Cppcheck report - cafe-control-center (cppcheck 2.13.0-2+b1): capplets/appearance/appearance-font.c

/*
 * Copyright (C) 2007 The GNOME Foundation
 * Written by Jonathan Blandford <jrb@gnome.org>
 *            Jens Granseuer <jensgr@gmx.net>
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "appearance.h"

#include <string.h>
#include <stdarg.h>
#include <math.h>

#include <glib/gi18n.h>
#include <gio/gio.h>
#include <cdk/cdkx.h>
#include <glib/gstdio.h>

#include "capplet-util.h"

/* X servers sometimes lie about the screen's physical dimensions, so we cannot
 * compute an accurate DPI value.  When this happens, the user gets fonts that
 * are too huge or too tiny.  So, we see what the server returns:  if it reports
 * something outside of the range [DPI_LOW_REASONABLE_VALUE,
 * DPI_HIGH_REASONABLE_VALUE], then we assume that it is lying and we use
 * DPI_FALLBACK instead.
 *
 * See get_dpi_from_cafe_conf_or_server() below, and also
 * https://bugzilla.novell.com/show_bug.cgi?id=217790
 */
#define DPI_FALLBACK 96
#define DPI_LOW_REASONABLE_VALUE 50
#define DPI_HIGH_REASONABLE_VALUE 500

static gboolean in_change = FALSE;

static void sample_draw(CtkWidget* darea, cairo_t* cr)
{
	cairo_surface_t* surface = g_object_get_data(G_OBJECT(darea), "sample-surface");
	CtkAllocation allocation;
	int x, y, w, h;

	ctk_widget_get_allocation (darea, &allocation);
	x = allocation.width;
	y = allocation.height;
	w = cairo_image_surface_get_width (surface);
	h = cairo_image_surface_get_height (surface);

	cairo_set_line_width (cr, 1);
	cairo_set_line_cap (cr, CAIRO_LINE_CAP_SQUARE);

	cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
	cairo_rectangle (cr, 0, 0, x, y);
	cairo_fill_preserve (cr);
	cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
	cairo_stroke (cr);

	cairo_set_source_surface (cr, surface, (x - w) / 2, (y - h) / 2);

	cairo_paint(cr);
}

typedef enum {
	ANTIALIAS_NONE,
	ANTIALIAS_GRAYSCALE,
	ANTIALIAS_RGBA
} Antialiasing;

typedef enum {
	HINT_NONE,
	HINT_SLIGHT,
	HINT_MEDIUM,
	HINT_FULL
} Hinting;

typedef enum {
	RGBA_RGB,
	RGBA_BGR,
	RGBA_VRGB,
	RGBA_VBGR
} RgbaOrder;

static void set_fontoptions(PangoContext *context, Antialiasing antialiasing, Hinting hinting)
{
	cairo_font_options_t *opt;
	cairo_antialias_t aa;
	cairo_hint_style_t hs;

	switch (antialiasing) {
	case ANTIALIAS_NONE:
		aa = CAIRO_ANTIALIAS_NONE;
		break;
	case ANTIALIAS_GRAYSCALE:
		aa = CAIRO_ANTIALIAS_GRAY;
		break;
	case ANTIALIAS_RGBA:
		aa = CAIRO_ANTIALIAS_SUBPIXEL;
		break;
	default:
		aa = CAIRO_ANTIALIAS_DEFAULT;
		break;
	}

	switch (hinting) {
	case HINT_NONE:
		hs = CAIRO_HINT_STYLE_NONE;
		break;
	case HINT_SLIGHT:
		hs = CAIRO_HINT_STYLE_SLIGHT;
		break;
	case HINT_MEDIUM:
		hs = CAIRO_HINT_STYLE_MEDIUM;
		break;
	case HINT_FULL:
		hs = CAIRO_HINT_STYLE_FULL;
		break;
	default:
		hs = CAIRO_HINT_STYLE_DEFAULT;
		break;
	}

	opt = cairo_font_options_create ();
	cairo_font_options_set_antialias (opt, aa);
	cairo_font_options_set_hint_style (opt, hs);
	pango_cairo_context_set_font_options (context, opt);
	cairo_font_options_destroy (opt);
}

static void setup_font_sample(CtkWidget* darea, Antialiasing antialiasing, Hinting hinting)
{
	const char *str = "<span font=\"18\" style=\"normal\">abcfgop AO </span>"
					  "<span font=\"20\" style=\"italic\">abcfgop</span>";

