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Prateek
Asked: 2014-04-25 05:02:51 +0800 CST

How do I deal with "undefined reference to dlopen" errors while compiling and using OpenFST on Ubuntu?

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Trying to compile and use OpenFST on Ubuntu 13.10 leads to link errors like "undefined references to dlopen". How does one fix this? Searching online suggests including -ldl in the gcc command line, but that is not sufficient.

dynamic-linking

2 Answers

  1. Best Answer

    Compile as follows:

    ./configure LDFLAGS=-Wl,--no-as-needed
make
sudo make install

    To compile your a.cpp which uses the library, do

    g++ -I /usr/local/include a.cpp /usr/local/lib/libfst.so -Wl,--no-as-needed -ldl

    It is important the -ldl appears after -Wl,--no-as-needed.

    Running your program works as you'd expect from the README provided by OpenFST, you just need to have /usr/local/lib in your LD_LIBRARY_PATH. For example,

    LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/lib" ./a.out
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  2. As can be seen in the Catalogue of Built-In Rules:

    Linking a single object file

    n is made automatically from n.o by running the linker (usually called ld) via the C compiler. The precise recipe used is:

    $(CC) $(LDFLAGS) n.o $(LOADLIBES) $(LDLIBS)

    and Variables Used by Implicit Rules:

    LDFLAGS

    Extra flags to give to compilers when they are supposed to invoke the linker, ld, such as -L. Libraries (-lfoo) should be added to the LDLIBS variable instead.

    So in this case -ldl should be set or added to LDLIBS, not LDFLAGS.

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