Building program with shared library

Hi folks!

I'm trying to build a (multi-file) sample program with a shared library for demonstration purposes. But unfortunately, I'm getting something wrong. Anybody here to help?

Code:

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$ make
gcc -Wall -g -o mylib.o -c mylib.c
gcc -Wall -g -o libmylib.so -shared mylib.o
gcc -Wall -g -o prog -L. -lmylib wrapLibraryFunc.c prog.c
wrapLibraryFunc.c:4:6: warning: ‘wrapLibraryFunc’ defined but not used [-Wunused-function]
    4 | void wrapLibraryFunc(char *message)
      |      ^~~~~~~~~~~~~~~
In file included from prog.c:1:
prog.h:1:13: warning: ‘wrapLibraryFunc’ used but never defined
    1 | static void wrapLibraryFunc(char *message);
      |            ^~~~~~~~~~~~~~~
/usr/bin/ld: /tmp/ccg3TTFt.o: in function `wrapLibraryFunc':
/home/user/src/cprogramming/wrapLibraryFunc.c:6: undefined reference to `printMessage'
/usr/bin/ld: /tmp/ccpTloxp.o: in function `main':
/home/user/src/cprogramming/prog.c:5: undefined reference to `wrapLibraryFunc'
collect2: error: ld returned 1 exit status
make: *** [Makefile:11: prog] Error 1

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The normal convention is that libraries go at the end of the command line.

Code:

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gcc -Wall -g -o prog wrapLibraryFunc.c prog.c  -L. -lmylib

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Ok, didn't know that.
But I'm still getting the same errors.

The problem is that you make wrapLibraryFunc static in the header file.
This causes it to not be seen outside of it's translation unit.
Get rid of the static.
Also, your char* parameters should really be const char *.

Gets me thinking of this.

Code:

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#include <stdio.h>

int main(int argc, const char **argv)

{   
    printf(" %s\n", argv[0]);
    return 0;
}

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