	PangoContext *context;
	PangoLayout *layout;
	PangoFontDescription *fd;
	PangoRectangle extents;
	cairo_surface_t *surface;
	cairo_t *cr;
	int width, height;

	context = ctk_widget_get_pango_context (darea);
	set_fontoptions (context, antialiasing, hinting);
	layout = pango_layout_new (context);

	fd = pango_font_description_from_string ("Serif");
	pango_layout_set_font_description (layout, fd);
	pango_font_description_free (fd);

	pango_layout_set_markup (layout, str, -1);

	pango_layout_get_extents (layout, NULL, &extents);
	width = PANGO_PIXELS(extents.width) + 4;
	height = PANGO_PIXELS(extents.height) + 2;

	surface = cairo_image_surface_create (CAIRO_FORMAT_A8, width, height);
	cr = cairo_create (surface);

	cairo_move_to (cr, 2, 1);
	pango_cairo_show_layout (cr, layout);
	g_object_unref (layout);
	cairo_destroy (cr);

	g_object_set_data_full(G_OBJECT(darea), "sample-surface", surface, (GDestroyNotify) cairo_surface_destroy);

	ctk_widget_set_size_request (CTK_WIDGET(darea), width + 2, height + 2);
	g_signal_connect(darea, "draw", G_CALLBACK(sample_draw), NULL);
}

/*
 * Code implementing a group of radio buttons with different cairo option combinations.
 * If one of the buttons is matched by the GSettings key, we pick it. Otherwise we
 * show the group as inconsistent.
 */

typedef struct {
  Antialiasing antialiasing;
  Hinting hinting;
  CtkToggleButton *radio;
} FontPair;

static GSList *font_pairs = NULL;

static void
font_render_load (GSettings *settings)
{
  Antialiasing antialiasing;
  Hinting hinting;
  gboolean inconsistent = TRUE;
  GSList *tmp_list;

  antialiasing = g_settings_get_enum (settings, FONT_ANTIALIASING_KEY);
  hinting = g_settings_get_enum (settings, FONT_HINTING_KEY);

  in_change = TRUE;

  for (tmp_list = font_pairs; tmp_list; tmp_list = tmp_list->next) {
    FontPair *pair = tmp_list->data;

    if (antialiasing == pair->antialiasing && hinting == pair->hinting) {
      ctk_toggle_button_set_active (pair->radio, TRUE);
      inconsistent = FALSE;
      break;
    }
  }

  for (tmp_list = font_pairs; tmp_list; tmp_list = tmp_list->next) {
    FontPair *pair = tmp_list->data;

    ctk_toggle_button_set_inconsistent (pair->radio, inconsistent);
  }

  in_change = FALSE;
}

static void
font_render_changed (GSettings *settings,
                     gchar     *key,
                     gpointer   user_data)
{
  font_render_load (settings);
}

static void
font_radio_toggled (CtkToggleButton *toggle_button,
		    FontPair        *pair)
{
  if (!in_change) {
    GSettings *settings = g_settings_new (FONT_RENDER_SCHEMA);

    g_settings_set_enum (settings, FONT_ANTIALIASING_KEY, pair->antialiasing);
    g_settings_set_enum (settings, FONT_HINTING_KEY, pair->hinting);

    /* Restore back to the previous state until we get notification */
    font_render_load (settings);
    g_object_unref (settings);
  }
}

static void
setup_font_pair (CtkWidget    *radio,
		 CtkWidget    *darea,
		 Antialiasing  antialiasing,
		 Hinting       hinting)
{
  FontPair *pair = g_new (FontPair, 1);

  pair->antialiasing = antialiasing;
  pair->hinting = hinting;
  pair->radio = CTK_TOGGLE_BUTTON (radio);

  setup_font_sample (darea, antialiasing, hinting);
  font_pairs = g_slist_prepend (font_pairs, pair);

  g_signal_connect (radio, "toggled",
		    G_CALLBACK (font_radio_toggled), pair);
}

static void
croma_titlebar_load_sensitivity (AppearanceData *data)
{
  ctk_widget_set_sensitive (appearance_capplet_get_widget (data, "window_title_font"),
			    !g_settings_get_boolean (data->croma_settings,
						    WINDOW_TITLE_USES_SYSTEM_KEY));
}

static void
croma_changed (GSettings *settings,
	       gchar     *entry,
	       gpointer   user_data)
{
  croma_titlebar_load_sensitivity (user_data);
}

