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bug#8215: possibly uninitialized variable lower_xoff in produce_glyphles
From: |
Eli Zaretskii |
Subject: |
bug#8215: possibly uninitialized variable lower_xoff in produce_glyphless_glyph |
Date: |
Wed, 02 Jun 2021 16:17:11 +0300 |
> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Wed, 02 Jun 2021 10:06:29 +0200
> Cc: 8215@debbugs.gnu.org, Kenichi Handa <handa@m17n.org>
>
> Paul Eggert <eggert@cs.ucla.edu> writes:
>
> > In the meantime, I plan to work around the problem by initializing
> > lower_xoff to 0, with a FIXME explaining the situation: this shouldn't
> > introduce a bug, because at worst it will replace undefined behavior
> > with defined behavior.
>
> It looks like this code is still in place now, ten years later:
>
> diff --git a/src/xdisp.c b/src/xdisp.c
> index 44cb713011..44a317b578 100644
> --- a/src/xdisp.c
> +++ b/src/xdisp.c
> @@ -22292,7 +22292,13 @@ produce_glyphless_glyph (struct it *it, int
> for_no_font, Lisp_Object acronym)
> if (metrics_upper.width >= metrics_lower.width)
> lower_xoff = (width - metrics_lower.width) / 2;
> else
> - upper_xoff = (width - metrics_upper.width) / 2;
> + {
> + /* FIXME: This code doesn't look right. It formerly was
> + missing the "lower_xoff = 0;", which couldn't have
> + been right since it left lower_xoff uninitialized. */
> + lower_xoff = 0;
> + upper_xoff = (width - metrics_upper.width) / 2;
> + }
> }
>
> /* +5 is for horizontal bars of a box plus 1-pixel spaces at
>
> Anybody have any insight into whether this is correct or not now?
I fixed this (and removed the FIXME with the incorrect
initialization). Bottom line: it was a typo.