[Rosegarden-devel] scons build failure

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I tried using scons to configure and build RG from today's CVS 
and hit an error that stopped RG from compiling. It turned out that
liblo had not been detected at all during the scons configure.
Sorry if this is old news - I am still learning my way round scons...
Here is what happened:

I had a quite old liblo, so I downloaded a newer one version 0.16
and installed it in the default location /usr/local/lib:

 $ cd liblo-0.16; make install

For some reason scons seems to call pkg-config in such a way that
it fails to detect liblo in /usr/local/lib:

 $ cd rosegarden-cvs-20050619.pure
 $ scons configure
    scons: Reading SConscript files ...
    Checking for kde-config           :  kde-config was found
    Checking for kde version          :  3.4.0
    Checking for the qt library       :  qt is in /usr/lib/qt
    Checking for uic                  :  uic was found as /usr/lib/qt/bin/uic
    Checking for moc                  :  moc was found as /usr/lib/qt/bin/moc
    Checking for the qt includes      :  ok /usr/lib/qt/include/ 
    Checking for the kde includes     :  ok /opt/kde/include/
    Checking for int lirc_init() in C library lirc_client... no
    Checking for pkg-config ... yes
    Checking for alsa >= 1.0 ... yes
    Checking for jack >= 0.77 ... no
    Checking for dssi >= 0.4 ... no
    Checking for C header file ladspa.h... yes
    Checking for lrdf_init() in C library lrdf... no
    Checking for liblo >= 0.7 ... no
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    Checking for mad >= 0.10 ... no
    Checking for xft >= 2.1.0 ... yes
 $ echo $?
    0

scons has finished configuring RG with an exit status of 0.
It's not obvious that the failure to detect liblo is actually an error.
Unfortunately it causes the whole build to fail on sound/AlsaDriver.cpp:

   g++ -I/usr/include/alsa -I/usr/X11R6/include -I/usr/include/freetype2 -I/usr/include/freetype2/config -DHAVE_ALSA -DHAVE_LADSPA -DHAVE_XFT -DQT_THREAD_SUPPORT -DVERSION=\"4-1.1_cvs\" -I/opt/kde/include/ -I/usr/lib/qt/include/ -I/usr/include/alsa -I/usr/X11R6/include -I/usr/include/freetype2 -I/usr/include/freetype2/config -DHAVE_ALSA -DHAVE_LADSPA -DHAVE_XFT -O2 -DNDEBUG -DNO_DEBUG -Ibase -Igui -I. -Isound -c -o sound/AlsaDriver.o sound/AlsaDriver.cpp
   sound/AlsaDriver.cpp: In member function `virtual Rosegarden::MappedComposition* Rosegarden::AlsaDriver::getMappedComposition()':
   sound/AlsaDriver.cpp:2385: error: invalid use of undefined type `struct Rosegarden::ExternalTransport'
   sound/SoundDriver.h:135: error: forward declaration of `struct Rosegarden::ExternalTransport'
   sound/AlsaDriver.cpp:2385: error: incomplete type `Rosegarden::ExternalTransport' used in nested name specifier
   sound/AlsaDriver.cpp: In member function `void Rosegarden::AlsaDriver::handleMTCQFrame(unsigned int, Rosegarden::RealTime)':
   sound/AlsaDriver.cpp:2547: error: invalid use of undefined type `struct Rosegarden::ExternalTransport'
   sound/SoundDriver.h:135: error: forward declaration of `struct Rosegarden::ExternalTransport'
   sound/AlsaDriver.cpp:2548: error: incomplete type `Rosegarden::ExternalTransport' used in nested name specifier
   sound/AlsaDriver.cpp: In member function `bool Rosegarden::AlsaDriver::testForMTCSysex(const snd_seq_event_t*)':
   sound/AlsaDriver.cpp:2773: error: invalid use of undefined type `struct Rosegarden::ExternalTransport'
   sound/SoundDriver.h:135: error: forward declaration of `struct Rosegarden::ExternalTransport'
   sound/AlsaDriver.cpp:2774: error: incomplete type `Rosegarden::ExternalTransport' used in nested name specifier
   sound/AlsaDriver.cpp: In member function `bool Rosegarden::AlsaDriver::testForMMCSysex(const snd_seq_event_t*)':
   sound/AlsaDriver.cpp:2883: error: invalid use of undefined type `struct Rosegarden::ExternalTransport'
   sound/SoundDriver.h:135: error: forward declaration of `struct Rosegarden::ExternalTransport'
   sound/AlsaDriver.cpp:2883: error: incomplete type `Rosegarden::ExternalTransport' used in nested name specifier
   sound/AlsaDriver.cpp:2888: error: invalid use of undefined type `struct Rosegarden::ExternalTransport'
   sound/SoundDriver.h:135: error: forward declaration of `struct Rosegarden::ExternalTransport'
   sound/AlsaDriver.cpp:2888: error: incomplete type `Rosegarden::ExternalTransport' used in nested name specifier
   scons: *** [sound/AlsaDriver.o] Error 1
   scons: building terminated because of errors.

