From: Stefan Monnier <monnier@iro.umontreal.ca>
Date: Thu, 8 Oct 2020 13:49:20 +0000 (-0400)
Subject: * src/ftcrfont.c (ftcrfont_open): Initialize the `max_width` field
X-Git-Tag: emacs-28.0.90~5712
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=c7804ac4018fb03787f291d7ef1739b34914d930;p=emacs.git

* src/ftcrfont.c (ftcrfont_open): Initialize the `max_width` field

On a 32bit build, Emacs can otherwise crash with a !FIXNUM_OVERFLOW_P
assertion in `Ffont_info` by simply doing `emacs -Q` and then `C-s`.

* src/font.c: Try and detect uninitialized `max_width` fields.
(font_make_object): Set max_width to a silly value.
(Ffont_info): Check the value is not silly any more.
---

diff --git a/src/font.c b/src/font.c
index 20686ce0ec0..fe257f47dc3 100644
--- a/src/font.c
+++ b/src/font.c
@@ -188,6 +188,9 @@ font_make_object (int size, Lisp_Object entity, int pixelsize)
 					     FONT_OBJECT_MAX, PVEC_FONT);
   int i;
 
+  /* Poison the max_width, so we can detect when it hasn't been set.  */
+  eassert (font->max_width = 1024 * 1024 * 1024);
+
   /* GC can happen before the driver is set up,
      so avoid dangling pointer here (Bug#17771).  */
   font->driver = NULL;
@@ -5171,6 +5174,9 @@ If the named font cannot be opened and loaded, return nil.  */)
     return Qnil;
   font = XFONT_OBJECT (font_object);
 
+  /* Sanity check to make sure we have initialized max_width.  */
+  eassert (XFONT_OBJECT (font_object)->max_width < 1024 * 1024 * 1024);
+
   info = CALLN (Fvector,
 		AREF (font_object, FONT_NAME_INDEX),
 		AREF (font_object, FONT_FULLNAME_INDEX),
diff --git a/src/ftcrfont.c b/src/ftcrfont.c
index 7832d4f5ce0..4892a34a3ab 100644
--- a/src/ftcrfont.c
+++ b/src/ftcrfont.c
@@ -187,7 +187,8 @@ ftcrfont_open (struct frame *f, Lisp_Object entity, int pixel_size)
 
   block_input ();
   cairo_glyph_t stack_glyph;
-  font->min_width = font->average_width = font->space_width = 0;
+  font->min_width = font->max_width = 0;
+  font->average_width = font->space_width = 0;
   for (char c = 32; c < 127; c++)
     {
       cairo_glyph_t *glyphs = &stack_glyph;
@@ -211,6 +212,8 @@ ftcrfont_open (struct frame *f, Lisp_Object entity, int pixel_size)
 	  && (! font->min_width
 	      || font->min_width > this_width))
 	font->min_width = this_width;
+      if (this_width > font->max_width)
+	font->max_width = this_width;
       if (c == 32)
 	font->space_width = this_width;
       font->average_width += this_width;
@@ -266,6 +269,7 @@ ftcrfont_open (struct frame *f, Lisp_Object entity, int pixel_size)
   font->relative_compose = 0;
   font->default_ascent = 0;
   font->vertical_centering = false;
+  eassert (font->max_width < 512 * 1024 * 1024);
 
   return font_object;
 }