/*
 * EnumGroup - a group of radio buttons for a gsettings enum
 */
typedef struct
{
  GSettings *settings;
  GSList *items;
  gchar *settings_key;
  gulong settings_signal_id;
} EnumGroup;

typedef struct
{
  EnumGroup *group;
  CtkToggleButton *widget;
  int value;
} EnumItem;

static void
enum_group_load (EnumGroup *group)
{
  gint val = g_settings_get_enum (group->settings, group->settings_key);
  GSList *tmp_list;

  in_change = TRUE;

  for (tmp_list = group->items; tmp_list; tmp_list = tmp_list->next) {
    EnumItem *item = tmp_list->data;

    if (val == item->value)
      ctk_toggle_button_set_active (item->widget, TRUE);
  }

  in_change = FALSE;
}

static void
enum_group_changed (GSettings *settings,
		    gchar     *key,
		    gpointer  user_data)
{
  enum_group_load (user_data);
}

static void
enum_item_toggled (CtkToggleButton *toggle_button,
		   EnumItem        *item)
{
  EnumGroup *group = item->group;

  if (!in_change) {
    g_settings_set_enum (group->settings, group->settings_key, item->value);
  }

  /* Restore back to the previous state until we get notification */
  enum_group_load (group);
}

static EnumGroup *
enum_group_create (GSettings           *settings,
		   const gchar         *settings_key,
		   CtkWidget           *first_widget,
		   ...)
{
  EnumGroup *group;
  CtkWidget *widget;
  va_list args;

  group = g_new (EnumGroup, 1);

  group->settings = g_object_ref (settings);
  group->settings_key = g_strdup (settings_key);
  group->items = NULL;

  va_start (args, first_widget);

  widget = first_widget;
  while (widget) {
    EnumItem *item;

    item = g_new (EnumItem, 1);
    item->group = group;
    item->widget = CTK_TOGGLE_BUTTON (widget);
    item->value = va_arg (args, int);

    g_signal_connect (item->widget, "toggled",
		      G_CALLBACK (enum_item_toggled), item);

    group->items = g_slist_prepend (group->items, item);

    widget = va_arg (args, CtkWidget *);
  }

  va_end (args);

  enum_group_load (group);

  gchar *signal_name = g_strdup_printf("changed::%s", settings_key);
  group->settings_signal_id = g_signal_connect (settings, signal_name,
                                                G_CALLBACK (enum_group_changed), group);
  g_free (signal_name);

  return group;
}

static void
enum_group_destroy (EnumGroup *group)
{
  g_signal_handler_disconnect (group->settings, group->settings_signal_id);
  g_clear_object (&group->settings);
  group->settings_signal_id = 0;
  g_free (group->settings_key);

  g_slist_foreach (group->items, (GFunc) g_free, NULL);
  g_slist_free (group->items);

  g_free (group);
}

static double
dpi_from_pixels_and_mm (int pixels, int mm)
{
  double dpi;

  if (mm >= 1)
    dpi = pixels / (mm / 25.4);
  else
    dpi = 0;

  return dpi;
}

static double
get_dpi_from_x_server (void)
{
  CdkScreen  *screen;
  double dpi;

  screen = cdk_screen_get_default ();

  if (screen) {
    double width_dpi, height_dpi;

