I am trying to import a Makefile based Cortex-M3 project into SEGGER Embedded Studio (SEGGER Embedded Studio for ARM
Release 5.10b Build 2020091601.43513).
My project compiles and links however the binary size is way too large compared to the original project. The resulting executable works but just takes too much FLASH space.
Comparing the map files I see that all symbols and contents of a certain library (ELF .a file dropped into the source tree) are linked into my binary with the SEGGER linker.
I cannot rebuild the .a file as it is supplied by a 3rd party in binary form.
I tried
placing the .a file in the source hierarchy like a source file
referring to the file in the linker configuration as an "additional input file"
How can I force the SEGGER linker from my solution to strip unused symbols?
"From SEGGER product manual: Eliminates all unused code and data for a minimum-size image."
Related
I've seen from resources that .a files are static library files for WINDOWS Systems, and that .lib files are the equivalent but for UNIX systems. I'm beginning to try to import libraries in projects and saw that for SDL2 specifically, there are .a files that I include with my linking commands with minGW is there something under the hood that is going on for these files to be read and used on a Windows machine?
I've linkedthese successfully (and not-so-successfully a few hours ago),but this bugged me so I wanted to ask you all :)
On Windows machines using MinGW, .a files (also known as static library files) are handled by the linker (ld.exe) during the linking stage of the compilation process. The linker takes the object files (.o) generated by the compiler (gcc.exe) and combines them with the code and data stored in the .a files to create a single executable file. The linker also resolves any symbol references between the object files and the library code and data.
I have Atmel Studio installed on my system, but when I want to use for example time.h of the stdio, it tells me the library does not exist!
So I downloaded this library:
http://download.savannah.gnu.org/releases/avr-libc/
Now, how can I include the whole library in my project?
After extracting, there are individual .h files and .c files that I can add in libc and include folders, but I'd like to add them all to my project (at least all of stdio, time, string...).
Thanks
I am able to successfully cross-compile a binary file that can run on an ARM system such as Rasberry Pi. Without linking to a third-party library, normal C++ code runs on the device successfully (I.E. cout << "Hello World!" << endl;).
The issue I'm running into is that when I run the executable after it's been linked against a third-party library, I get the standard UNIX error "No such file or directory." when the binary tries to access the shared object file. I have the file it's looking for copied into the usr/lib folder, the usr/local/lib folder, and the folder where the executable is sitting itself.
Also, I went and added a good value to LD_LIBRARY_PATH so the runtime linker can search at these locations. My guess is that the "system" maybe hiding these files from the executable?
And to add more information, I ran the readelf command on the binary and the shared object file and it gives me the proper descriptions of the file. It tells me that the binary file is a 32-bit file and requires this shared object library file that I mentioned it cannot find. Even during link time in the build phase, I add the following linker command -Wl,-rpath, to set the location of where to look for the shared object file. Please note I'm compiling on a Macintosh Machine, and not on the Rasberry Pi itself. Hence cross-compiling.
I have a feeling it's a setting, because the object file is visible/valid in multiple locations. If anyone has experienced this before, please any advice is appreciated. Thanks in advance.
I actually figured out the problem recently.
The problem was that I was using Eclipse. The third party library files I was using were named in the format "libSHAREDFILENAME.so". Eclipse doesn't like that very much when setting up which libraries to use in the IDE. It expects you to strip off the "lib" and the ".so" portion from the file name. So a file named "libSHAREDOBJECT.so" should be referenced as "SHAREDOBJECT" in Eclipse. It doesn't like the "lib" prefix or the ".so" suffix.
I have seen in driver libraries these three files. How are the three files related, what is the order in which the files are compiled and what is the content of each file? In addition to this I have also seen .a files are they same as .lib?
.lib and .dll files are both containers of executables of a Windows library (.o or .obj files), with the former (.lib) containing stuff (functions, definitions, etc) that you have to link statically to the executable file of your project. The latter (.dll) is either already present in your system or you put it into your system, and it is dynamically linked to the executable file of your project.
For Unix/Linux systems, the file-extensions are .a and .so respectively (that is, .a instead of .lib, and .so instead of .dll).
In all cases, when compiling your project you must #include one or more of the .h files provided to you by the library you are using (they are called header files), because that's where the stuff inside the executables of the library get defined.
EDIT
The main advantage of a statically linked library is that it is self-contained (no external dependencies) but it increases the size of your own executable file. The main disadvantage is that future versions must be re-compiled and re-distributed.
For dynamically linked libraries, we re-distribute just the updated library executables. The main disadvantage is that our program relies on the library being already installed on the customer's system.
I'm currently trying to port a C application to AIX and am getting confused. What are .a and .so files and how are they used when building/running an application?
Archive libraries (.a) are statically linked i.e when you compile your program with -c option in gcc. So, if there's any change in library, you need to compile and build your code again.
The advantage of .so (shared object) over .a library is that they are linked during the runtime i.e. after creation of your .o file -o option in gcc. So, if there's any change in .so file, you don't need to recompile your main program.
But make sure that your main program is linked to the new .so file with ln command.
This will help you to build the .so files.
http://www.yolinux.com/TUTORIALS/LibraryArchives-StaticAndDynamic.html
.a are static libraries. If you use code stored inside them, it's taken from them and embedded into your own binary. In Visual Studio, these would be .lib files.
.so are dynamic libraries. If you use code stored inside them, it's not taken and embedded into your own binary. Instead it's just referenced, so the binary will depend on them and the code from the so file is added/loaded at runtime. In Visual Studio/Windows these would be .dll files (with small .lib files containing linking information).
.a files are usually libraries which get statically linked (or more accurately archives), and
.so are dynamically linked libraries.
To do a port you will need the source code that was compiled to make them, or equivalent files on your AIX machine.
They are used in the linking stage. .a files are statically linked, and .so files are sort-of linked, so that the library is needed whenever you run the exe.
You can find where they are stored by looking at any of the lib directories... /usr/lib and /lib have most of them, and there is also the LIBRARY_PATH environment variable.
Wikipedia is a decent source for this info.
To learn about static library files like .a read Static libarary
To learn about shared library files like .so read Library_(computing)#Shared_libraries On this page, there is also useful info in the File naming section.