From: Eli Zaretskii <eliz@gnu.org>
To: Andreas Schwab <schwab@linux-m68k.org>
Cc: 18995@debbugs.gnu.org, haroogan@gmail.com
Subject: bug#18995: Error: Could not reserve dynamic heap area.
Date: Sun, 09 Nov 2014 18:47:00 +0200 [thread overview]
Message-ID: <834mu8pbi3.fsf@gnu.org> (raw)
In-Reply-To: <87vbmoqqua.fsf@igel.home>
> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: eliz@gnu.org, haroogan@gmail.com
> Date: Sun, 09 Nov 2014 17:30:21 +0100
>
> Eli Zaretskii <eliz@gnu.org> writes:
>
> > Given that, it is justified for GCC to give us what we deserve, i.e. a
> > loop "unrolled" by executing its body only once. I present the
> > disassembly below, for the curious, and it's clear that there's no
> > loop there, and also the value of 'size' is never tested at all, since
> > GCC decided that the condition 'size > 0x00100000' is always true.
>
> But if you replace 'size > 0x00100000' with true, you get a loop that is
> conditionalized by '!ptr', which depends on the execution of the loop
> body. Why would it be correct to execute the loop only once,
> unconditionally?
Feel free to report this as a GCC bug, if you think that's what it is.
All I can tell is that the same behavior is present in 3 different GCC
releases from 3 different major versions.
In any case, I think the original code had a subtle bug, in that the
comparison of 'size' didn't do what the author intended.
next prev parent reply other threads:[~2014-11-09 16:47 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-08 15:22 bug#18995: Error: Could not reserve dynamic heap area Alexander Shukaev
2014-11-08 17:29 ` Eli Zaretskii
2014-11-08 18:17 ` Alexander Shukaev
2014-11-08 18:30 ` Eli Zaretskii
2014-11-08 18:40 ` Alexander Shukaev
2014-11-08 18:57 ` Eli Zaretskii
2014-11-08 19:16 ` Alexander Shukaev
2014-11-08 19:50 ` Eli Zaretskii
2014-11-08 19:58 ` Alexander Shukaev
2014-11-08 20:05 ` Eli Zaretskii
2014-11-08 20:49 ` Daniel Colascione
2014-11-09 16:12 ` Eli Zaretskii
2014-11-09 16:30 ` Andreas Schwab
2014-11-09 16:47 ` Eli Zaretskii [this message]
[not found] ` <545F94E4.5060102@dancol.org>
2014-11-09 16:30 ` Alexander Shukaev
[not found] ` <837fz4pc4o.fsf@gnu.org>
2014-11-09 16:40 ` Daniel Colascione
2014-11-09 16:35 ` Andreas Schwab
2014-11-09 16:39 ` Alexander Shukaev
2014-11-09 16:49 ` Eli Zaretskii
2014-11-09 16:53 ` Alexander Shukaev
2014-11-09 17:17 ` Eli Zaretskii
2014-11-09 17:14 ` Eli Zaretskii
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