R. Brock Lynn wrote:
>
> I've recently acquired a copy of the new "Linux Application Development" by
> Michael K. Johnson and Erik W. Troan.
>
> In it, it describes how to create and use shared libraries. But when I follow
> the instructions. It doesn't work.
>
> Here is the example:
>
> `libhello.c'
> -------------------------------------------------------------------------------
> #include <stdio.h>
> void print_hello(void){
> printf("Hello, shared library.\n");
> }
> -------------------------------------------------------------------------------
>
> `libhello.h' (this file was not included, but below is a best guess)
> -------------------------------------------------------------------------------
> void print_hello(void);
> -------------------------------------------------------------------------------
>
> `usehello.c'
> -------------------------------------------------------------------------------
> #include "libhello.h"
> int main(void){
> print_hello();
> return 0;
> }
> -------------------------------------------------------------------------------
>
> Compile and Link instructions:
>
> gcc -fPIC -Wall -g -c libhello.c
>
> gcc -g -shared -Wl,-soname,libhello.so.0 -o libhello.so.0.0 libhello.o -lc
>
> ln -sf libhello.so.0.0 libhello.so.0
>
> ln -sf libhello.so.0 libhello.so
>
> gcc -Wall -g -c usehello.c -o usehello.o
>
> gcc -g -o usehello usehello.o -L. -lhello
>
> Then run with:
>
> LD_LIBRARY_PATH='pwd' ./usehello
>
> But I get this error:
>
> ./usehello: can't load library 'libhello.so.0'
>
> Any suggestions?
yes! I changed those compile instructions a little, and then it works.
(my gcc does not recognize a 'soname' option. does yours?)
try this: (it works)
gcc -fPIC -c libhello.c // libhello.o
gcc -shared libhello.o -o libhello.so // libhello.so
gcc -c usehello.c // usehello.o
gcc usehello.o -o usehello -L . -lhello // dynamically linked
usehello
setenv LD_LIBRARY_PATH `pwd` // (I use tcsh)
!!! note the grave quotes: `` not ''
(you could also type setenv LD_LIBRARY_PATH /the/correct/path instead )
check by doing echo $LD_LIBRARY_PATH
it should say something like LD_LIBRARY_PATH=/where/your/libhello.so/is
otherwise libhello.so cannot be found.
good luck!
Christoph