liblo version 0.16 was already installed in /usr/local/lib:

 $ cat /usr/local/lib/pkgconfig/liblo.pc
    prefix=/usr/local
    exec_prefix=${prefix}
    libdir=${exec_prefix}/lib
    includedir=${prefix}/include

    Name: liblo
    Version: 0.16
    Description: A lightweight OSC server/client library
    Libs: -L${libdir} -llo -lpthread
    Cflags: -I${includedir}

The problem according to strace and gdb is that scons blindly calls pkg-config
without adding /usr/local/lib to the environment variable PKG_CONFIG_PATH.
When this was done manually, scons detected liblo ok and the build completed ok:

 $ export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
 $ scons configure
    scons: Reading SConscript files ...
    Checking for kde-config           :  kde-config was found
    Checking for kde version          :  3.4.0
    Checking for the qt library       :  qt is in /usr/lib/qt
    Checking for uic                  :  uic was found as /usr/lib/qt/bin/uic
    Checking for moc                  :  moc was found as /usr/lib/qt/bin/moc
    Checking for the qt includes      :  ok /usr/lib/qt/include/ 
    Checking for the kde includes     :  ok /opt/kde/include/
    Checking for int lirc_init() in C library lirc_client... no
    Checking for pkg-config ... yes
    Checking for alsa >= 1.0 ... yes
    Checking for jack >= 0.77 ... no
    Checking for dssi >= 0.4 ... no
    Checking for C header file ladspa.h... yes
    Checking for lrdf_init() in C library lrdf... no
    Checking for liblo >= 0.7 ... yes
    Checking for mad >= 0.10 ... no
    Checking for xft >= 2.1.0 ... yes
 $ scons
    [...]
    scons: done building targets.

For comparison, the configure and build steps still work ok
using the traditional GNU autoconf method, i.e. there is no need
for manually setting up PKG_CONFIG_PATH.
Can we get scons and/or SConstruct files working like that?

William

Incidentally, why is scons reporting "two different environments" below?

 $ scons 
scons: Reading SConscript files ...

scons: warning: Two different environments were specified for target AlsaDriver.o,
        but they appear to have the same action: $CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
File "sound/SConscript", line 58, in ?

scons: warning: Two different environments were specified for target AlsaPort.o,
        but they appear to have the same action: $CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
File "sound/SConscript", line 58, in ?

scons: warning: Two different environments were specified for target JackDriver.o,
        but they appear to have the same action: $CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
File "sound/SConscript", line 58, in ?

scons: warning: Two different environments were specified for target PlayableAudioFile.o,
        but they appear to have the same action: $CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
File "sound/SConscript", line 58, in ?

scons: warning: Two different environments were specified for target SoundDriver.o,
        but they appear to have the same action: $CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
File "sound/SConscript", line 58, in ?

scons: warning: Two different environments were specified for target SoundDriverFactory.o,
        but they appear to have the same action: $CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
File "sound/SConscript", line 58, in ?
scons: done reading SConscript files.
scons: Building targets ...