How to include and use cairo graphics library in C?

Question

I have recently downloaded and installed Cairo graphics library for C from the project website.

I tried to run the hello world program of Cairo by using the given code from the site FAQ. In Terminal, I applied the same command as given by the same page to compile it. But when I tried to compile it, errors of undefined references appeared.

In the Terminal, the output is:

 cc -o hello $(pkg-config --cflags --libs cairo) hello.c
 /tmp/cco08jEN.o: In function `main':
 hello.c:(.text+0x1f): undefined reference to `cairo_image_surface_create'
 hello.c:(.text+0x2f): undefined reference to `cairo_create'
 hello.c:(.text+0x4e): undefined reference to `cairo_select_font_face'
 hello.c:(.text+0x6d): undefined reference to `cairo_set_font_size'
 hello.c:(.text+0x89): undefined reference to `cairo_set_source_rgb'
 hello.c:(.text+0xbb): undefined reference to `cairo_move_to'
 hello.c:(.text+0xcc): undefined reference to `cairo_show_text'
 hello.c:(.text+0xd8): undefined reference to `cairo_destroy'
 hello.c:(.text+0xe9): undefined reference to `cairo_surface_write_to_png'
 hello.c:(.text+0xf5): undefined reference to `cairo_surface_destroy'
 collect2: error: ld returned 1 exit status

And my source code is:

#include <cairo.h>

int
main (int argc, char *argv[])
{
    cairo_surface_t *surface =
        cairo_image_surface_create (CAIRO_FORMAT_ARGB32, 240, 80);
    cairo_t *cr =
        cairo_create (surface);

    cairo_select_font_face (cr, "serif", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_BOLD);
    cairo_set_font_size (cr, 32.0);
    cairo_set_source_rgb (cr, 0.0, 0.0, 1.0);
    cairo_move_to (cr, 10.0, 50.0);
    cairo_show_text (cr, "Hello, world");

    cairo_destroy (cr);
    cairo_surface_write_to_png (surface, "hello.png");
    cairo_surface_destroy (surface);
    return 0;
}

as described from the site FAQ.

I am a beginner in using Terminal commands, and Cairo is the first third party library I used for graphics. I tried to find any fix from the Internet, but I didn't get any clue nor fix.

Please tell me my error, and explain to me how to use the libraries.

Calista

Please post those screen shots as formatted text in the question. – Isreal

You have a linking problem. As @WeatherVane says, post the details of how you built and tried to run it. – Donata

The screen shot falls down because there must have been a previous error before cairo_create, from cairo_image_surface_create. It does not get as far as linking: the compiler cannot find the header file <cairo.h>. You have to set up the paths to headers and library somewhere. – Isreal

Answer 1

Do this instead:

cc hello.c -o hello $(pkg-config --cflags --libs cairo)

Let's take a quote from the book, An Introduction to GCC - for the GNU compilers gcc and g++.

The traditional behavior of linkers is to search for external functions from left to right in the libraries specified on the command line. This means that a library containing the definition of a function should appear after any source files or object files which use it. This includes libraries specified with the shortcut -l option.

Given that information, doing:

cc -o hello $(pkg-config --cflags --libs cairo) hello.c

would mean that hello.c would not be able to get the function definitions of the Cairo graphics library.

On the other hand, if you do this:

cc hello.c -o hello $(pkg-config --cflags --libs cairo)

would mean that hello.c would be able to get the functions definitions of the Cairo graphics library. Take note that the command above is equivalent to cc -o hello hello.c $(pkg-config --cflags --libs cairo).

More information here, and here.

Bohon

Very Very thank you sir this worked, again thanks for your help. – Calista