    Screen *xscreen = cdk_x11_screen_get_xscreen (screen);

    width_dpi = dpi_from_pixels_and_mm (WidthOfScreen (xscreen), WidthMMOfScreen (xscreen));
    height_dpi = dpi_from_pixels_and_mm (HeightOfScreen (xscreen), HeightMMOfScreen (xscreen));

    if (width_dpi < DPI_LOW_REASONABLE_VALUE || width_dpi > DPI_HIGH_REASONABLE_VALUE ||
        height_dpi < DPI_LOW_REASONABLE_VALUE || height_dpi > DPI_HIGH_REASONABLE_VALUE)
      dpi = DPI_FALLBACK;
    else
      dpi = (width_dpi + height_dpi) / 2.0;
  } else {
    /* Huh!?  No screen? */
    dpi = DPI_FALLBACK;
  }

  return dpi;
}

/*
 * The font rendering details dialog
 */
static void
dpi_load (GSettings     *settings,
	  CtkSpinButton *spinner)
{
  CdkScreen *screen;
  gint scale;
  gdouble dpi;

  screen = cdk_screen_get_default ();
  scale = cdk_window_get_scale_factor (cdk_screen_get_root_window (screen));
  dpi = g_settings_get_double (settings, FONT_DPI_KEY);

  if (dpi == 0)
    dpi = get_dpi_from_x_server ();

  dpi *= (double)scale;
  dpi = CLAMP(dpi, DPI_LOW_REASONABLE_VALUE, DPI_HIGH_REASONABLE_VALUE);

  in_change = TRUE;
  ctk_spin_button_set_value (spinner, dpi);
  in_change = FALSE;
}

static void
dpi_changed (GSettings      *settings,
	     gchar          *key,
	     AppearanceData *data)
{
  CtkWidget *spinner;
  CtkWidget *toggle;
  gdouble dpi;

  dpi = g_settings_get_double (data->font_settings, FONT_DPI_KEY);
  spinner = appearance_capplet_get_widget (data, "dpi_spinner");
  toggle = appearance_capplet_get_widget (data, "dpi_reset_switch");

  dpi_load (settings, CTK_SPIN_BUTTON (spinner));

  ctk_switch_set_state (CTK_SWITCH (toggle), dpi == 0);
  ctk_widget_set_sensitive (spinner, dpi != 0);
}

static void
monitors_changed (CdkScreen      *screen,
		  AppearanceData *data)
{
  CtkWidget *widget;
  widget = appearance_capplet_get_widget (data, "dpi_spinner");
  dpi_load (data->font_settings, CTK_SPIN_BUTTON (widget));
}

static void
dpi_value_changed (CtkSpinButton  *spinner,
		   AppearanceData *data)
{
  /* Like any time when using a spin button with GSettings, there is
   * a race condition here. When we change, we send the new
   * value to GSettings, then restore to the old value until
   * we get a response to emulate the proper model/view behavior.
   *
   * If the user changes the value faster than responses are
   * received from GSettings, this may cause mildly strange effects.
   */
  if (!in_change) {
    CdkScreen *screen;
    CtkWidget *toggle;
    gint scale;
    gdouble new_dpi;

    screen = cdk_screen_get_default ();
    scale = cdk_window_get_scale_factor (cdk_screen_get_root_window (screen));
    new_dpi = ctk_spin_button_get_value (spinner) / (double)scale;

    g_settings_set_double (data->font_settings, FONT_DPI_KEY, new_dpi);

    dpi_load (data->font_settings, spinner);

    toggle = appearance_capplet_get_widget (data, "dpi_reset_switch");
    ctk_switch_set_active (CTK_SWITCH (toggle), FALSE);
  }
}

static gboolean
dpi_value_reset (CtkSwitch      *toggle,
		 gboolean        state,
		 AppearanceData *data)
{
  CtkWidget *spinner;
  spinner = appearance_capplet_get_widget (data, "dpi_spinner");

  if (state)
    g_settings_set_double (data->font_settings, FONT_DPI_KEY, 0);
  else
    dpi_value_changed (CTK_SPIN_BUTTON (spinner), data);

  ctk_switch_set_state(toggle, state);
  ctk_widget_set_sensitive (spinner, !state);

  return TRUE;
}

static void
cb_details_response (CtkDialog *dialog, gint response_id)
{
  if (response_id == CTK_RESPONSE_HELP) {
    capplet_help (CTK_WINDOW (dialog),
		  "goscustdesk-38");
  } else
    ctk_widget_hide (CTK_WIDGET (dialog));
}

static void install_new_font (const gchar *filepath)
{
    GFile *src, *dst;
    gchar *fontdir, *fontpath;
    char *basename;
    GError *error = NULL;

