Linking with third-party libraries

[blooglet]

I'm trying to use two external libraries called jrtplib and jthread within a Qt project, but I'm not sure how I do this. I've compiled it from source and I've obtained shared objects named libjrtp.so.3.9.1 and libjrtp.so.3.9.1. I added the header files as well.

These are the files I copied from the source:

> ls -R headers
headers:
jrtplib  jthread
 
headers/jrtplib:
rtcpapppacket.h              rtpbyteaddress.h          rtpkeyhashtable.h    rtpsessionparams.h
rtcpbyepacket.h              rtpcollisionlist.h        rtplibraryversion.h  rtpsessionsources.h
rtcpcompoundpacketbuilder.h  rtpconfig.h               rtpmemorymanager.h   rtpsourcedata.h
rtcpcompoundpacket.h         rtpdebug.h                rtpmemoryobject.h    rtpsources.h
rtcppacketbuilder.h          rtpdefines.h              rtppacketbuilder.h   rtpstructs.h
rtcppacket.h                 rtperrors.h               rtppacket.h          rtptimeutilities.h
rtcprrpacket.h               rtpexternaltransmitter.h  rtppollthread.h      rtptransmitter.h
rtcpscheduler.h              rtphashtable.h            rtprandom.h          rtptypes.h
rtcpsdesinfo.h               rtpinternalsourcedata.h   rtprandomrand48.h    rtptypes_win.h
rtcpsdespacket.h             rtpipv4address.h          rtprandomrands.h     rtpudpv4transmitter.h
rtcpsrpacket.h               rtpipv4destination.h      rtprandomurandom.h   rtpudpv6transmitter.h
rtcpunknownpacket.h          rtpipv6address.h          rtprawpacket.h
rtpaddress.h                 rtpipv6destination.h      rtpsession.h
 
headers/jthread:
jmutexautolock.h  jmutex.h  jthreadconfig.h  jthread.h
> ls -R libs
libs:
libjrtp.so  libjrtp.so.3.9.1  libjthread.so  libjthread.so.1.3.1

> ls -R headers
headers:
jrtplib  jthread

headers/jrtplib:
rtcpapppacket.h              rtpbyteaddress.h          rtpkeyhashtable.h    rtpsessionparams.h
rtcpbyepacket.h              rtpcollisionlist.h        rtplibraryversion.h  rtpsessionsources.h
rtcpcompoundpacketbuilder.h  rtpconfig.h               rtpmemorymanager.h   rtpsourcedata.h
rtcpcompoundpacket.h         rtpdebug.h                rtpmemoryobject.h    rtpsources.h
rtcppacketbuilder.h          rtpdefines.h              rtppacketbuilder.h   rtpstructs.h
rtcppacket.h                 rtperrors.h               rtppacket.h          rtptimeutilities.h
rtcprrpacket.h               rtpexternaltransmitter.h  rtppollthread.h      rtptransmitter.h
rtcpscheduler.h              rtphashtable.h            rtprandom.h          rtptypes.h
rtcpsdesinfo.h               rtpinternalsourcedata.h   rtprandomrand48.h    rtptypes_win.h
rtcpsdespacket.h             rtpipv4address.h          rtprandomrands.h     rtpudpv4transmitter.h
rtcpsrpacket.h               rtpipv4destination.h      rtprandomurandom.h   rtpudpv6transmitter.h
rtcpunknownpacket.h          rtpipv6address.h          rtprawpacket.h
rtpaddress.h                 rtpipv6destination.h      rtpsession.h

headers/jthread:
jmutexautolock.h  jmutex.h  jthreadconfig.h  jthread.h
> ls -R libs
libs:
libjrtp.so  libjrtp.so.3.9.1  libjthread.so  libjthread.so.1.3.1

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I added the following flag to the qmake file:

INCLUDEPATH += ../headers
LIBS += ../libs/libjrtp.so ../libs/libjthread.so

INCLUDEPATH += ../headers
LIBS += ../libs/libjrtp.so ../libs/libjthread.so

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To test the library, I added #include <jthread/jmutex.h> and put this in the main function:

jthread::JMutex mutex;
    mutex.Lock();
    mutex.Unlock();

jthread::JMutex mutex;
    mutex.Lock();
    mutex.Unlock();

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I see this when I try to run this program:

Debugging starts
&"warning: GDB: Failed to set controlling terminal: Invalid argument\n"
error while loading shared libraries: libjrtp.so.3.9.1: cannot open shared object file: No such file or directory
Debugging has finished

Debugging starts
&"warning: GDB: Failed to set controlling terminal: Invalid argument\n"
error while loading shared libraries: libjrtp.so.3.9.1: cannot open shared object file: No such file or directory
Debugging has finished

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This looks like a dynamic linking failure. Other than that I've seen no warning signs. What am I doing wrong? Perhaps there is a way to statically link with jrtplib to avoid issues. I realize that I didn't use LIBS like everyone else (LIBS += -l../libs/libjrtp.so -l../libs/libjthread.so), but that only gave me more errors. Leaving out the LIBS statement quite logically causes qmake to fail to link to the library (undefined reference to `jthread::JMutex::JMutex()' etc).

[fullmetalcoder]

Under Linux, the recommended approach is to install your 3rd party libraries in standard system locations (headers in /usr/include and shared libs in /usr/lib for instance). This has two benefits :

• you can use the more portable

  LIBS += -ljrtp

  LIBS += -ljrtp

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  idiom in the project file and dispense from specifying an extra include path
• you don't have to worry about LD_LIBRARY_PATH (this is the reason the shared lib is not found in your case)

If you want to bundle the 3rd party libs with your app, the best approach is probably static linking (provided it is supported by the libs of interest).

[blooglet]

That worked for me. Thanks for your advice!