Question

I have an application I’m building that’s using the NetCDF C++ library, and NetCDF is pulling in the HDF-4 libary. However, it’s pulling in the wrong HDF-4 library.

Here’s how my app is linked:

/apps1/intel/bin/icpc -gxx-name=/apps1/gcc-4.5.0/bin/g++ -shared -o lib/libMyCustom.so
  -Llib  -L/apps1/boost-1.48.0/lib -Wl,-rpath=/apps1/boost-1.48.0/lib
  -L/apps1/gdal-1.8.0-jasper/lib -Wl,-rpath=/apps1/gdal-1.8.0-jasper/lib
  -L/new_apps1/hdf4/lib -Wl,-rpath=/new_apps1/hdf4/lib -L/new_apps1/netcdf/lib
  -Wl,-rpath=/new_apps1/netcdf/lib -lboost_system -lboost_serialization
  -lboost_date_time -lboost_thread -lgdal -ldf -lmfhdf -lnetcdf_c++ 
  MyProj/obj/ProjUtility.o  MyProj/obj/ProjMetadataException.o
  MyProj/obj/ProjTimestampUtil.o 

I have set my LD_LIBRARY_PATH very short:

LD_LIBRARY_PATH=/new_apps1/hdf4/lib:/new_apps1/hdf5/lib:
  /apps1/intel/composerxe/lib/intel64:/apps1/gcc-4.5.0/lib64:/apps1/gcc-4.5.0/lib

And here is an excerpt from the ldd -v output:

    libdf.so.0 => /new_apps1/hdf4/lib/libdf.so.0 (0x00002af5baabc000)
    libmfhdf.so.0 => /new_apps1/hdf4/lib/libmfhdf.so.0 (0x00002af5bad61000)
    libnetcdf_c++.so.5 => /new_apps1/netcdf/lib/libnetcdf_c++.so.5 (0x00002af5baf85000)
    libhdf5.so.6 => /new_apps1/hdf5/lib/libhdf5.so.6 (0x00002af5bd1e7000)
    libgif.so.4 => /usr/lib64/libgif.so.4 (0x0000003a6bc00000)
    libpng12.so.0 => /usr/lib64/libpng12.so.0 (0x0000003a71000000)
    libnetcdf.so.6 => /new_apps1/netcdf/lib/libnetcdf.so.6 (0x00002af5bd682000)
    libhdf5_hl.so.6 => /new_apps1/hdf5/lib/libhdf5_hl.so.6 (0x00002af5be272000)

    /new_apps1/hdf4/lib/libdf.so.0:
            libc.so.6 (GLIBC_2.3) => /lib64/libc.so.6
            libc.so.6 (GLIBC_2.2.5) => /lib64/libc.so.6
    /new_apps1/hdf4/lib/libmfhdf.so.0:
            libc.so.6 (GLIBC_2.2.5) => /lib64/libc.so.6
    /new_apps1/netcdf/lib/libnetcdf_c++.so.5:
            libgcc_s.so.1 (GCC_3.0) => /apps1/gcc-4.5.0/lib64/libgcc_s.so.1
            libc.so.6 (GLIBC_2.2.5) => /lib64/libc.so.6
            libstdc++.so.6 (CXXABI_1.3) => /apps1/gcc-4.5.0/lib64/libstdc++.so.6
            libstdc++.so.6 (GLIBCXX_3.4) => /apps1/gcc-4.5.0/lib64/libstdc++.so.6
    /new_apps1/hdf5/lib/libhdf5.so.6:
            libm.so.6 (GLIBC_2.2.5) => /lib64/libm.so.6
            libc.so.6 (GLIBC_2.3) => /lib64/libc.so.6
            libc.so.6 (GLIBC_2.2.5) => /lib64/libc.so.6
    /new_apps1/netcdf/lib/libnetcdf.so.6:
            libm.so.6 (GLIBC_2.2.5) => /lib64/libm.so.6
            libc.so.6 (GLIBC_2.3) => /lib64/libc.so.6
            libc.so.6 (GLIBC_2.2.5) => /lib64/libc.so.6
    /new_apps1/hdf5/lib/libhdf5_hl.so.6:
            libc.so.6 (GLIBC_2.2.5) => /lib64/libc.so.6

So far, everything in the LD_LIBRARY_PATH, rpath, and ldd indicate that it’s pointing to the HDF that I want to reference (/new_apps1/hdf4/lib/libmfhdf.so.0). But when I run, Valgrind is telling me that it’s dying in the OLD HDF-4 library (which is probably why it’s segfaulting), instead of the HDF-4 library I’m attempting to link against:

 Invalid read of size 4
    at 0x67CF765: NC_var_shape (in /apps1/hdf-4.2.6/lib/libmfhdf.so.0.0.0)
    by 0x91327CA: nc_get_NC (v1hpg.c:1113)
    by 0x91303C0: l3nc__open_mp (nc.c:1096)
    by 0x915B279: nc3d__open_mp (dapdispatch3.c:336)
    by 0x914A752: nc3d_open (ncdap3.c:94)
    by 0x911F8A2: l4nc_open_file (nc4file.c:2338)
    by 0x916A290: nc4d_open_file (ncdap4.c:122)
    by 0x911CDDF: nc__open (nc4file.c:2407)
    by 0x69E85F8: NcFile::NcFile(char const*, NcFile::FileMode, unsigned long*, unsigned long, NcFile::FileFormat) (netcdf.cpp:384)
    by 0x710F0B8: getData(std::string const&) (ProjTimestampUtil.cc:593)
    by 0x70E9BEA: (anonymous namespace)::parseOptions(int, char**) (ProjUtility.cc:190)
    by 0x70EAAFB: main(int, char**) (ProjUtility.cc:243)
  Address 0x1051 is not stack'd, malloc'd or (recently) free'd


 Process terminating with default action of signal 11 (SIGSEGV)
  Access not within mapped region at address 0x1051
    at 0x67CF765: NC_var_shape (in /apps1/hdf-4.2.6/lib/libmfhdf.so.0.0.0)
    by 0x91327CA: nc_get_NC (v1hpg.c:1113)
    by 0x91303C0: l3nc__open_mp (nc.c:1096)
    by 0x915B279: nc3d__open_mp (dapdispatch3.c:336)
    by 0x914A752: nc3d_open (ncdap3.c:94)
    by 0x911F8A2: l4nc_open_file (nc4file.c:2338)
    by 0x916A290: nc4d_open_file (ncdap4.c:122)
    by 0x911CDDF: nc__open (nc4file.c:2407)
    by 0x69E85F8: NcFile::NcFile(char const*, NcFile::FileMode, unsigned long*, unsigned long, NcFile::FileFormat) (netcdf.cpp:384)
    by 0x710F0B8: getData(std::string const&) (ProjTimestampUtil.cc:593)
    by 0x70E9BEA: (anonymous namespace)::parseOptions(int, char**) (ProjUtility.cc:190)
    by 0x70EAAFB: main(int, char**) (ProjUtility.cc:243)

Where else is my app getting path info when dynamically pulling in other libraries?

Answer 1

I’m not exactly sure of all the details of how -rpath and LD_LIBRARY_PATH work, and their precedence, but I did find some useful environment variables:

• LD_DEBUG=all – This env variable turns on verbose dynamic linker debugging. Now doing an ldd on your app will spew output about the details of how all its dependencies find their dependencies.
• LD_DEBUG_OUTPUT=<filename_prefix> – Used in conjunction with LD_DEBUG to specify output files to log the debugging info to.

The LD_DEBUG env variable helped me track down that /apps1/gdal-1.8.0-jasper/lib/libgdal.so.1 was compiled with an -rpath option that was pulling the old (wrong) versions of my libraries. It gave this helpful debug output:

search path=/pathXYZ/lib/tls/x86_64:/pathXYZ/lib/tls:/pathXYZ/lib/x86_64:
  /pathABC/jasper/lib:/pathABC/hdf5/lib/tls/x86_64:/pathABC/hdf5/lib/tls:
  /pathABC/hdf5/lib/x86_64:/pathABC/hdf5/lib:/pathABC/netcdf/lib/tls/x86_64:
  /pathABC/netcdf/lib/tls:/pathABC/netcdf/lib/x86_64:/pathABC/netcdf/lib

          (RPATH from file /apps1/gdal-1.8.0-jasper/lib/libgdal.so.1)

So the rpath of how the GDAL library was compiled seemed to be making an end-run around my LD_LIBRAR_PATH. Until I can get my lab team to rebuild libgdal correctly, I found this env var, which helped me load the “right” library versions that I wanted:

• LD_PRELOAD=<path/to/libName.so> – Point this to the location of a library (or a space-separated list of libraries) that should be loaded before all others. See the ld.so man page.