ext/gd: Fix GH-13082

Issue occur when compiling with recent clang releases (> 13) and
 with the '-Os' optimisation level, after using
`imageloadfont` which returns a proper GdFont class leads to
 a subtle bug when attempting to use via the imagefont* function.

NEWS

@@ -25,6 +25,10 @@ PHP                                                                        NEWS
     (Jakub Zelenka)
   . Fixed bug GH-12905 (FFI::new interacts badly with observers). (nielsdos)
 
+- GD:
+  . Fixed GH-13082 undefined behavior with GdFont instances handling with
+    imageload* and imagechar*. (David Carlier)
+
 - Intl:
   . Fixed GH-12943 (IntlDateFormatter::__construct accepts 'C' as valid locale).
     (David Carlier)

ext/gd/gd.c

@@ -2681,8 +2681,8 @@ static gdFontPtr php_find_gd_font(zend_object *font_obj, zend_long font_int)
  */
 static void php_imagefontsize(INTERNAL_FUNCTION_PARAMETERS, int arg)
 {
-	zend_object *font_obj;
+	zend_object *font_obj = NULL;
-	zend_long font_int;
+	zend_long font_int = 0;
 	gdFontPtr font;
 
 	ZEND_PARSE_PARAMETERS_START(1, 1)
@@ -2750,8 +2750,8 @@ static void php_imagechar(INTERNAL_FUNCTION_PARAMETERS, int mode)
 	int ch = 0, col, x, y, i, l = 0;
 	unsigned char *str = NULL;
 	zend_object *font_obj;
-	zend_long font_int;
+	zend_long font_int = 0;
-	gdFontPtr font;
+	gdFontPtr font = NULL;
 
 	ZEND_PARSE_PARAMETERS_START(6, 6)
 		Z_PARAM_OBJECT_OF_CLASS(IM, gd_image_ce)

ext/gd/tests/gh13082.phpt

@@ -0,0 +1,16 @@
+--TEST--
+GH-13082 - imagefontwidth/height unexpectedly throwing an exception on a valid GdFont object.
+--EXTENSIONS--
+gd
+--FILE--
+<?php
+    $font = imageloadfont(__DIR__ . "/gh13082.gdf");
+    if ($font === false) die("imageloadfont failed");
+    if (!($font instanceof GdFont)) die("invalid gd font");
+
+    var_dump(imagefontwidth($font));
+    var_dump(imagefontheight($font));
+?>
+--EXPECT--
+int(12)
+int(20)