CODEWITHSUNDEEP
c++cmakefile
Pradheep
Pradheep

Reputation: 3819

Makefile Linking with shared library fails

I was trying to write a shared library and trying 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 the LD_LIBRARY_PATH

echo $LD_LIBRARY_PATH
/home/pradheep/myexploration/mystring

Output of my libmystring.so

 000004ca T mystrncpy
 0000045c T mystrcpy

What am i missing ?

Solution:

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

Upvotes: 6

Views: 3708

Answers (1)

Dayal rai
Dayal rai

Reputation: 6606

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

Upvotes: 5

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