I use code::blocks to compile my static library. The output result is a libstatic.a file.
Now, how do I link to my library to use functions that were compiled?
(I tried to use #include "libstatic.a" but my project doesn't compile)
cc -o yourprog yourprog.c -lstatic
or
cc -o yourprog yourprog.c libstatic.a
You should #include "libstatic.h", i.e. use the appropriate header file in your code (that's why your code doesn't compile) and include the path to your libstatic.a in the linker options as one of your input libraries.
This webpage has some examples on linking to a static library, e.g.
gcc -I. -o jvct jvct.c libjvc.a
I had to set the library path in my makefile. For this case you could use:
gcc -o myapp main.c -L. -lstatic
gcc -I. -o jvct jvct.c libjvc.a
To link purely statically, use -static
cc -static yourprogram.c libstatic.a
Related
I am having issues linking a library (termbox) when compiling. I get the error:
make: *** No rule to make target `termbox.h', needed by `test.o'. Stop.
Makefile:
edit: test.o
gcc -Wall -o edit test.o
test.o: test.c termbox/src/termbox.h
gcc -Wall -c test.c -ltermbox/src
Include:
#include "termbox/src/termbox.h"
I have also tried using the compiled library but ran into similar issues. Do I have to use some sort of combination of specifying the header file and the location of the compiled library?
The directory of my termbox folder is in the same directory as test.c.
Thanks!
You have managed to compile and include the header file for the library, but you did not yet tell the compiler where the code (definitions) are - i.e. you did not tell it to link in the library yet.
You will need to do that next, this is done in a similar way to telling the linker what files to link, but with some extra syntax. It appears to be a static library (.a suffix) so you can link like this:
test.o: test.c termbox/src/termbox.h
gcc -Wall -c test.c -Itermbox/src -Lsrc -ltermbox
Where -L... specifies where libraries can be found and -l... specifies the library name to link to minus the lib prefix and the .a or .so suffix. Also note that order is important, so leave the library linkage at the end.
More on library linking order here
UPDATE
Sorry I added the linking to the wrong line! - here is the updated answer:
# The linker stage
edit: test.o
gcc -Wall -o edit test.o -Lsrc -ltermbox
# Compile stage
test.o: test.c termbox/src/termbox.h
gcc -Wall -c test.c -ltermbox/src
I use code::blocks to compile my static library. The output result is a libstatic.a file.
Now, how do I link to my library to use functions that were compiled?
(I tried to use #include "libstatic.a" but my project doesn't compile)
cc -o yourprog yourprog.c -lstatic
or
cc -o yourprog yourprog.c libstatic.a
You should #include "libstatic.h", i.e. use the appropriate header file in your code (that's why your code doesn't compile) and include the path to your libstatic.a in the linker options as one of your input libraries.
This webpage has some examples on linking to a static library, e.g.
gcc -I. -o jvct jvct.c libjvc.a
I had to set the library path in my makefile. For this case you could use:
gcc -o myapp main.c -L. -lstatic
gcc -I. -o jvct jvct.c libjvc.a
To link purely statically, use -static
cc -static yourprogram.c libstatic.a
I've just started to create my own C libraries to keep my commonly used functions tidy. However, I've hit a new problem and I struggled to find information on the best route to take.
I generate my library of two functions using the following:
gcc -I. -c -fpic rand_site.c
gcc -I. -c -fpic rand_spin.c
gcc -shared -o libstatphys.so rand_site.o rand_spin.o
Each of these source files contained a single function. I was hoping to create a third function for my library that uses the two functions above but I'm not sure how to use functions from within the same library.
Am I going about this the right way? What is the best practice for doing this?
Yes, you can.
Create a header file rand_site.h and put the declaration of the function defined in rand_site.c in it.
Create a header file rand_spin.h and put the declaration of the function defined in rand_spin.c in it.
Use #include to include the two .h files in the third file, say foo.c.
Then compile foo.c and add it to the library using:
gcc -I. -c -fpic foo.c
gcc -shared -o libstatphys.so rand_site.o rand_spin.o foo.o
If you would like to create a second shared library that has foo.o, you can use:
gcc -I. -c -fpic foo.c
gcc -shared -o libfoo.so foo.o -lstatphys
If you would like to create an executable using foo.o, you can use:
gcc -I. -c foo.c
gcc foo.o -lstatphys
I'm trying to create a hello world project for Linux dynamic libraries (.so files). So I have a file hello.c:
#include <stdio.h>
void hello()
{
printf("Hello world!\n");
}
How do I create a .so file that exports hello(), using gcc from the command line?
To generate a shared library you need first to compile your C code with the -fPIC (position independent code) flag.
gcc -c -fPIC hello.c -o hello.o
This will generate an object file (.o), now you take it and create the .so file:
gcc hello.o -shared -o libhello.so
EDIT: Suggestions from the comments:
You can use
gcc -shared -o libhello.so -fPIC hello.c
to do it in one step. – Jonathan Leffler
I also suggest to add -Wall to get all warnings, and -g to get debugging information, to your gcc commands. – Basile Starynkevitch
How to create a shared object file from a static library? I am using Cygwin.
Is the following syntax correct?
gcc -shared -o libexample.so libexample.a
gcc -shared -o libexample.so -Wl,--whole-archive libexample.a
Pay attention that often you'll want the objects combined in your .so to be compiled as PIC, something you don't often want for a static library.
It might not work but you can always try:
ar -x libexample.a
gcc -shared *.o -o libexample.so
If it complains about -fPIC, then it probably won't work.