[dev] Xft(?) bug with emoji

[Alexander Krotov]

I have reduced dmenu segfault down to a simple program:
https://bugs.freedesktop.org/show_bug.cgi?id=107531

Please read the program and see if you can tell what is wrong or
confirm a bug. Apparently the bug is in fontconfig.

Running dwm with "pango" patch doesn't help either, so I think the
problem is in fontconfig and not Xft.

Also there are many bugfixes since 2.13.0 related to null ponter
dereferences, so maybe the bug is already fixed:
https://cgit.freedesktop.org/fontconfig/log/

/*
gcc bug.c -lX11 -lXft -I /usr/include/freetype2 -lfontconfig
*/
#include <stdio.h>

#include <X11/Xlib.h>
#include <X11/Xft/Xft.h>

int main(void) {
	Display *dpy = XOpenDisplay(NULL);
	if(dpy == NULL)
		return 1;
	int screen = DefaultScreen(dpy);

	char *fontname = "monospace:size=10";
	XftFont *xfont = XftFontOpenName(dpy, screen, fontname);
	if(xfont == NULL) {
		printf("Can't load font pattern");
		return 1;
	}
	FcPattern *pattern = FcNameParse((FcChar8 *) fontname);
	if (pattern == NULL) {
		printf("Can't parse name to pattern");
		return 1;
	}
	
	long utf8codepoint = 0x1F4D3; // notebook emoji

	FcCharSet *fccharset = FcCharSetCreate ();
	FcCharSetAddChar(fccharset, utf8codepoint);
	FcPatternAddCharSet(pattern, FC_CHARSET, fccharset);
	FcPatternAddBool(pattern, FC_SCALABLE, FcTrue);

	FcConfigSubstitute(NULL, pattern, FcMatchPattern);
	FcDefaultSubstitute(pattern);
	FcResult result;
	// drw.c uses XftFontMatch here
	FcFontMatch (NULL, pattern, &result);

	XCloseDisplay(dpy);
}