    fontdir = g_build_filename (g_get_home_dir(), ".fonts", NULL);
    if (!g_file_test (fontdir, G_FILE_TEST_IS_DIR))
    {
        if(g_mkdir (fontdir, 0755) != 0) {
            g_free (fontdir);
            return;
        }
    }
    g_free (fontdir);

    basename = g_path_get_basename (filepath);
    fontpath = g_build_filename (g_get_home_dir(), ".fonts", basename, NULL);
    g_free (basename);
    src = g_file_new_for_path (filepath);
    dst = g_file_new_for_path (fontpath);
    g_free (fontpath);

    if (!g_file_copy (src,
                      dst,
                      G_FILE_COPY_NONE,
                      NULL,
                      NULL,
                      NULL,
                      &error)) {
        g_warning ("install new font failed: %s\n", error->message);
        g_error_free (error);
    }
    g_object_unref (src);
    g_object_unref (dst);
}

static void
cb_add_new_font (CtkWidget *button,
                 AppearanceData *data)
{
    CtkWidget *dialog;
    CtkFileFilter *filter;
    CtkFileChooser *chooser;
    CtkFileChooserAction action = CTK_FILE_CHOOSER_ACTION_OPEN;
    gint res;

    dialog = ctk_file_chooser_dialog_new (_("Select Font"),
            CTK_WINDOW (appearance_capplet_get_widget (data, "appearance_window")),
            action,
            _("_Cancel"),
            CTK_RESPONSE_CANCEL,
            _("_Open"),
            CTK_RESPONSE_ACCEPT,
            NULL);
    chooser = CTK_FILE_CHOOSER (dialog);
    filter = ctk_file_filter_new ();
    ctk_file_filter_set_name (filter, _("Fonts"));
    ctk_file_filter_add_mime_type (filter, "font/ttf");
    ctk_file_chooser_add_filter (chooser, filter);

    res = ctk_dialog_run (CTK_DIALOG (dialog));
    if (res == CTK_RESPONSE_ACCEPT)
    {
        char *filename;
        filename = ctk_file_chooser_get_filename (chooser);
        install_new_font (filename);
        g_free (filename);
    }
    ctk_widget_destroy (dialog);
}

static void
cb_show_details (CtkWidget *button,
		 AppearanceData *data)
{
  if (!data->font_details) {
    CtkAdjustment *adjustment;
    CtkWidget *spinner;
    CtkWidget *toggle;
    EnumGroup *group;
    gdouble dpi;

    data->font_details = appearance_capplet_get_widget (data, "render_details");

    ctk_window_set_transient_for (CTK_WINDOW (data->font_details),
                                  CTK_WINDOW (appearance_capplet_get_widget (data, "appearance_window")));

    spinner = appearance_capplet_get_widget (data, "dpi_spinner");
    toggle = appearance_capplet_get_widget (data, "dpi_reset_switch");

    /* Set initial state for widgets */
    dpi = g_settings_get_double (data->font_settings, FONT_DPI_KEY);
    ctk_switch_set_active (CTK_SWITCH (toggle), dpi == 0);
    ctk_widget_set_sensitive (CTK_WIDGET (spinner), dpi != 0);

    /* pick a sensible maximum dpi */
    adjustment = ctk_spin_button_get_adjustment (CTK_SPIN_BUTTON (spinner));
    ctk_adjustment_set_lower (adjustment, DPI_LOW_REASONABLE_VALUE);
    ctk_adjustment_set_upper (adjustment, DPI_HIGH_REASONABLE_VALUE);
    ctk_adjustment_set_step_increment (adjustment, 1);

    dpi_load (data->font_settings, CTK_SPIN_BUTTON (spinner));
    g_signal_connect (spinner, "value-changed",
		      G_CALLBACK (dpi_value_changed), data);
    g_signal_connect (toggle, "state-set",
		      G_CALLBACK (dpi_value_reset), data);

    g_signal_connect (data->font_settings, "changed::" FONT_DPI_KEY, G_CALLBACK (dpi_changed), data);

