How to compile library on C using GCC?
c, compilation, gcc, include, libraries
Solution
First, always take the habit to compile with `-Wall` (and perhaps even also `-Wextra` to get even more warnings) option to `gcc`; it gives you almost all warnings, and you should improve your code till no warnings are given.
Then you often want to be able to debug your code, so also pass `-g` to `gcc`. Once you are confident with your code you could ask `gcc` to produce optimized machine code with `-O2`. Learn to use the `gdb` debugger.
So compile your first library, assuming its source files `first1.c` and `first2.c` are in `FirstLib/` directory, with e.g.
cd FirstLib/
gcc -Wall -g -c first1.c -o first1.o
gcc -Wall -g -c first2.c -o first2.o
At this point, you should use a `Makefile` and learn how to use `make`, in particular because you want to get your `libfirst.a` with
ar ruv libfirst.a first1.o first2.o
ranlib libfirst.a
Then you can pass `-L../FirstLib -lfirst` as the last options to the `gcc` command compiling and linking your program using your `libfirst.a`
Then compile your second library by having your `Makefile` in directory `SecondLib/` which very probably should contain
# in SecondLib/Makefile
CC=gcc
CFLAGS= -I../FirstLib/ -Wall -g
## add your other stuff for make
etc etc. You really want to learn how to use `make` and write your own `Makefile`-s so take time to read the GNU make documentation.
You may want to pass `-H` to `gcc` to have it tell you all the included files, and you may want to also use remake (in addition & replacement of `make`) to debug your more complex `Makefile`-s (notably by running `remake -x`). Here is an example of `Makefile`; you'll find many others!
Read also the Program Library Howto.
Problem
I made a library with the files `pila.h` and `pila.c`. I compile the file `pila.c` with `gcc pila.c -c` and this library works fine. I have tested it. Then I made another library. This library has the files `pila_funciones_extra.h` and `pila_funciones_extra.c`. In this library I need to include the first library. In the file `pila_funciones_extra.h` I put the next line to include it: ``` #include "pila.h" ``` and in the file `pila_funciones_extra.c` I put the next line: ``` #include "pila_funciones_extra.h" ``` as it has to be. But when I try to compile the file `pila_funciones_extra.c` the compiler doensn't recognize the inclusion of the library `pila`. It says that the functions, structures, constants and macros that are defined in the library `pila` haven't been defined. I tried to compile it with `gcc pila_funciones_extra.c -c` and `gcc pila_funciones_extra.c -c pila.o` but it doesn't work. I made sure that all the files are in the same folder. I'm working on Ubuntu. Can anyone tell me the right way to compile it?