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Date: Wed, 14 Jun 2023 14:20:02 +0200
To: <cygwin@cygwin.com>
Subject: fork bug in cygheap
Message-ID: <b7a37aeabe4ce0df6b33f55088a28150@tiscali.it>
From: Paolo via Cygwin <cygwin@cygwin.com>
Reply-To: paolo.zambotti@tiscali.it
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  Hi all,

I just found a bug (I think) in cygheap_fixup_in_child
function (cygheap.cc).
the effect is that, sometimes a command from a
script ends with the following error message

0 [main] openssl (17784)
child_copy: cygheap read copy failed, 0x0..0x8003D8538, done 0, windows
pid 17784, Win32 error 299

Digging a little bit in the code I found
that commit_size in cygheap_fixup_in_child is wrongly calculated if the
condition (child_proc_info->cygheap_max > (void *)
CYGHEAP_STORAGE_INITIAL) is met.

Currently, in that case, its value is
evaluated as

commit_size = allocsize
(child_proc_info->cygheap_max);

but I think this is wrong and it should
be

commit_size = allocsize (child_proc_info->cygheap_max) -
CYGHEAP_STORAGE_LOW;

The wrong value avoids the successful execution of
the following second VirtualAlloc and the the error in child_copy
function.

I tried to recompile the cygwin dll with the above change and
indeed the error disappears.

I'm I correct?
Paolo. 


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