Simple libnotify "hello world" program fails to compile on Ubuntu 20.04 with linker error-CodePudding

I'm probably missing something very basic here but for some reason I'm unable to successfully link against libnotify on my Ubuntu 20.04 system, even though everything is installed correctly and pkg-cfg (IMHO) returns the right options... any ideas ?

user@home:~/jabrac$ ldconfig -v | grep notify                                                                                                                                                                                                                                                                      
        libnotify.so.4 -> libnotify.so.4.0.0

user@home:~/jabrac$ dpkg -L libnotify-dev 
/.
/usr
/usr/include
/usr/include/libnotify
/usr/include/libnotify/notification.h
/usr/include/libnotify/notify-enum-types.h
/usr/include/libnotify/notify-features.h
/usr/include/libnotify/notify.h
/usr/lib
/usr/lib/x86_64-linux-gnu
/usr/lib/x86_64-linux-gnu/pkgconfig
/usr/lib/x86_64-linux-gnu/pkgconfig/libnotify.pc
/usr/share
/usr/share/doc
/usr/share/doc/libnotify-dev
/usr/share/doc/libnotify-dev/copyright
/usr/share/gir-1.0
/usr/share/gir-1.0/Notify-0.7.gir
/usr/lib/x86_64-linux-gnu/libnotify.so
/usr/share/doc/libnotify-dev/changelog.Debian.gz
user@home:~/jabrac$ ls -l /usr/lib/x86_64-linux-gnu/libnotify.so*
lrwxrwxrwx 1 root root    14 Mär 20  2020 /usr/lib/x86_64-linux-gnu/libnotify.so -> libnotify.so.4
lrwxrwxrwx 1 root root    18 Mär 20  2020 /usr/lib/x86_64-linux-gnu/libnotify.so.4 -> libnotify.so.4.0.0
-rw-r--r-- 1 root root 38984 Mär 20  2020 /usr/lib/x86_64-linux-gnu/libnotify.so.4.0.0

user@home:~/jabrac$ cat hello_world.c 
#include <libnotify/notify.h>
#include <stdio.h>

int main(int argc, char * argv[] ) 
{
    notify_init("Sample");
    NotifyNotification* n = notify_notification_new ("Hello world", 
                                 "some message text... bla bla",
                                  0);
    notify_notification_set_timeout(n, 10000); // 10 seconds

    if (!notify_notification_show(n, 0)) 
    {
        printf("show has failed\n");
        return -1;
    }
    return 0;
}
user@home:~/jabrac$ gcc `pkg-config --cflags --libs libnotify` hello_world.c 
/usr/bin/ld: /tmp/cckbaX1n.o: in function `main':
hello_world.c:(.text 0x1b): undefined reference to `notify_init'
/usr/bin/ld: hello_world.c:(.text 0x33): undefined reference to `notify_notification_new'
/usr/bin/ld: hello_world.c:(.text 0x48): undefined reference to `notify_notification_set_timeout'
/usr/bin/ld: hello_world.c:(.text 0x59): undefined reference to `notify_notification_show'
collect2: error: ld returned 1 exit status

user@home:~/jabrac$ pkg-config --cflags --libs libnotify
-pthread -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libmount -I/usr/include/blkid -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -lnotify -lgdk_pixbuf-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0

CodePudding user response：

As @Someprogrammerdude said above, you need to specify the -l options after your program. Here is the relevant section from the gcc(1) man page:

-llibrary
...
It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, foo.o -lz bar.o searches library z after file foo.o but before bar.o. If bar.o refers to functions in z, those functions may not be loaded.