Re: Valgrind is complaining unitialized values in freea (malloca.c:135)

[Tim Rühsen]

On Dienstag, 22. August 2017 06:11:41 CEST Marc Nieper-Wißkirchen wrote:
> In freea in malloca.c, a possibly uninitialized indicator word is used for
> a comparison so that Valgrind reports: "Conditional jump or move depends on
> uninitialised value(s)".
> 
> Valgrind is not smart enough to understand the logic in freea.
> 
> It would be nice if the warning could be silenced, either by amending freea
> slightly (it seems that a similar thing has already been done for Clang
> warnings) or by reporting the issue to the Valgrind developers so that they
> can special-case gnulib's freea.

I also see several false positives from clang's Undefined Sanitizer due to
alloca 'magic' (reallocations on stack space ?). This might not be directly
related, but I think there is a common coding pattern.

glob.c:1738:23: runtime error: index 64 out of bounds for type 'char *[64]'
    #0 0x557545 in glob_in_dir /home/tim/src/wget2/lib/glob.c:1738:40
    #1 0x54ded1 in rpl_glob /home/tim/src/wget2/lib/glob.c:1306:16

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior glob.c:1738:23 in
glob.c:1739:27: runtime error: index 64 out of bounds for type 'char *[64]'
    #0 0x5575d4 in glob_in_dir /home/tim/src/wget2/lib/glob.c:1739:27
    #1 0x54ded1 in rpl_glob /home/tim/src/wget2/lib/glob.c:1306:16

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior glob.c:1739:27 in
glob.c:1811:21: runtime error: index 64 out of bounds for type 'char *[64]'
    #0 0x55845e in glob_in_dir /home/tim/src/wget2/lib/glob.c:1811:21
    #1 0x54ded1 in rpl_glob /home/tim/src/wget2/lib/glob.c:1306:16

Regards, Tim

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