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.
Related
I want to run the example project which is available for free from this link. It is a simple FFT library and needs no compiler. In it, there is an example c file with its required header files and .c files.
When I try to run it in Vivado SDK I get errors of multiple definitions of fft and ifft. How can I run this example inside SDK?
What I had done is created an empty application project and then imported all these files inside src folder and then selected build the project option but didn't succeed in building and running the project.
I guess, looking at the ufft.zip archive, that you've tried to link files issued form the compilation of fft-dit.c and fft-dif.c.
Both files define ftt functions using differents method (see README).
You have to choose betwen using ftt-dif.c or ftt-dit.c, not both.
This is the same for itt-dif.c and itt-dit.c, choose one, not both.
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 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!
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?
I'm trying to use the SkypeKit SDK to create an Objective-C++ project using Xcode 4. I have two compiled libraries from SkypeKit, libskypekit_cyassl_lib.a and libskypekit_cppwrapper_2_lib.a, which I need to be able to use so as to access the Skype API.
I've added in both .a files under 'Linked Frameworks and Libraries' and added -all_load -ObjC -lstdc++ to the 'Other Linker Flags', and that builds okay, but as soon as I try to use any of the methods in those libraries, building fails.
Any help would be greatly appreciated, thank you!
You can call C++ code from Objective-C++, which means that your files should have the .mm extension instead of .m
I assume that this could be the issue, but since you did not specify the errors you get it is just a guess. Specifically, if you call C++ code from a .m file you get compilation errors.
Another possible cause is forgetting to import the header files of the library. For the import to be successful, you also have to add the directory where the headers are to your project "header search path".
If this does not help, please post the error message.