Make a gtk button label bold - c

Question

How can I make a Gtk button label bold?
I know how to set a label markup as:
GtkWidget *label = gtk_label_new(NULL);
gtk_label_set_markup(GTK_LABEL(label), "<b>Text to be bold</b>");
but not sure how to pass the argument to:
gtk_button_set_label()

Answer 1

The following pygtk code to make Bold Label Button should be easy to translate in C
# Create "Quit" button
button = gtk.Button("")
for child in button.get_children():
child.set_label("<b>Quit</b>")
child.set_use_markup(True)
# When the button is clicked, we call the main_quit function
# and the program exits
button.connect("clicked", lambda wid: gtk.main_quit())
# Insert the quit button
table.attach(button, 1,2,1,2, gtk.SHRINK|gtk.EXPAND|gtk.FILL)
button.show()

Answer 2

This code works for me
button = gtk_button_new_with_label("");
list = gtk_container_get_children(GTK_CONTAINER (button));
gtk_label_set_markup(GTK_LABEL(list->data), "<b>hello!</b>");

Answer 3

The issue is that gtk_button_new_with_label(...) does not accept NULL as valid param and thus things get wacky.
Below a minimal working example.
Compile using gcc $(pkg-config --libs --cflags gtk+-3.0) ./main.c && ./a.out
main.c:
#include <gtk/gtk.h>
#include "stdlib.h"
void mycb (GtkWidget *button, gpointer user_data)
{
GList *list;
GtkWidget *label;
list = gtk_container_get_children (GTK_CONTAINER (button));
// list should only contain one element, since the button can only hold one child
if (list->data && GTK_IS_LABEL (list->data)) {
// set the markup string
// for the markup syntax see
// https://developer.gnome.org/pygtk/stable/pango-markup-language.html
//gtk_label_set_markup (GTK_LABEL (list->data), "<span weight=\"bold\">hello markup A!</span>");
gtk_label_set_markup (GTK_LABEL (list->data), "hello <b>bold</b> markup");
} else {
label = gtk_label_new ("");
gtk_label_set_markup (GTK_LABEL (label), "hello <span style=\"italic\">italic </span> markup B!");
gtk_container_add (GTK_CONTAINER (button), label);
}
}
int main(int argc, char *argv[])
{
gtk_init (&argc, &argv);
GtkWidget *window;
GtkWidget *button;
GtkWidget *label;
GList *list;
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
button = gtk_button_new_with_label("no markup");
//button = gtk_button_new ();
#if 0
g_signal_connect (button, "clicked", G_CALLBACK (mycb), NULL);
#else
mycb(button, NULL);
#endif
gtk_container_add (GTK_CONTAINER (window), button);
gtk_widget_show_all (window);
gtk_main();
return EXIT_SUCCESS;
}