[test] Add new test text-zero-len (#5177)

The test passes an empty string to cairo_show_text, cairo_text_path, and
cairo_text_extents, and NULL and an invalid pointer, with zero num_glyphs to
cairo_show_glyphs, cairo_glyph_path, and cairo_glyph_extents.

test/.gitignore

@@ -126,6 +126,7 @@ text-antialias-subpixel
 text-cache-crash
 text-pattern
 text-rotate
+text-zero-len
 transforms
 translate-show-surface
 trap-clip

test/Makefile.am

@@ -90,6 +90,7 @@ text-antialias-subpixel		\
 text-cache-crash		\
 text-pattern			\
 text-rotate			\
+text-zero-len			\
 transforms			\
 translate-show-surface		\
 trap-clip			\
@@ -320,6 +321,7 @@ text-pattern-svg-argb32-ref.png				\
 text-pattern-svg-rgb24-ref.png				\
 text-rotate-ref.png					\
 text-rotate-rgb24-ref.png				\
+text-zero-len-ref.png					\
 transforms-ref.png					\
 translate-show-surface-ref.png				\
 trap-clip-ref.png					\

test/text-zero-len.c

@@ -0,0 +1,88 @@
+/*
+ * Copyright © 2006 Red Hat, Inc.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software
+ * and its documentation for any purpose is hereby granted without
+ * fee, provided that the above copyright notice appear in all copies
+ * and that both that copyright notice and this permission notice
+ * appear in supporting documentation, and that the name of
+ * Red Hat, Inc. not be used in advertising or publicity pertaining to
+ * distribution of the software without specific, written prior
+ * permission. Red Hat, Inc. makes no representations about the
+ * suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * RED HAT, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
+ * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS, IN NO EVENT SHALL RED HAT, INC. BE LIABLE FOR ANY SPECIAL,
+ * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
+ * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+ * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Author: Behdad Esfahbod <behdad@behdad.org>
+ */
+
+/* Related bug 5177
+ *
+ * In short:
+ *
+ * _cairo_atsui_font_text_to_glyph with a zero-sized string crashes.
+ *
+ * Moreover, the fallback path in cairo_scaled_font_text_to_glyphs()
+ * when handling a zero-sized string, allocates a zero-sized glyph array
+ * and when NULL is returned by malloc, recognizes that as an out-of-memory
+ * error.  The glibc implementation of malloc() does not return NULL from
+ * malloc(0), but I don't think it's a safe assumption.
+ *
+ * By just bailing out on zero-sized text, we fix both issues.
+ */
+
+#include "cairo-test.h"
+
+#define WIDTH  60
+#define HEIGHT 60
+#define NUM_TEXT 20
+#define TEXT_SIZE 12
+
+static cairo_test_draw_function_t draw;
+
+cairo_test_t test = {
+    "text-zero-len",
+    "Tests show_text and text_path with a zero-sized string",
+    WIDTH, HEIGHT,
+    draw
+};
+
+/* Draw the word cairo at NUM_TEXT different angles */
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_text_extents_t extents;
+
+    cairo_select_font_face (cr, "Bitstream Vera Sans",
+			    CAIRO_FONT_SLANT_NORMAL,
+			    CAIRO_FONT_WEIGHT_NORMAL);
+    cairo_set_font_size (cr, 16);
+
+    cairo_move_to (cr, 10, 25);
+    cairo_show_text (cr, "");
+    cairo_show_glyphs (cr, NULL, 0);
+    cairo_show_glyphs (cr, (void*)8, 0);
+
+    cairo_move_to (cr, 10, 55);
+    cairo_text_path (cr, "");
+    cairo_glyph_path (cr, (void*)8, 0);
+    cairo_fill (cr);
+
+    cairo_text_extents (cr, "", &extents);
+    cairo_glyph_extents (cr, (void*)8, 0, &extents);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+int
+main (void)
+{
+    return cairo_test (&test);
+}