, more detail about find_package: when the CMake command find_package(SomeThing) is called, as in the documentation, there are two possible modes that cmake can run:
the module mode (that searches for a file FindSomeThing.cmake)
or the config mode (that searches for a file named SomeThingConfig.cmake)
For ZLIB, there is a module named FindZLIB, shipped with CMake itself (on my Linux machine that is the file /usr/share/cmake/Modules/FindZLIB.cmake). That module is a CMake script that uses the CMake API to search for ZLIB files in default locations, or ask the user for the location if it cannot be found automatically.
gcc (GCC) 4.7.2
cmake version 2.8.11
Hello,
I wondering if there is a way around the following issue. I have highlighted below:
SET(GW_SOURCE_FILES
module.c
module_imp.c
module_message.c
module_config.c
module_queue.c)
# Compiles the source files to create the shared library called dlg_gw.so
ADD_LIBRARY(dlg_gw SHARED ${GW_SOURCE_FILES})
# Link additional libraries to this
TARGET_LINK_LIBRARIES(dlg_gw gc srl ${APRUTIL})
# ISSUE: Now I want to create my executable using the same source files. module.c is where my 'void main(void)' is.
# However, I have some functions in there which will also be part of the library.
# However, this will recompile the same source files all over again. I don't really like that behaviour.
ADD_EXECUTABLE(sun_gw ${GW_SOURCE_FILES})
# After the executable is created, link the libraries with it.
TARGET_LINK_LIBRARIES(sun_gw ${APR} driver dlg_gw dlg_sip dlg_ss7 dlg_isdn)
I hope you can see the issue above, as I am compiling the same source files twice. Once to create the dlg_gw library. Then again to create the executable sun_gw.
I was thinking of taking out the 'void main(void)' and putting it in a new file called runtime.c and then doing the following:
ADD_EXECUTABLE(sun_gw runtime.c)
But the above require me to change some of the source code.
Many thanks for any other suggestions,
The "OBJECT" library type introduced in CMake 2.8.8 can be used to avoid repetitive build of same files.
See http://www.cmake.org/Wiki/CMake/Tutorials/Object_Library
I have a specific question which serves as context for a more general question.
There is a scientific package called LAMMPS, and it is usually used as an executable. However, it supports use as a "library". To try to do things right, I put it in /usr/local/lib/lammps. It contains a lammps/src/ directory, which has around 40 source files. Using the instructions provided, I compiled lammps as a .so file in lammps/src/liblammps_serial.so.
I also have separate code in "~/code/ljtube/". This uses cmake to try to find the library. Thus, I wrote a FindLAMMPS.txt so that I could use
FIND_PACKAGE (lammps)
in my CMakeLists. I modified the libtool config file to search in /usr/local/ successfully. I found that it searches in /usr/local/lib/ for a .so file and in /usr/local/include/ for a .h file. So I made a dynamic link to the .so file in /usr/local/lib/, and I copied the .h file from the lammps/src/ to /usr/local/include/.
CMake can now find those two files, but it cannot link to anything else in lammps/src/. It seems absurd to need to make a separate FIND_PACKAGE for each of the .h's I want to include (group.h, fix.h, force.h, pair.h, etc.). It also seems ridiculous to dump the whole package of .h files into the /usr/local/include/ directory. I will be using this code both locally and on a cluster, and possibly distributing it to other group members.
How can I make CMake find what I want to find without hard coding in the location of /usr/local/lib/lammps/src/? Phrased more generically, how should I manage large packages like these to make them easy to link to in the code I write, even if the original developer did not use the best conventions?
(As a side note, I am using a shared library because it seems like the right choice, but I'm not especially married to it. Should I be using a static library? Is there a way for CMake to find an already-compiled library relative to the current source directory, and might that be a better way to implement this? I know that I will be using LAMMPS in multiple projects, so having a local shared copy superficially seems to make the most sense.)
Normally a find_package call yields a variable specifying the path to the "includes" folder of the package. This would then be added in the caller's CMakeLists.txt via include_directories.
For example, to use find_package for boost, you could do:
find_package(Boost) # sets ${Boost_INCLUDE_DIRS} and ${Boost_LIBRARIES}
if(Boost_FOUND)
include_directories(${Boost_INCLUDE_DIRS})
add_executable(foo foo.cc)
target_link_libraries(foo ${Boost_LIBRARIES})
endif()
Regarding your side note, you could use find_library and/or find_path to find the library and its headers given a known location.
Both these commands can be invoked in such a way as to avoid searching in common locations, e.g. by setting PATHS to the known location and using NO_DEFAULT_PATH in the find commands.
Another alternative is for your projects to make use of the ExternalProject_Add function which is described in more detail in this article. From this article:
The ExternalProject_Add function makes it possible to say “download this project from the internet, run its configure step, build it and install it”
A downside to this approach is that each of your projects would end up with its own copy of the third party sources and lib.
I am new to OpenCL. I have written a vector addition code in OpenCL with help from Internet. I have included one header file i.e. CL/cl.h using #include.
I am using NVIDIA graphic card and the OpenCL implementation is NVIDIA_GPU_Computing_SDK. My OpenCL header files are residing at this path /opt/NVIDIA_GPU_Computing_SDK/OpenCL/common/inc. I can run OpenCL programs through linux terminal by adding this path when compiling my code. But now I want to write CMake file for this code. CMake files are working fine for C programs, but not OpenCL programs because of this Path problem. In terminal, I used to enter $cmake ., after this $make, it will search for a Makefile which is created by cmake, now my error is after entering command make
fatal error: CL/cl.h: No such file or directory!
Now tell me how can I include this header file into CMake file?
You will need to put these lines into CMakeLists.txt:
include_directories(/opt/NVIDIA_GPU_Computing_SDK/OpenCL/common/inc)
link_directories(/opt/NVIDIA_GPU_Computing_SDK/OpenCL/common/<lib or something similar>)
add_executable(yourexe src1.c ...)
target_link_libraries(yourexe OpenCL)
But beware that this is not portable, because OpenCL SDK can be somewhere else on another machine. The proper way to do this is to use FindOpenCL.cmake module.
Maybe you can use a CMake "find" script like:
http://gitorious.org/findopencl/findopencl/blobs/master/FindOpenCL.cmake
http://code.google.com/p/opencl-book-samples/source/browse/trunk/cmake/FindOpenCL.cmake?r=14
CMake file example from OpenCL Programming Guide Book: http://code.google.com/p/opencl-book-samples/source/browse/trunk/CMakeLists.txt?r=14
I was looking for FindOpenCL.cmake macro which would work well on Windows, OSX and Linux... I couldn't find any which did work well on every platform, so I wrote new one which I use in couple of projects (webcl-validator and opencl-testsuite).
https://github.com/elhigu/cmake-findopencl
Especially Windows support is improved in this one.
In Windows it checks if 64bit or 32bit lib should be used and it also tries to find libraries from according to environment variables set by Nvidia, Intel and AMD OpenCL SDKs.
It also tries to find .lib in Cygwin, which didn't work with other scripts I tried.