    /* Update font DPI when window scaling factor is changed */
    g_signal_connect (cdk_screen_get_default (), "monitors-changed", G_CALLBACK (monitors_changed), data);

    setup_font_sample (appearance_capplet_get_widget (data, "antialias_none_sample"),      ANTIALIAS_NONE,      HINT_SLIGHT);
    setup_font_sample (appearance_capplet_get_widget (data, "antialias_grayscale_sample"), ANTIALIAS_GRAYSCALE, HINT_SLIGHT);
    setup_font_sample (appearance_capplet_get_widget (data, "antialias_subpixel_sample"),  ANTIALIAS_RGBA,      HINT_SLIGHT);

    group = enum_group_create (
    	data->font_settings, FONT_ANTIALIASING_KEY,
	appearance_capplet_get_widget (data, "antialias_none_radio"),      ANTIALIAS_NONE,
	appearance_capplet_get_widget (data, "antialias_grayscale_radio"), ANTIALIAS_GRAYSCALE,
	appearance_capplet_get_widget (data, "antialias_subpixel_radio"),  ANTIALIAS_RGBA,
<--- Passing NULL after the last typed argument to a variadic function leads to undefined behaviour. [+]
Passing NULL after the last typed argument to a variadic function leads to undefined behaviour.
The C99 standard, in section 7.15.1.1, states that if the type used by va_arg() is not compatible with the type of the actual next argument (as promoted according to the default argument promotions), the behavior is undefined.
The value of the NULL macro is an implementation-defined null pointer constant (7.17), which can be any integer constant expression with the value 0, or such an expression casted to (void*) (6.3.2.3). This includes values like 0, 0L, or even 0LL.
In practice on common architectures, this will cause real crashes if sizeof(int) != sizeof(void*), and NULL is defined to 0 or any other null pointer constant that promotes to int.
To reproduce you might be able to use this little code example on 64bit platforms. If the output includes "ERROR", the sentinel had only 4 out of 8 bytes initialized to zero and was not detected as the final argument to stop argument processing via va_arg(). Changing the 0 to (void*)0 or 0L will make the "ERROR" output go away.
#include <stdarg.h>
#include <stdio.h>

void f(char *s, ...) {
    va_list ap;
    va_start(ap,s);
    for (;;) {
        char *p = va_arg(ap,char*);
        printf("%018p, %s\n", p, (long)p & 255 ? p : "");
        if(!p) break;
    }
    va_end(ap);
}

void g() {
    char *s2 = "x";
    char *s3 = "ERROR";

    // changing 0 to 0L for the 7th argument (which is intended to act as sentinel) makes the error go away on x86_64
    f("first", s2, s2, s2, s2, s2, 0, s3, (char*)0);
}

void h() {
    int i;
    volatile unsigned char a[1000];
    for (i = 0; i<sizeof(a); i++)
        a[i] = -1;
}

int main() {
    h();
    g();
    return 0;
}
	NULL);
    data->font_groups = g_slist_prepend (data->font_groups, group);

    setup_font_sample (appearance_capplet_get_widget (data, "hint_none_sample"),   ANTIALIAS_RGBA, HINT_NONE);
    setup_font_sample (appearance_capplet_get_widget (data, "hint_slight_sample"), ANTIALIAS_RGBA, HINT_SLIGHT);
    setup_font_sample (appearance_capplet_get_widget (data, "hint_medium_sample"), ANTIALIAS_RGBA, HINT_MEDIUM);
    setup_font_sample (appearance_capplet_get_widget (data, "hint_full_sample"),   ANTIALIAS_RGBA, HINT_FULL);

    group = enum_group_create (data->font_settings, FONT_HINTING_KEY,
                               appearance_capplet_get_widget (data, "hint_none_radio"),   HINT_NONE,
                               appearance_capplet_get_widget (data, "hint_slight_radio"), HINT_SLIGHT,
                               appearance_capplet_get_widget (data, "hint_medium_radio"), HINT_MEDIUM,
                               appearance_capplet_get_widget (data, "hint_full_radio"),   HINT_FULL,
<--- Passing NULL after the last typed argument to a variadic function leads to undefined behaviour. [+]
Passing NULL after the last typed argument to a variadic function leads to undefined behaviour.
The C99 standard, in section 7.15.1.1, states that if the type used by va_arg() is not compatible with the type of the actual next argument (as promoted according to the default argument promotions), the behavior is undefined.
The value of the NULL macro is an implementation-defined null pointer constant (7.17), which can be any integer constant expression with the value 0, or such an expression casted to (void*) (6.3.2.3). This includes values like 0, 0L, or even 0LL.
In practice on common architectures, this will cause real crashes if sizeof(int) != sizeof(void*), and NULL is defined to 0 or any other null pointer constant that promotes to int.
To reproduce you might be able to use this little code example on 64bit platforms. If the output includes "ERROR", the sentinel had only 4 out of 8 bytes initialized to zero and was not detected as the final argument to stop argument processing via va_arg(). Changing the 0 to (void*)0 or 0L will make the "ERROR" output go away.
#include <stdarg.h>
#include <stdio.h>

