Example libbu

Compiling against any of BRL-CAD's 20+ libraries is generally quite straight forward. Say you have a simple C++ source file named test.cpp using LIBBU, BRL-CAD's basic utility library:

#include "bu.h"
#include <iostream>

int
main(int ac, char *av[]) {
    bu_setprogname(av[0]);
    std::cout << "Program name is " << bu_getprogname() << std::endl;
    return 0;
}

To compile, you need to specify paths to headers (so the #include lines work).

  • For gcc/clang, this is usually -I options.

To link, you need to specify paths and libraries to link (so it can find functions).

  • For gcc/clang, this is usually -L options and -l options.

To run, you need to specify run paths to libraries (so it can use functions).

  • For gcc/clang, this is usually an -rpath linker option.

So say we put that test.cpp file in ~/brlcad and have BRL-CAD compiled at ~/brlcad/.build but not installed. (You don't need to install to use any library -- you just need to know where to find its headers and libraries!) After changing directory to ~/brlcad, we can compile and link our little test program:

c++ -c -Iinclude -I.build/include test.cpp
c++ test.o -L.build/lib -Wl,-rpath -Wl,.build/lib -lbu

Woot! Let's run to see it in action:

./a.out
Program name is a.out

So that's all there is to it! We can even simplify the entire process into one compile+link command if we are careful enough to make sure include flags come before source files and linker flags come after the source files, like this:

c++ -Iinclude -I.build/include test.cpp -L.build/lib -Wl,-rpath -Wl,.build/lib -lbu

From there, we can use any function in LIBBU. If we want to link against another library like LIBRT or LIBGED, we already have the right paths specified so we'd simply add -lrt or -lged respectively to the link line. To find functions, we can browse around the include/ headers and subdirectories as nearly every public function is documented in detail there, often with code snippet examples.

Even if we installed BRL-CAD into /opt/brlcad and want to use all headers and all the core libraries, the process remains the same. Specify paths to headers, source file(s), paths to libs, and then libs:

c++ -I/opt/brlcad/include -I/opt/brlcad/include/brlcad -I/opt/brlcad/include/openNURBS test.cpp -L/opt/brlcad/lib -Wl,-rpath -Wl,/opt/brlcad/lib -lged -lrt -lbn -lbu

Happy coding!