Problem report #17

[Dan Nicolaescu]

This one appeared on May 15th, and it seems to be related to the
crashes reported on the pretest list. 

Can somebody please take a look?

CID: 17
Checker: FORWARD_NULL (help)
File: base/src/emacs/src/xfaces.c
Function: best_matching_font
Description: Variable "best" tracked as NULL was dereferenced.


6591    static char *
6592    best_matching_font (f, attrs, fonts, nfonts, width_ratio, 
needs_overstrike)
6593         struct frame *f;
6594         Lisp_Object *attrs;
6595         struct font_name *fonts;
6596         int nfonts;
6597         int width_ratio;
6598         int *needs_overstrike;
6599    {
6600      char *font_name;
6601      struct font_name *best;
6602      int i, pt = 0;
6603      int specified[5];
6604      int exact_p, avgwidth;
6605    
6606      if (nfonts == 0)
6607        return NULL;
6608    
6609      /* Make specified font attributes available in `specified',
6610         indexed by sort order.  */
6611      for (i = 0; i < DIM (font_sort_order); ++i)
6612        {
6613          int xlfd_idx = font_sort_order[i];
6614    
6615          if (xlfd_idx == XLFD_SWIDTH)
6616            specified[i] = face_numeric_swidth (attrs[LFACE_SWIDTH_INDEX]);
6617          else if (xlfd_idx == XLFD_POINT_SIZE)
6618            specified[i] = pt = XFASTINT (attrs[LFACE_HEIGHT_INDEX]);
6619          else if (xlfd_idx == XLFD_WEIGHT)
6620            specified[i] = face_numeric_weight (attrs[LFACE_WEIGHT_INDEX]);
6621          else if (xlfd_idx == XLFD_SLANT)
6622            specified[i] = face_numeric_slant (attrs[LFACE_SLANT_INDEX]);
6623          else
6624            abort ();
6625        }
6626    
6627      avgwidth = (UNSPECIFIEDP (attrs[LFACE_AVGWIDTH_INDEX])
6628                  ? 0
6629                  : XFASTINT (attrs[LFACE_AVGWIDTH_INDEX]) * width_ratio);
6630    
6631      exact_p = 0;
6632    
6633      if (needs_overstrike)
6634        *needs_overstrike = 0;
6635    
6636      best = NULL;
6637    
6638      /* Find the best match among the non-scalable fonts.  */
6639      for (i = 1; i < nfonts; ++i)
6640        if (!font_scalable_p (fonts + i)
6641            && better_font_p (specified, fonts + i, best, 1, avgwidth))
6642          {
6643            best = fonts + i;
6644    
6645            exact_p = exact_face_match_p (specified, best, avgwidth);
6646            if (exact_p)
6647              break;
6648          }
6649    
6650      /* Unless we found an exact match among non-scalable fonts, see if
6651         we can find a better match among scalable fonts.  */
6652      if (!exact_p)
6653        {
6654          /* A scalable font is better if
6655    
6656             1. its weight, slant, swidth attributes are better, or.
6657    
6658             2. the best non-scalable font doesn't have the required
6659             point size, and the scalable fonts weight, slant, swidth
6660             isn't worse.  */
6661    
6662          int non_scalable_has_exact_height_p;
6663    

Event var_compare_op: Added "best" due to comparison "best != 0"
Also see events: [var_deref_op]
At conditional (1): "best != 0" taking false path

6664          if (best && best->numeric[XLFD_POINT_SIZE] == pt)
6665            non_scalable_has_exact_height_p = 1;
6666          else
6667            non_scalable_has_exact_height_p = 0;
6668    

At conditional (2): "i < nfonts" taking true path
At conditional (4): "i < nfonts" taking false path

6669          for (i = 0; i < nfonts; ++i)

At conditional (3): "font_scalable_p != 0" taking false path

6670            if (font_scalable_p (fonts + i))
6671              {
6672                if (better_font_p (specified, fonts + i, best, 0, 0)
6673                    || (!non_scalable_has_exact_height_p
6674                        && !better_font_p (specified, best, fonts + i, 0, 
0)))
6675                  {
6676                    non_scalable_has_exact_height_p = 1;
6677                    best = fonts + i;
6678                  }
6679              }
6680    

At conditional (5): "needs_overstrike != 0" taking true path

6681          if (needs_overstrike)
6682            {
6683              enum xlfd_weight want_weight = specified[XLFD_WEIGHT];

Event var_deref_op: Variable "best" tracked as NULL was dereferenced.
Also see events: [var_compare_op]

6684              enum xlfd_weight got_weight = best->numeric[XLFD_WEIGHT];
6685    
6686              if (want_weight > XLFD_WEIGHT_MEDIUM && want_weight > 
got_weight)
6687                {
6688                  /* We want a bold font, but didn't get one; try to use
6689                     overstriking instead to simulate bold-face.  However,
6690                     don't overstrike an already-bold fontn unless the
6691                     desired weight grossly exceeds the available weight.  
*/
6692                  if (got_weight > XLFD_WEIGHT_MEDIUM)
6693                    *needs_overstrike = (got_weight - want_weight) > 2;
6694                  else
6695                    *needs_overstrike = 1;
6696                }
6697            }
6698        }
6699    
6700      /* We should have found SOME font.  */
6701      if (best == NULL)
6702        abort ();
6703    
6704      if (font_scalable_p (best))
6705        font_name = build_scalable_font_name (f, best, pt);
6706      else
6707        font_name = build_font_name (best);
6708    
6709      /* Free font_name structures.  */
6710      free_font_names (fonts, nfonts);
6711    
6712      return font_name;
6713    }
6714