Pin a Makefile with a shared library

Question

I tried to write a shared library and try to link it to form the final executable.

Makefile

mystring.out:main.c libmystring.so gcc -I. -L/home/pradheep/myexploration/mystring/ -lmystring main.c -o mystring.out libmystring.so:mystring.o gcc -shared -Wl,-soname,libmystring.so -o libmystring.so mystring.o libmystring.a:mystring.o ar -r libmystring.a mystring.o mystring.o:mystring.h mystring.c gcc -Wall -g -c -fPIC -I. mystring.c clean: rm *.o rm *.a rm *.so rm *.out 

Here is the error message:

  gcc -I. -L/home/pradheep/myexploration/mystring/ -lmystring main.c -o mystring.out /tmp/ccS9UDPS.o: In function `main': main.c:(.text+0x2d): undefined reference to `mystrcpy' main.c:(.text+0x5a): undefined reference to `mystrncpy' main.c:(.text+0x87): undefined reference to `mystrncpy' main.c:(.text+0xa4): undefined reference to `mystrlen' collect2: ld returned 1 exit status make: *** [mystring.out] Error 1 

I have already exported LD_LIBRARY_PATH

 echo $LD_LIBRARY_PATH /home/pradheep/myexploration/mystring 

The output of my libmystring.so

  000004ca T mystrncpy 0000045c T mystrcpy 

What am I missing?

Decision:

The problem was with the use of the -l library. It should be used after the source file and the correct order as indicated by Dayal rai, gcc -I. -L / home / pradheep / myexploration / mystring / main.c -lmystring -o mystring.out and hurray it works.

Answer 1

The traditional behavior of linkers is to look for external functions from left to right in the libraries specified on the command line. This means that the library containing the function definition must appear after any source files or object files that use it.