CODEWITHSUNDEEP
clinuxgcc
Petr Skocik
Petr Skocik

Reputation: 60147

Linking a shared library from a different place than its intended final location

Suppose I have a main.lo which I'd like to link against library foo.so. The linker should always look for foo.so at /foo/bar/lib.so (fixed path, no search), but I only have lib.so in my home directory and not in /foo/bar/, which is a protected directory I can't write to myself.

Is it possible to link the lib like this?

Edit: Below is a simple example using /tmp instead of /foo/bar. Can you make it work by modifying the build script?

main.c

void foo();
int main(){
  foo();
  return 0;
}

foo.c (multiple-file libraries are overrated)

#include <stdio.h>

void foo(){
  puts("foo");
}

build.sh

#!/bin/sh
set -x
gcc -c -fPIC main.c -o main.lo
gcc -c -fPIC foo.c -o foo.lo
gcc -shared -o foo.so foo.lo

gcc -o pwd main.lo "$PWD/foo.so"
rm -f /tmp/foo.so

#? Link into dest, against /tmp/foo.so but use "$PWD/foo.so"


cp -a foo.so /tmp/foo.so

echo pwd:
./pwd   #this works
echo dest:
./dest

Upvotes: 2

Views: 276

Answers (1)

Some programmer dude
Some programmer dude

Reputation: 409432

You need two options to make it work:

First you need to use the -L option to tell the linker where the library is actually located at the moment.

Then you need to use the -rpath linker option to tell where the final location will be. Unfortunately this is a linker-specific option which means you need to use the -Wl option to the GCC frontend program.

So the command should look something like

$ gcc object.o files.o -o target \
    -L/current/path/to/library -Wl,-rpath,/final/path/to/library -llibrary

Note that the two paths can of course be the same.

Upvotes: 3

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