Add assertions to guard against division by zero on sample text paths

There are a few code paths where pango_utf8_strwidth() is called on
language-specific sample text. The sample text should have been chosen
to never have a zero width, but we should add some assertions to ensure
that’s the case. This guides static analysers into the right analysis.

Coverity IDs: 1391697, 1391698, 1391699

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=778602

1 files changed, 7 insertions, 1 deletions

diff --git a/pango/pango-context.c b/pango/pango-context.c
index f91d0fe6..f0cea733 100644
--- a/pango/pango-context.c
+++ b/pango/pango-context.c
@@ -1635,6 +1635,10 @@ update_metrics_from_items (PangoFontMetrics *metrics,
   GHashTable *fonts_seen = g_hash_table_new (NULL, NULL);
   PangoGlyphString *glyphs = pango_glyph_string_new ();
   GList *l;
+  glong text_width;
+
+  /* This should typically be called with a sample text string. */
+  g_return_if_fail (text_len > 0);
 
   metrics->approximate_char_width = 0;
 
@@ -1663,7 +1667,9 @@ update_metrics_from_items (PangoFontMetrics *metrics,
   pango_glyph_string_free (glyphs);
   g_hash_table_destroy (fonts_seen);
 
-  metrics->approximate_char_width /= pango_utf8_strwidth (text);
+  text_width = pango_utf8_strwidth (text);
+  g_assert (text_width > 0);
+  metrics->approximate_char_width /= text_width;
 }
 
 /**