RE: Dynamic Linking Library Problem Using GCC

["Martin York" <martin dot york at veritas dot com>]

Hi Cheok,

By specifying the argument:
-Wl,-soname,libmean.so.1

The executable will search for 'libmean.so.1' file at runtime to load.
But this does not exist. So you would also need to create a link from
your actual library to this name.

So in addition to the suggestion by 'Oliver' you will need to add
"ln -s libmean.so.1.0.1 libmean.so.1"


I am not sure why you are setting the 'soname' to a different name to
the resulting library, this seems dangerous to me (unless you can always
guarantee binary compatibility between all versions of libmean.so.1.X).

The general rule for building shared libs I use is:

g++ -shared -Wl,-soname,lib<LIBNAME>.so.<MAJ_VER>.<MIN_VER> -o
lib<LIBNAME>.so.<MAJ_VER>.<MIN_VER>  <FILES>
ln -s lib<LIBNAME>.so.<MAJ_VER>.<MIN_VER> lib<LIBNAME>.so.<MAJ_VER>
ln -s lib<LIBNAME>.so.<MAJ_VER> lib<LIBNAME>.so






-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On
Behalf Of Olivier Rochecouste
Sent: 13 December 2004 10:30
To: gcc-help@gcc.gnu.org
Subject: Re: Dynamic Linking Library Problem Using GCC

Hi Cheok,

I'm not an expert but I think you should make a symlink to your shared
library:

"ln -s libmean.so.1.0.1 libmean.so"

ld should be able to find the .so now

--
Olivier

> Hi,
> 
> I read through the tutorial
> http://www.adp-gmbh.ch/cpp/gcc/create_lib.html in buidling dynamic 
> library using gcc. It is interesting.
> However, after following the steps inside the tutorial, it doesn't 
> work in my system.
> 
> Here is the sequence of steps which I had performed:
> 
> [yccheok@localhost project]$ ls -al
> total 28
> drwxrwxr-x   2 yccheok yccheok  4096 Dec 13 01:16 .
> drwx------  65 yccheok yccheok 12288 Dec 13 00:58 ..
> -rw-rw-r--   1 yccheok yccheok    56 Dec 13 00:48
> calc_mean.c
> -rw-rw-r--   1 yccheok yccheok    29 Dec 13 00:48
> calc_mean.h
> -rw-rw-r--   1 yccheok yccheok   224 Dec 13 00:49
> main.c
> [yccheok@localhost project]$ gcc -c -fPIC calc_mean.c -o calc_mean.o 
> [yccheok@localhost project]$ gcc -shared
> -Wl,-soname,libmean.so.1 -o
> libmean.so.1.0.1  calc_mean.o
> [yccheok@localhost project]$ gcc main.c -o dynamically_linked -L. 
> -lmean
> /usr/bin/ld: cannot find -lmean
> collect2: ld returned 1 exit status
> [yccheok@localhost project]$ ls -al
> total 40
> drwxrwxr-x   2 yccheok yccheok  4096 Dec 13 01:17 .
> drwx------  65 yccheok yccheok 12288 Dec 13 00:58 ..
> -rw-rw-r--   1 yccheok yccheok    56 Dec 13 00:48
> calc_mean.c
> -rw-rw-r--   1 yccheok yccheok    29 Dec 13 00:48
> calc_mean.h
> -rw-rw-r--   1 yccheok yccheok   908 Dec 13 01:16
> calc_mean.o
> -rwxrwxr-x   1 yccheok yccheok  4349 Dec 13 01:16
> libmean.so.1.0.1
> -rw-rw-r--   1 yccheok yccheok   224 Dec 13 00:49
> main.c
> [yccheok@localhost project]$
> 
> Can you please advice on why the ld cannot find the mean library. Do I

> need to prior perform anything with ldconfig before i dynamic linked 
> my main application with the mean library?
> 
> Thank you!
> 
> -cheok
> 
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around 
> http://mail.yahoo.com
>