I am new to cmake so, sorry if this question is very basic.
I want to build my project as statically linked with each standard library it uses.
Like, in gcc if we want to link the standard system libraries(libc, libgcc etc) as static, we specify '-static' option at the time of compilation.(Like gcc main.c -static -o main).
How we can achieve the same in cmake?
I have read multiple threads to define a how to define a library, how to build, link(as static & shared). But that is all for a custom library, I need information for standard system libraries.
[Edit]
In my project, I am using yocto at the top and the cmake is been used underneath it. running directly cmake works fine, as the generated executable has no dependencies on any shared library, all the used libraries are linked statically. But compiling from yocto causing the issue. the executable generated from the yocto build shows the dependencies on several standard shared libraries.
How we can specify static linking of standard libraries in yocto cmake?
Thanks in advance.
Related
I recently made a small library in C, and I wanted to put it together with the standard libraries so I don't have to always copy the files for each new project.
Where do I have to put it so I can import it like the standard libraries?
Compiler : MinGW
OS: Windows
You need to create a library, but you don't necessarily need to put it in the same place as MinGW's standard libraries (in fact I think that's a bad idea).
It is better to put your own library/libraries in specific place and then use the -I compiler flag to tell the compiler where to find the header files (.h, .hpp, .hh) and the -L linker flag to tell the linker where to find the library archives (.a, .dll.a). If you have .dll files you should make sure they are in your PATH environment variable when you run your .exe or make sure the .dll files are copied in the same folder as your .exe.
If you use an IDE (e.g. Code::Blocks or Visual Studio Code) you can set these flags in the global IDE compiler/linker settings so you won't have to add the flags for each new project.
Then when building a project that uses your library you will need to add the -l flag with the library name to your linker flags, but without the lib prefix and without the extension (e.g. to use libmystuff.a/libmystuff.dll.a specify linker flag -lmystuff). The use of the -static flag will tell the linker to use the static library instead of the shared library if both are available.
I have created a minimal example library at https://github.com/brechtsanders/ci-test to illustrate on how to create a library that can be build both as static and shared (DLL) library on Windows, but the same code also compiles on
macOS and Linux.
If you don't use build tools like Make or CMake and want do the steps manually they would look like this for a static library:
gcc -c -o mystuff.o mystuff.c
ar cr libmystuff.a mystuff.c
To distribute the library in binary form you should distribute your header files (.h) and the library archive files (.a).
my c program calls:
hLibrary = dlopen("libPCBUSB.dylib", RTLD_LAZY);
and I seem to need this file in the directory when I run the executable after calling gcc main.c.
i.e. I run ./a.out and it all works as long as the dylib is in that directory.
In order to produce an executable with that dylib statically built in I've been trying all sorts of linking options but failing.
What is the correct way to compile my c program (in macOS Darwin not linux) to include this lib so the end user will not need it on their Mac?
Dynamic libraries (.dylib) can't be statically linked. If you have access to the source code for building the library, you can convert it to a static library and statically link against it in your app. If this is a 3rd-party binary-only library, you will need to ask the vendor for a static version of the library, and if that's not available, you will need to stick with linking it dynamically.
Note that dlopen() is not the only way to link against a dylib, you can also use -l, then you don't need to mess around with dlsym() etc. to get to the entry points. Either way requires shipping the library with your app of course.
I want to my make own library and have it use the same syntax as the standard C libraries as in
#include<mylib.h>
So that it looks like #include and some of the libraries that are included with C.
Can I make the library static as opposed to linking so that I can compile it in GCC without additional arguments, as if I were using another library like stdio.h or string.h?
This seems simple enough.
Develop the library (create as many source files as you need).
Build the source files into a shared library (.so) using a tool like CMAKE (which i strongly recommend).
Copy that library to your library path (i.e. /usr/lib)
Later on, all you have to do is import your lib: (i) in the source using #include<mylib.h>; (ii) when building (also using CMAKE) or using the flag (-lmylib) in the GCC compiler: gcc -lmylib myfiles.c -o myoutput.
In addition to #include "mylib.h", you need to add -lmylib command line to the compiler (more specifically linker) when using the library. I assume that the your library archive created through ar command is named as libmylib.a.
Usually, we do not write 'manually' build instructions, but we rely on tool that generates build chains. There are quite a lot of them, the most know are probably autotools and cmake (under Linux).
I would suggest you to have a look to cmake examples and/or documentation to get your code built.
There are quite a lot of differences between static and dynamic libs, and you will also need to package somehow your lib if you really want to use it like 'standard' lib (like libxml2, openssl, etc.)
A lot to say about it, but you should first have a look to 'how to build' your lib, and then see how to make it easy to use, IMHO.
I am looking for a program to create a C-library (i.e. to link and compile the files into one file) based on .h-files and .c-files that have the following structure (it is a FEC-library: www.openfec.org ). I am using Ubuntu. I want it to do this without manually specifying each files. I tried WAF, but got the error 'ERROR:root: error: No module named cflags'.
Here is (part of the) the structure:
fec
lib_advanced
ldpc_from_file
of_code_profile.h
of_ldpc_ff.h
...
lib_common
linear_binary_codes_utils
binary_matrix
it_decoding
ml_decoding
statistics
of_cb.h
of_debug.h
of_mem.c
of_mem.h
of_openfec_api.c
of_openfec_api.h
of_openfec_profile.h
of_types.h
Thanks!!
You have to use gcc to compile the C-files to objects files.
Then you have to use ar r and then ranlib to pack the objects into one .a library file.
C libraries on *nix systems (including all linux distros) are created with standards tools, this tools being a) a C compiler b) a linker b) the ar utility c) the ranlib utility.
The C compiler 99.9% of the time the GNU C compiler, while the linker ld, and the utilities ar and ranlib are part of the binutils package on gnu systems (99.9% of linux systems).
ar and ranlib are used to created static libraries, putting already compiled object files ( *.o files) in an archive file libsomething.a with ar and indexing the archive with ranlib.
The linker can be called inside the gcc compiler to create dynamic libraries with position independent code, again the already compiled files are archived on a special, this file has the .so extension for shared object.
Static Libraries are used for speed and self-containment, they produce big executables which contain all their dependencies inside the final executable. If a single library of many changes, to update it you'll have to recompiled everything.
Dynamic libraries are compiled and linked separately of the executables, they can be used simultaneously by multiple executables, if one library is updated, you just need to recompile a single library and not every executable which depends on it.
The use of this tools are universal and standard procedure, they can vary by few details from *nix systems to *nix system, but on linux you essentially always use the GCC and Binutils packages. Extra build utilities on the form of make, cmake, autotools, etc exist to help on the process, but the basic tools are always used.
Generally on the most basic level you write a Makefile script which is interpreted by the make utility. And depending on your commands it can make one or both kinds of libraries, install the library and executables, uninstall them, clean up, etc
For more information :
http://www.yolinux.com/TUTORIALS/LibraryArchives-StaticAndDynamic.html
http://www.dwheeler.com/program-library/Program-Library-HOWTO/
I'm currently trying to link a CXX library that I've written to a VTK, a CMake made library - to end up creating a shared library that has my code's functionality and can resolve the symbols from VTK. I need the end result to be shared because I'd need to call the library up at runtime in Java.
It sounds like you need to use target_link_libraries, so a minimal CMake block might look like,
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_library(mylib SHARED sourcefile.cxx sourcefile2.cxx)
target_link_libraries(mylib vtkRendering)
This would add a shared library called mylib (libmylib.so on Linux), that links to vtkRendering (multiple libraries could be added here). Check out 'cmake --help-commands' for a full list of CMake commands.