[gdk-pixbuf] tests: Add some assertions to check for zero-dimensioned images

[Philip Withnall <pwithnall src gnome org>]

commit 861a6dbea289d1ed98af1f66eb8024bc04464bd9
Author: Philip Withnall <withnall endlessm com>
Date:   Mon Feb 20 09:21:13 2017 +0000

    tests: Add some assertions to check for zero-dimensioned images
    
    This could happen if something in the test fails, so this allows early
    diagnosis of problems. It also hints to Coverity that the loops which
    follow can’t run (almost) infinitely due to the loop bounds being
    inverted.
    
    Coverity IDs: 1391987, 1399712
    
    https://bugzilla.gnome.org/show_bug.cgi?id=778943

 tests/pixbuf-scale-two-step.c |   31 +++++++++++++++++++++----------
 1 files changed, 21 insertions(+), 10 deletions(-)
---
diff --git a/tests/pixbuf-scale-two-step.c b/tests/pixbuf-scale-two-step.c
index 8050b30..d3f6886 100644
--- a/tests/pixbuf-scale-two-step.c
+++ b/tests/pixbuf-scale-two-step.c
@@ -62,26 +62,30 @@ pixdata_almost_equal (GdkPixbuf *one, GdkPixbuf *two)
   guchar *two_row;      /* Pointer to start of row of pixels in two */
   guchar *two_pixel;    /* Pointer to current pixel data in two */
   guint x, y;
+  gint width_one, height_one;
 
-  g_assert_cmpint (gdk_pixbuf_get_height (one), >=, 0);
-  g_assert_cmpint (gdk_pixbuf_get_width (one), >=, 0);
+  width_one = gdk_pixbuf_get_width (one);
+  height_one = gdk_pixbuf_get_height (one);
+
+  g_assert_cmpint (height_one, >=, 0);
+  g_assert_cmpint (width_one, >=, 0);
   g_assert_cmpint (gdk_pixbuf_get_height (two), >=, 0);
   g_assert_cmpint (gdk_pixbuf_get_width (two), >=, 0);
 
-  if (gdk_pixbuf_get_width (one) != gdk_pixbuf_get_width (two) ||
-      gdk_pixbuf_get_height (one) != gdk_pixbuf_get_height (two))
+  if (width_one != gdk_pixbuf_get_width (two) ||
+      height_one != gdk_pixbuf_get_height (two))
     {
       g_test_fail();
     }
 
   for (y = 0, one_row = gdk_pixbuf_get_pixels (one),
               two_row = gdk_pixbuf_get_pixels (two);
-       y < gdk_pixbuf_get_height (one);
+       y < height_one;
        y++, one_row += gdk_pixbuf_get_rowstride (one),
             two_row += gdk_pixbuf_get_rowstride (two))
     {
       for (x = 0, one_pixel = one_row, two_pixel = two_row;
-          x < gdk_pixbuf_get_width(one);
+          x < width_one;
           x++, one_pixel += gdk_pixbuf_get_n_channels (one),
                two_pixel += gdk_pixbuf_get_n_channels (two))
         {
@@ -188,21 +192,28 @@ crop_n_compare(const GdkPixbuf *source,   /* The source image */
     guchar *cropped_row;    /* Pointer to start of row of pixels in cropped */
     guchar *cropped_pixel;  /* Pointer to current pixel data in cropped */
     guint x, y;
+    gint scaled_width, scaled_height;
+
+    scaled_width = gdk_pixbuf_get_width (scaled);
+    scaled_height = gdk_pixbuf_get_height (scaled);
+
+    g_assert (scaled_width > 0);
+    g_assert (scaled_height > 0);
 
-    if (gdk_pixbuf_get_width (scaled) != gdk_pixbuf_get_width (cropped) ||
-       gdk_pixbuf_get_height (scaled) != gdk_pixbuf_get_height (cropped))
+    if (scaled_width != gdk_pixbuf_get_width (cropped) ||
+       scaled_height != gdk_pixbuf_get_height (cropped))
       {
         g_test_fail();
       }
 
     for (y = 0, scaled_row = gdk_pixbuf_get_pixels (scaled),
               cropped_row = gdk_pixbuf_get_pixels (cropped);
-        y < gdk_pixbuf_get_height (scaled);
+        y < scaled_height;
         y++, scaled_row += gdk_pixbuf_get_rowstride (scaled),
              cropped_row += gdk_pixbuf_get_rowstride (cropped))
       {
         for (x = 0, scaled_pixel = scaled_row, cropped_pixel = cropped_row;
-           x < gdk_pixbuf_get_width(scaled);
+           x < scaled_width;
            x++, scaled_pixel += gdk_pixbuf_get_n_channels (scaled),
                 cropped_pixel += gdk_pixbuf_get_n_channels (cropped))
          {