I’m cross compiling my C projects using Eclipse CDT/CodeSourcery Lite on Ubuntu v12.10.
In Eclipse CDT, I have these three C projects:
exeTop // executable that uses functions defined in libmiddle.a
libmiddle.a // static library that uses functions defined in libbottom.a
libbottom.a // standalone static library that doesn’t
depend on any other libraries
In order to build libmiddle.a, I have to copy libbottom.a into libmiddle’s project folder (see instructions here), which makes sense as libmiddle.a depends on libbottom.a.
However when building exeTop, I not only have to link to libmiddle.a but to libbottom.a (which libmiddle.a has already linked to).
Q1. Why is it required to link to libbottom.a from exeTop?
Q2. Are there any compiler or linker options I can use so that I can just link to libmiddle.a from exeTop?
You say "In order to build libmiddle.a, I have to link to libbottom.a, which makes sense as libmiddle.a depends on libbottom.a." I do not think this is the case at all. In fact, libmiddle.a can't really link against libbottom.a, because that's not how static libraries work on Linux. Static libraries are just "archives" of object files, and don't have a feature that makes them depend on other static libraries. Nor is it typical to stuff a static dependency into a static library itself.
For some more details, see [UNIX] : Do I need to add all libraries in my project's makefile, that are used from a library, used in my project?
Related
I have a C static library (foo.a) built for arm64 target (aarch64-unknown-linux-musl). I need to call some C functions in that library from my Rust project.
How do I link to that pre-existing library (foo.a) without building it?
I defined extern C functions for my library so technically, if I can link to it, I should be able to use it from Rust code?
extern "C" {
pub fn somefunc();
}
The problem I run into is that Cargo rust build wants to use the default toolchain (stable-x86_64-unknown-linux-gnu) and I don't have my library compiled for that target. Can I customize Cargo build to not require stable-x86_64-unknown-linux-gnuand simply link against existing pre-compiled library for another target platform?
I tried modifying rust project settings to change default rustup default <toolchain>; but cargo build did not recognize the target aarch64-unknown-linux-musl. Then I tried to change build dependency to specify foo.a as static lib for my target.
[build-dependencies]
foo = { artifact = "staticlib", version = "1.0", target = "aarch64-unknown-linux-musl" }
I'm building a project that uses cmake.
The project uses three shared libraries .so files.
In the CMakeLists.txt file I've added the these lines which link the shared libraries to the executable.
project (lwm2mclient)
LINK_DIRECTORIES(/home/mraa-master-built/build/src)
LINK_DIRECTORIES(/home/libi2capi)
LINK_DIRECTORIES(/home/libtca6424a)
target_link_libraries (lwm2mclient libmraa.so m libi2capi.so libtca6424a.so)
However, one of the shared libraries libtca6424a.sodepends on libi2capi.so i.e. it uses methods that are defined in it.
So when I'm building the cmake project I get an error like this saying that the .so file cannot find the method which is defined in the other .so file libtca6424a.so.
Could somebody suggest a solution?
/../../lib/libtca6424a.so: undefined reference to `i2c_write_byte_data'
Please try
target_link_libraries (-Wl,--start-group lwm2mclient libmraa.so m libi2capi.so libtca6424a.so -Wl,--end-group)
or change the order of the libraries
I have a c language program that has the following structure:
src/main/c/main.c
src/main/headers/main.h
src/module_1/c/module_1.h
src/module_1/headers/module_1.h
...
src/modulen/c/module_n.c
src/module/headers/module_n.h
In the gradle script I have defined:
components {
module_1(NativeLibrarySpec)
...
module_n(NativeLibrarySpec)
main(NativeExecutableSpec){
sources{
c.lib library: "module_1", linkage: "static"
...
c.lib library: "module_n", linkage: "static"
}
The reason of using this structure is to facilitate creating unit tests for each module separately.
The problem comes with the inclusion of the .h files from the modules in the main or in other modules (there are some dependencies between them). I haven't found a way to make the headers of a module available to other modules. I would actually like to make them all "global" to the project (that is, automatically added to the source set for any module).
Thanks in advance
I do not know gradle but may give you some general advise.
I haven't found a way to make the headers of a module available to other modules.
You could make a central directory (repository) for all .h files of your project, for example src/include. The header files of each module can be placed there (in the version of the curent baseline).
I would actually like to make them all "global" to the project (that is, automatically added to the source set for any module).
The above repository can support that. However, including a header in a source file is a manual task. It is also wise not to include all headers into a source file; it may only need a few.
I am using the LPCXpresso IDE to program my microcontroller to use the libjpeg library for a particular application. However, I cannot seem to get the LPCXpresso IDE to recognize libjpeg. The way I see it, there are two options:
1) Take the jpeglib.a file, include it as an external library, and then attempt to import jpeglib.h. I have tried this, at the IDE still does not recognize jpeglib.h.
2) Create a new static library from the libjpeg source code. Is this my only option? It seems a bit excessive.
Any tips regarding adding/linking external libraries in LPCXpresso would be greatly appreciated. Thanks!
You can easily add a library to Eclipse/LPCXpresso by creating a new project (not a C project or a LPCXpresso project but a 'normal' project) by clicking File->New->Project. Name is as you wish, let's say 'JPEG'. Add your library file to it under the folder 'lib' (you have to create the folder first). Call the library file 'libJPEG.a'. Also include the header file under the folder 'inc'. It is not mandatory to create these folders by the way, but it makes it all more organised.
The edit the properties of the project that's needs to include the header and library. Right click the project and choose properties. Go to C/C++ Build->Settings->MCU C compiler->Includes and add the include path of the inc folder of the library project. The go to C/C++ Build->Settings->MCU Linker->Libraries and add the library file WITHOUT the lib in front of the file name, hence just JPEG. Also add the library search path below (point to the lib folder).
That's all!
Ok, so here's my question:
I have a working DUB project which produces an application. I decided I also wanted a "library" configuration in my dub.json file:
"configurations": [
{
"name": "application",
"targetType": "executable"
},
{
"name": "library",
"targetType": "library",
}
],
So, now when I build the project using dub build --config=library, it produces a libXXXX.a file in the same directory.
So far, so good.
I tried using this library (actually a tiny test-function marked as extern "C" from a test C app).
So, I compile my C app using gcc -c ctest.c and then link them all together like dmd libMYLIBRARY.a ctest.o.
Now, here is the problem:
In this last step, the linker complains that many symbols are missing - all coming from external dependencies (2 object files and several .a libraries) that would normally be linked when building the project as an application.
So, the question is... how do I solve this?
I mean... Should I just link my test C app against ALL of the original dependencies (this would not make the library very portable admittedly), or is there any way around it, so that anybody could use my library, only by linking against my libXXXXX.a file?
Should I just link my test C app against ALL of the original dependencies (this would not make the library very portable admittedly),
This is the "technically correct" answer. The reason for that is because, otherwise, if the C app wanted to use another D library which had among its dependencies some package that's also a dependency in your library, and if it were linked in the same way (including all of its dependencies in its static library file), this dependency would then occur twice in the linker inputs. Even if you told the linker to discard one copy, there can be problems due to the dependency being of separate incompatible versions, etc. (Note that there is an ongoing D SAOC project to handle this.)
If you were to assume that the only D library the C program will use is your Dub package, then you could conceivably create a static library which includes all dependencies, though it would probably need to include the D standard library and runtime as well.