void f(char *s, ...) {
    va_list ap;
    va_start(ap,s);
    for (;;) {
        char *p = va_arg(ap,char*);
        printf("%018p, %s\n", p, (long)p & 255 ? p : "");
        if(!p) break;
    }
    va_end(ap);
}

void g() {
    char *s2 = "x";
    char *s3 = "ERROR";

    // changing 0 to 0L for the 7th argument (which is intended to act as sentinel) makes the error go away on x86_64
    f("first", s2, s2, s2, s2, s2, 0, s3, (char*)0);
}

void h() {
    int i;
    volatile unsigned char a[1000];
    for (i = 0; i<sizeof(a); i++)
        a[i] = -1;
}

int main() {
    h();
    g();
    return 0;
}
                               NULL);
    data->font_groups = g_slist_prepend (data->font_groups, group);

    ctk_image_set_from_file (CTK_IMAGE (appearance_capplet_get_widget (data, "subpixel_rgb_image")),
                             CAFECC_PIXMAP_DIR "/subpixel-rgb.png");
    ctk_image_set_from_file (CTK_IMAGE (appearance_capplet_get_widget (data, "subpixel_bgr_image")),
                             CAFECC_PIXMAP_DIR "/subpixel-bgr.png");
    ctk_image_set_from_file (CTK_IMAGE (appearance_capplet_get_widget (data, "subpixel_vrgb_image")),
                             CAFECC_PIXMAP_DIR "/subpixel-vrgb.png");
    ctk_image_set_from_file (CTK_IMAGE (appearance_capplet_get_widget (data, "subpixel_vbgr_image")),
                             CAFECC_PIXMAP_DIR "/subpixel-vbgr.png");

    group = enum_group_create (data->font_settings, FONT_RGBA_ORDER_KEY,
                               appearance_capplet_get_widget (data, "subpixel_rgb_radio"),  RGBA_RGB,
                               appearance_capplet_get_widget (data, "subpixel_bgr_radio"),  RGBA_BGR,
                               appearance_capplet_get_widget (data, "subpixel_vrgb_radio"), RGBA_VRGB,
                               appearance_capplet_get_widget (data, "subpixel_vbgr_radio"), RGBA_VBGR,
<--- Passing NULL after the last typed argument to a variadic function leads to undefined behaviour. [+]
Passing NULL after the last typed argument to a variadic function leads to undefined behaviour.
The C99 standard, in section 7.15.1.1, states that if the type used by va_arg() is not compatible with the type of the actual next argument (as promoted according to the default argument promotions), the behavior is undefined.
The value of the NULL macro is an implementation-defined null pointer constant (7.17), which can be any integer constant expression with the value 0, or such an expression casted to (void*) (6.3.2.3). This includes values like 0, 0L, or even 0LL.
In practice on common architectures, this will cause real crashes if sizeof(int) != sizeof(void*), and NULL is defined to 0 or any other null pointer constant that promotes to int.
To reproduce you might be able to use this little code example on 64bit platforms. If the output includes "ERROR", the sentinel had only 4 out of 8 bytes initialized to zero and was not detected as the final argument to stop argument processing via va_arg(). Changing the 0 to (void*)0 or 0L will make the "ERROR" output go away.
#include <stdarg.h>
#include <stdio.h>

void f(char *s, ...) {
    va_list ap;
    va_start(ap,s);
    for (;;) {
        char *p = va_arg(ap,char*);
        printf("%018p, %s\n", p, (long)p & 255 ? p : "");
        if(!p) break;
    }
    va_end(ap);
}

void g() {
    char *s2 = "x";
    char *s3 = "ERROR";

