master c7804ac: * src/ftcrfont.c (ftcrfont_open): Initialize the `max_width` field

[Stefan Monnier]

branch: master
commit c7804ac4018fb03787f291d7ef1739b34914d930
Author: Stefan Monnier <monnier@iro.umontreal.ca>
Commit: Stefan Monnier <monnier@iro.umontreal.ca>

    * 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.
---
 src/font.c     | 6 ++++++
 src/ftcrfont.c | 6 +++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/font.c b/src/font.c
index 20686ce..fe257f4 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 7832d4f..4892a34 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;
 }