Re: master updated (05b7953 -> b2b1ccb)

[Alex Gramiak <agrambot@gmail.com>]

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Lars Ingebrigtsen <larsi@gnus.org> writes:

> This patch series seems to introduce the following warnings?
>
> xdisp.c: In function ‘normal_char_ascent_descent’:
> xdisp.c:26433:13: warning: potential null pointer dereference [-Wnull-dereference]
>     if (!(pcm->width == 0 && pcm->rbearing == 0 && pcm->lbearing == 0))
>           ~~~^~~~~~~
> xdisp.c: In function ‘gui_produce_glyphs’:
> xdisp.c:28482:15: warning: potential null pointer dereference [-Wnull-dereference]
>         if (pcm->width == 0
>             ~~~^~~~~~~
> xdisp.c:28745:16: warning: potential null pointer dereference [-Wnull-dereference]
>          if (pcm->width == 0
>              ~~~^~~~~~~

Hmm, this is weird: the warnings seem to be legitimate
(get_per_char_metric can return NULL), but I don't see how my patch
would _introduce_ these warnings.

Also, I don't get these warnings; what's your compiler version? If it's
GCC 9, perhaps the warning detection has improved. I don't suppose you
happened to update your compiler at the same time as updating your local
branch?

It's good to plug these anyway, but it would be nice to figure out why
they're only popping up now.

The below diff should silence the warnings.


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diff --git a/src/xdisp.c b/src/xdisp.c
index c561ea9e36..ca95f8f944 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -26430,7 +26430,10 @@ normal_char_ascent_descent (struct font *font, int c, int *ascent, int *descent)
 	{
 	  struct font_metrics *pcm = get_per_char_metric (font, &char2b);
 
-	  if (!(pcm->width == 0 && pcm->rbearing == 0 && pcm->lbearing == 0))
+	  if (!(pcm
+                && pcm->width    == 0
+                && pcm->rbearing == 0
+                && pcm->lbearing == 0))
 	    {
 	      /* We add 1 pixel to character dimensions as heuristics
 		 that produces nicer display, e.g. when the face has
@@ -28479,8 +28482,10 @@ gui_produce_glyphs (struct it *it)
 	  if (get_char_glyph_code (it->char_to_display, font, &char2b))
 	    {
 	      pcm = get_per_char_metric (font, &char2b);
-	      if (pcm->width == 0
-		  && pcm->rbearing == 0 && pcm->lbearing == 0)
+	      if (pcm
+                  && pcm->width    == 0
+                  && pcm->rbearing == 0
+                  && pcm->lbearing == 0)
 		pcm = NULL;
 	    }
 
@@ -28742,8 +28747,10 @@ gui_produce_glyphs (struct it *it)
 		  if (get_char_glyph_code (' ', font, &char2b))
 		    {
 		      pcm = get_per_char_metric (font, &char2b);
-		      if (pcm->width == 0
-			  && pcm->rbearing == 0 && pcm->lbearing == 0)
+		      if (pcm
+                          && pcm->width    == 0
+                          && pcm->rbearing == 0
+                          && pcm->lbearing == 0)
 			pcm = NULL;
 		    }