Library linking error

gavincangan · 06-22-2013, 10:34 AM

I'm trying to run a program that uses two libraries, PortAudio and kissFFT. I got an example program online written in C. But when I try to compile it using gcc compiler, I keep getting the error -ljack is missing.

I've installed JACK and I've added the path containing the file libjack.so.0 to $PATH and $LD_LIBRARY_PATH.

I also used the below command line tip I found online.
export LDFLAGS=" -rpath /usr/bin/libjack.so.0 " $LDFLAGS

But I still keep getting this error. Please help me out!!

NevemTeve · 06-22-2013, 10:46 AM

You should have a file called libjack.so
Normally it comes from package 'libjack-devel' (or similiar), but you might try this too:

Code:

cd /wherever/it/is
ln -s libjacket.so.0 libjacket.so

Note: /usr/bin is the wrong place for a shared lib, it should go to /usr/lib or /usr/local/lib

gavincangan · 06-22-2013, 10:51 AM

Could someone please explain to me the steps required to compile a program including library linking.
The usage of -l and -L switches especially.
I'm greatly confused by this!

gavincangan · 06-22-2013, 10:52 AM

I tried the command. But I still get the same error!
Btw what does that command do??

knudfl · 06-22-2013, 11:28 AM

Jack provides :
/usr/lib/libjackserver.so@ /usr/lib/libjack.so@
/usr/lib/libjackserver.so.0@ /usr/lib/libjack.so.0@
/usr/lib/libjackserver.so.0.1.0 /usr/lib/libjack.so.0.1.0

Or : The files could be in /usr/local/lib/,
if it is a manual install.

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NevemTeve · 06-22-2013, 11:29 AM

1. That's what 'man gcc' and 'man ld' is good for. Also read this: http://gcc.gnu.org/onlinedocs/gcc-4....l#Link-Options
2. Read 'man ln', and this: http://en.wikipedia.org/wiki/Symbolic_link

gavincangan · 06-22-2013, 04:30 PM

I read the man page about ln. I did understand that it was a link. But that still hasn't solved my problem.

Code:

[gavincangan@localhost ~]$ su --login
Password: 
[root@localhost ~]# cd /home/gavincangan/portaudio/portaudio/build/msvc/
[root@localhost msvc]# echo $LD_LIBRARY_PATH

[root@localhost msvc]# export LD_LIBRARY_PATH=/usr/bin
[root@localhost msvc]# echo $LD_LIBRARY_PATH
/usr/bin
[root@localhost msvc]# echo $PATH
/usr/lib64/ccache:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
[root@localhost msvc]# gcc -lrt -lasound -ljack -lpthread -o crosscorr paex_record.c libportaudio.a
/bin/ld: cannot find -ljack
collect2: error: ld returned 1 exit status
[root@localhost msvc]# export LDFLAGS="-rpath /usr/bin/libjack.so.0 " $LDFLAGS  
[root@localhost msvc]# gcc -lrt -lasound -ljack -lpthread -o crosscorr paex_record.c libportaudio.a
/bin/ld: cannot find -ljack
collect2: error: ld returned 1 exit status
[root@localhost msvc]# echo $LD_FLAGS

[root@localhost msvc]# export LDFLAGS="-rpath /usr/bin" $LDFLAGS  
-bash: export: `-rpath': not a valid identifier
-bash: export: `/usr/bin/libjack.so.0': not a valid identifier
[root@localhost msvc]# export LDFLAGS="-rpath /usr/bin " $LDFLAGS  
-bash: export: `-rpath': not a valid identifier
-bash: export: `/usr/bin': not a valid identifier
[root@localhost msvc]# export LDFLAGS="-rpath /usr/bin/libjack.so.0 " $LDFLAGS  
-bash: export: `-rpath': not a valid identifier
-bash: export: `/usr/bin': not a valid identifier
[root@localhost msvc]# cd /usr/bin/
[root@localhost bin]# ln -s libjack.so.0 libjack.so
[root@localhost bin]# cd /home/gavincangan/portaudio/portaudio/build/msvc/
[root@localhost msvc]# gcc -lrt -lasound -ljack -lpthread -o crosscorr paex_record.c libportaudio.a
/bin/ld: cannot find -ljack
collect2: error: ld returned 1 exit status
[root@localhost msvc]# man ln

Above is my terminal log. Please help me out with this.

I installed JACK using yum. In my comp I used find command and it found libjack.so and libjack.so.0 in /usr/bin

knudfl · 06-23-2013, 02:58 AM

Post # 7 .

Quote:

[root@localhost msvc]# export LD_LIBRARY_PATH=/usr/bin

! Please read post #2 : No libraries in /usr/bin/ !

Besides that : Don't use root for those user commands.
Root is for administrative tasks only. Export, make are user commands.

Also : May be you didn't install the jack development files ? ?
Which OS are you using ?
Debian style : # apt-get install libjack-jackd2-dev
Redhat style : # yum install jack-audio-connection-kit-devel

Quote:

[root@localhost bin]# ln -s libjack.so.0 libjack.so

Why ? There shouldn't be any libs in /usr/bin/.
Please test with $ ls -l /usr/bin/ | grep lib

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NevemTeve · 06-23-2013, 03:14 AM

To OP: Where these commands came from? They make no sense at all.

For a start, try to determine what OS/distribution do you have.

theNbomr · 06-26-2013, 10:18 AM

Linker options:

Code:

-lsomelibrary and -L /some/directory

The '-l' option names a library to link to the executable object module. The name of the library immediately follows the 'l' and does not include the conventional 'lib' filename prefix nor the '.so' suffix. So, for example, to link a motif library named 'libXm.so', you would use the linker option '-lXm'.
Having been told what libraries to link, the linker needs also to know where to look for libraries. The '-L' option takes one directory name as an argument, and the linker will add the specified directory to it's list of places to look for libraries. The directory name argument is not specific to any particular library, so does not associate with any particular '-l' option.
The resulting executable object module will still need to be able to find the shared object library at runtime, and that is the purpose of $LD_LIBRARY_PATH and/or /etc/ld.so.conf. It allows the linking loader to find the libraries against which the runtime binary was linked. Static linking obviates the need for these, at the expense of drastically inflated object module size.

--- rod.

ta0kira · 06-26-2013, 07:47 PM

Quote:

Originally Posted by gavincangan

I also used the below command line tip I found online.
export LDFLAGS=" -rpath /usr/bin/libjack.so.0 " $LDFLAGS

But I still keep getting this error. Please help me out!!

-rpath only helps at run-time. It hard-codes an additional library path (e.g. /usr/libexec/yourapp) into a library or executable. It's generally used if you use -L when linking but plan to move (or leave) the dependency somewhere that's not a standard location, such as when you're building both a library and an executable during make and plan to move them both during make install. You would use -rpath-link to simulate a different -rpath for the purposes of resolving dependencies of dependencies.

Kevin Barry