* bug#8211: uninitialized variable in detect_coding_iso_2022's end-of-composition code
@ 2011-03-09 17:53 Paul Eggert
2011-03-09 22:30 ` Andreas Schwab
2019-06-19 0:19 ` Paul Eggert
0 siblings, 2 replies; 3+ messages in thread
From: Paul Eggert @ 2011-03-09 17:53 UTC (permalink / raw)
To: 8211
I found this problem by compiling Emacs with GCC's -Wuninitialized flag.
The following code in the Emacs trunk src/coding.c's
detect_coding_iso_2022 function apparently uses an uninitialized variable:
...
else if (c == '1')
{
/* End of composition. */
if (composition_count < 0
|| composition_count > MAX_COMPOSITION_COMPONENTS)
/* Invalid */
break;
composition_count = -1;
found |= CATEGORY_MASK_ISO;
}
else
...
/* We found a valid designation sequence for CHARSET. */
rejected |= CATEGORY_MASK_ISO_8BIT;
if (SAFE_CHARSET_P (&coding_categories[coding_category_iso_7],
id))
found |= CATEGORY_MASK_ISO_7;
The problem is that the "else if (c == '1')" branch does not initialize
the local variable "id", but the second "if" test uses that variable.
I plan to work around the uninitialized-variable problem by initializing
"id" to zero. This will replace undefined behavior with defined behavior,
so it shouldn't introduce a new bug, but it probably doesn't fix the
bug in question, assuming there is one. Could an expert in this
area please review this and come up with a real fix?
I'm CC'ing this to Kenichi Handa, who committed the code in question.
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#8211: uninitialized variable in detect_coding_iso_2022's end-of-composition code
2011-03-09 17:53 bug#8211: uninitialized variable in detect_coding_iso_2022's end-of-composition code Paul Eggert
@ 2011-03-09 22:30 ` Andreas Schwab
2019-06-19 0:19 ` Paul Eggert
1 sibling, 0 replies; 3+ messages in thread
From: Andreas Schwab @ 2011-03-09 22:30 UTC (permalink / raw)
To: Paul Eggert; +Cc: 8211
Paul Eggert <eggert@cs.ucla.edu> writes:
> I found this problem by compiling Emacs with GCC's -Wuninitialized flag.
>
> The following code in the Emacs trunk src/coding.c's
> detect_coding_iso_2022 function apparently uses an uninitialized variable:
>
> ...
> else if (c == '1')
> {
> /* End of composition. */
> if (composition_count < 0
> || composition_count > MAX_COMPOSITION_COMPONENTS)
> /* Invalid */
> break;
> composition_count = -1;
> found |= CATEGORY_MASK_ISO;
> }
> else
> ...
>
> /* We found a valid designation sequence for CHARSET. */
> rejected |= CATEGORY_MASK_ISO_8BIT;
> if (SAFE_CHARSET_P (&coding_categories[coding_category_iso_7],
> id))
> found |= CATEGORY_MASK_ISO_7;
>
> The problem is that the "else if (c == '1')" branch does not initialize
> the local variable "id", but the second "if" test uses that variable.
I think it just lacks a break. ESC '1' is not a designation sequence.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#8211: uninitialized variable in detect_coding_iso_2022's end-of-composition code
2011-03-09 17:53 bug#8211: uninitialized variable in detect_coding_iso_2022's end-of-composition code Paul Eggert
2011-03-09 22:30 ` Andreas Schwab
@ 2019-06-19 0:19 ` Paul Eggert
1 sibling, 0 replies; 3+ messages in thread
From: Paul Eggert @ 2019-06-19 0:19 UTC (permalink / raw)
To: 8211-done
Kenichi Handa evidently fixed this old bug in 2011 after I filed it, so I'm closing the bug report now.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-03-09 17:53 bug#8211: uninitialized variable in detect_coding_iso_2022's end-of-composition code Paul Eggert
2011-03-09 22:30 ` Andreas Schwab
2019-06-19 0:19 ` Paul Eggert
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