Linking the library, built from source

[rdmills]

Hi there,

I'm trying to link the static library libmatplot.a to compile the simple line_plot example, with a view to use matplot++ for my own project.

Source

#include <cmath>
#include <matplot/matplot.h>

int main() {
    using namespace matplot;
    std::vector<double> x = linspace(0, 2 * pi);
    std::vector<double> y = transform(x, [](auto x) { return sin(x); });

    plot(x, y, "-o");
    hold(on);
    plot(x, transform(y, [](auto y) { return -y; }), "--xr");
    plot(x, transform(x, [](auto x) { return x / pi - 1.; }), "-:gs");
    plot({1.0, 0.7, 0.4, 0.0, -0.4, -0.7, -1}, "k");

    show();
    return 0;
}

I'm linking with

g++ -o plot_1 plot_1.o /usr/local/lib/libmatplot.a

Output

/usr/bin/ld: /usr/local/lib/libmatplot.a(common.cpp.o): in function `cimg_library::CImg<unsigned char>::_save_png(_IO_FILE*, char const*, unsigned int) const [clone .isra.0]':
common.cpp:(.text+0x83cc): undefined reference to `png_create_write_struct'
/usr/bin/ld: common.cpp:(.text+0x83e1): undefined reference to `png_create_info_struct'
/usr/bin/ld: common.cpp:(.text+0x8403): undefined reference to `png_set_longjmp_fn'
/usr/bin/ld: common.cpp:(.text+0x8423): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: common.cpp:(.text+0x8499): undefined reference to `png_init_io'
/usr/bin/ld: common.cpp:(.text+0x84fe): undefined reference to `png_set_IHDR'
/usr/bin/ld: common.cpp:(.text+0x850f): undefined reference to `png_write_info'
/usr/bin/ld: common.cpp:(.text+0x8d46): undefined reference to `png_write_image'
/usr/bin/ld: common.cpp:(.text+0x8d53): undefined reference to `png_write_end'
/usr/bin/ld: common.cpp:(.text+0x8d60): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: common.cpp:(.text+0x9c01): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: /usr/local/lib/libmatplot.a(common.cpp.o): in function `cimg_library::CImg<unsigned char
...

I get verbose asking for references to what I thought were optional dependencies.

Matplot++ was built from source, with no issues as far as I can tell.

Best regards,

Rory

[alandefreitas]

Linking libraries manually nowadays is a very bad idea. The dependencies are optional when compiling the library. Once the library is compiled with them, they're no longer optional. To link everything manually, you would have to get every dependency and compiler definition right in the command line. This is almost impossible.

[rdmills]

Thanks. How would you recommend best integrating Matplot++ as an external lib?

[alandefreitas]

CMake. Always CMake. :)