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To: djgpp AT delorie DOT com
From: "J.W. Jagersma (jwjagersma AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
Subject: malloc() returns pointer to already allocated memory
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Message-ID: <158e5d20-0a90-4beb-de48-da328379d8fb@gmail.com>
Date: Mon, 17 Jun 2019 02:27:18 +0200
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Reply-To: djgpp AT delorie DOT com

This is a multi-part message in MIME format.
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I ran into this issue with malloc(). It seems that, given enough 
allocations, malloc() will eventually return a pointer into already 
allocated memory.

The attached program is able to reproduce this rather consistently, but 
only under cwsdpmi. It also only happens if the memory has previously 
been written to (suggesting a paging issue?). However the code that 
first led me to investigate this also exhibits the same problem under 
hdpmi. As such, I'm still not entirely convinced that this initial issue 
wasn't caused by my own code. I also find it hard to believe that no one 
else noticed this rather obvious problem before me.
Still, the attached program demonstrates this clobbering issue, and I 
think this would warrant further investigation.

Any insight is much appreciated.

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