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From: Brian Inglis <Brian.Inglis@SystematicSw.ab.ca>
Subject: Re: malloc(0) crashing with SIGABRT
Reply-To: Brian.Inglis@SystematicSw.ab.ca
To: cygwin@cygwin.com
References: <366918d8-b505-45be-dc28-303579f17341@gmail.com> <78e19eb7-956e-cd05-a076-e56ce347bbbe@gmail.com>
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Message-ID: <749ecff2-e384-bbfe-c961-481157c73052@SystematicSw.ab.ca>
Date: Wed, 11 Sep 2019 21:59:08 -0600
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On 2019-09-09 11:13, Petr Skočík wrote:
> There's been a twitter discussion on how different POSIX platforms
> handle malloc(0): https://twitter.com/sortiecat/status/1170697927804817412 .
> 
> As for Cygwin, the answer appears to be "not well", but this should be
> easy to fix.

POSIX SUS V4 2018 says:

"RETURN VALUE

Upon successful completion with size not equal to 0, malloc() shall return a
pointer to the allocated space. If size is 0, either:

	A null pointer shall be returned [CX] [Option Start]  and errno may be set to
an implementation-defined value, [Option End] or

	A pointer to the allocated space shall be returned. The application shall
ensure that the pointer is not used to access an object.

Otherwise, it shall return a null pointer [CX] [Option Start]  and set errno to
indicate the error. [Option End]"

The second option could be implemented by a pointer to an unmapped page, or a
reference to an inaccessible mmap-ed area length zero.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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