    // changing 0 to 0L for the 7th argument (which is intended to act as sentinel) makes the error go away on x86_64
    f("first", s2, s2, s2, s2, s2, 0, s3, (char*)0);
}

void h() {
    int i;
    volatile unsigned char a[1000];
    for (i = 0; i<sizeof(a); i++)
        a[i] = -1;
}

int main() {
    h();
    g();
    return 0;
}
                               NULL);
    data->font_groups = g_slist_prepend (data->font_groups, group);

    g_signal_connect (G_OBJECT (data->font_details),
		      "response",
		      G_CALLBACK (cb_details_response), NULL);
    g_signal_connect (G_OBJECT (data->font_details),
		      "delete_event",
		      G_CALLBACK (ctk_true), NULL);
  }

  ctk_window_present (CTK_WINDOW (data->font_details));
}

void font_init(AppearanceData* data)
{
	CtkWidget* widget;

	data->font_details = NULL;
	data->font_groups = NULL;

	widget = appearance_capplet_get_widget(data, "application_font");
	g_settings_bind (data->interface_settings,
			 CTK_FONT_KEY,
			 G_OBJECT (widget),
			 "font-name",
			 G_SETTINGS_BIND_DEFAULT);

	widget = appearance_capplet_get_widget (data, "document_font");
	g_settings_bind (data->interface_settings,
			 DOCUMENT_FONT_KEY,
			 G_OBJECT (widget),
			 "font-name",
			 G_SETTINGS_BIND_DEFAULT);

	widget = appearance_capplet_get_widget (data, "desktop_font");

	if (data->baul_settings)
		g_settings_bind (data->baul_settings,
				 DESKTOP_FONT_KEY,
				 G_OBJECT (widget),
				 "font-name",
				 G_SETTINGS_BIND_DEFAULT);
	else
		ctk_widget_set_sensitive (widget, FALSE);

	widget = appearance_capplet_get_widget (data, "window_title_font");
	g_settings_bind (data->croma_settings,
			 WINDOW_TITLE_FONT_KEY,
			 G_OBJECT (widget),
			 "font-name",
			 G_SETTINGS_BIND_DEFAULT);

	widget = appearance_capplet_get_widget (data, "monospace_font");
	g_settings_bind (data->interface_settings,
			 MONOSPACE_FONT_KEY,
			 G_OBJECT (widget),
			 "font-name",
			 G_SETTINGS_BIND_DEFAULT);

	g_signal_connect (data->croma_settings,
			  "changed::" WINDOW_TITLE_USES_SYSTEM_KEY,
			  G_CALLBACK (croma_changed),
			  data);

	g_signal_connect (appearance_capplet_get_widget (data, "add_new_font"), "clicked", G_CALLBACK (cb_add_new_font), data);

	croma_titlebar_load_sensitivity(data);

	setup_font_pair(appearance_capplet_get_widget(data, "monochrome_radio"), appearance_capplet_get_widget (data, "monochrome_sample"), ANTIALIAS_NONE, HINT_FULL);
	setup_font_pair(appearance_capplet_get_widget(data, "best_shapes_radio"), appearance_capplet_get_widget (data, "best_shapes_sample"), ANTIALIAS_GRAYSCALE, HINT_MEDIUM);
	setup_font_pair(appearance_capplet_get_widget(data, "best_contrast_radio"), appearance_capplet_get_widget (data, "best_contrast_sample"), ANTIALIAS_GRAYSCALE, HINT_FULL);
	setup_font_pair(appearance_capplet_get_widget(data, "subpixel_radio"), appearance_capplet_get_widget (data, "subpixel_sample"), ANTIALIAS_RGBA, HINT_SLIGHT);

	font_render_load (data->font_settings);

	g_signal_connect (data->font_settings, "changed", G_CALLBACK (font_render_changed), NULL);

	g_signal_connect (appearance_capplet_get_widget (data, "details_button"), "clicked", G_CALLBACK (cb_show_details), data);
}

void font_shutdown(AppearanceData* data)
{
	g_slist_foreach(data->font_groups, (GFunc) enum_group_destroy, NULL);
	g_slist_free(data->font_groups);
	g_slist_foreach(font_pairs, (GFunc) g_free, NULL);
	g_slist_free(font_pairs);
}