linker problem

svenveer · #1 14-Oct-2005, 12:00

Hi, I'm using g++ from eclipse. I'm trying to compile the following:

CPP / C++ / C Code:

#include <glib.h>
#include <libgnomevfs/gnome-vfs-init.h>
#include <libgnome/gnome-url.h>

int main(void){
  const char* filePathStr = "file://home/sven/fotos/DSC00013.JPG";
  GError *error = NULL;
  gnome_url_show(filePathStr, &error);
}

The problem is that the linker cannot find the libraries:

Code:

Building file: ../testgnome.c
Invoking: GCC C Compiler
gcc -I/opt/gnome/include/glib-2.0 -I/opt/gnome/include/gnome-vfs-2.0 -I/opt/gnome/include/libgnome-2.0 -I/opt/gnome/lib/glib-2.0/include -O0 -g3 -Wall -c -fmessage-length=0 -otestgnome.o ../testgnome.c
Finished building: ../testgnome.c
 
Building target: c_gnome
Invoking: GCC C Linker
gcc -L/opt/gnome/lib -oc_gnome ./testgnome.o -llibgnome-2
/usr/lib/gcc-lib/i586-suse-linux/3.3.4/../../../../i586-suse-linux/bin/ld: cannot find -llibgnome-2
collect2: ld returned 1 exit status
make: *** [c_gnome] Error 1
make: Target `all' not remade because of errors.
Build complete for project c_gnome
Building file: ../testgnome.c
Invoking: GCC C Compiler
gcc -I/opt/gnome/include/glib-2.0 -I/opt/gnome/include/gnome-vfs-2.0 -I/opt/gnome/include/libgnome-2.0 -I/opt/gnome/lib/glib-2.0/include -O0 -g3 -Wall -c -fmessage-length=0 -otestgnome.o ../testgnome.c
Finished building: ../testgnome.c

the libgnome-2 library really exists in /opt/gnome/lib with .a .la .so .so.0 and .so.0.601.0. They are owned by root and have rx permissions for others. What am I missing here.

O, by the way, I'm using suse9.2

monalin · #2 14-Oct-2005, 13:53

i'm no expert coder or heck i dont even pretend to know anything lol. But since nobody's posted anything i'll give my 2 cents.

I cant help you very much cause i'm not really sure what your trying to do but i know that most additional library's have to be added in the Linker Properties box.

I'm not useing the same compiler as you but for me its under Project -> 'PROJECT NAME' Properties -> Linker -> General -> Additional Library Directories

maybe that will help you find the problem. again i could be way off sorry if i am.

davekw7x · #3 14-Oct-2005, 14:42

Quote:

Originally Posted by svenveer

Hi, I'm using g++ from eclipse.

The problem is that the linker cannot find the libraries:

Building target: c_gnome
Invoking: GCC C Linker
gcc -L/opt/gnome/lib -oc_gnome ./testgnome.o -llibgnome-2
/usr/lib/gcc-lib/i586-suse-linux/3.3.4/../../../../i586-suse-linux/bin/ld: cannot find -llibgnome-2

I don't have suse or eclipse to test the results, but I'll take a wild stab at it.

I will point out that the legacy of C compiler/linkers command line usage is kind of strange.

For example, if the library name is libm.a, the command line to include this would be something like

Quote:

gcc -lm x.c

If you have a library named libiberty.a, you would use

Quote:

gcc -liberty x.c

See the pattern? So, if your library is named libgnome-2.a, your command line wouldn't have "llibgnome-2", it would have this:

Quote:

gcc ...... -lgnome-2 .....

Let us know if it makes a difference.

Note that if you are sure that the library name is OK, you can make sure that the tools get to the right directories by using "-v" in the command line for gcc. The "verbose" output of the compiler tells us where it is looking.

Regards,

Dave

svenveer · #4 17-Oct-2005, 10:14

Thanks Dave that did the trick. Returning to c/c++ after 8 years of java ;-)

So, as a rule, libs named libxyz are 'known' to the linker as xyz.

Sven

davekw7x · #5 17-Oct-2005, 11:06

Quote:

Originally Posted by svenveer

Thanks Dave that did the trick. Returning to c/c++ after 8 years of java ;-)

So, as a rule, libs named libxyz are 'known' to the linker as xyz.

Sven

This is in keeping with the traditional UNIX philosophy of minimizing keystrokes, especially on command lines.

You know, "cp" for copy, "rm" for remove, "mv" for move, etc., so "gcc -lm z.c" to link in libm.a

Note that while developing and testing, I usually name my programs z.c (even in Windows) instead something like "theBigTestProgramForSocketsProgramming.c", so you can see that I have bought into it.

Regards,

Dave

svenveer · #6 17-Oct-2005, 11:27

Quote:

Originally Posted by davekw7x

This is in keeping with the traditional UNIX philosophy of minimizing keystrokes, especially on command lines.

You know, "cp" for copy, "rm" for remove, "mv" for move, etc., so "gcc -lm z.c" to link in libm.a

I guess I've used Eclipse too much to really remember that

Before that it was Borland C++ Builder. I guess I need to be reeducated

I guess however that my boss prefers "TheReallyReallyLongNameForTheApplicationHeSoldThe Client" instead of just "z"

I must say I Like the "z" though

davekw7x · #7 17-Oct-2005, 13:38

Quote:

Originally Posted by svenveer

I guess I've used Eclipse too much to really remember that

Before that it was Borland C++ Builder. I guess I need to be reeducated

I guess however that my boss prefers "TheReallyReallyLongNameForTheApplicationHeSoldThe Client" instead of just "z"

I must say I Like the "z" though

That's what Makefiles are for. Enter the stuff once, then just enter make.

(Or if you are really lazy, put alias 'm=make' in your ~/.bashrc, then you only enter m.)

Regards,

Dave

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