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Date:	Fri, 31 Oct 2008 12:17:22 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: canonicalize_file_name
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On Oct 31 07:03, Mark J. Reed wrote:
> John Emmas> Calling 'canonicalize_file_name(path)' is equivalent to calling
> JE> 'realpath(path, NULL)'   By a stroke of luck, 'realpath()' is defined in
> JE> cygwin/stdlib.h so maybe I should use that?
> 
> Corinna Vinschen> Yes, sure.
> 
> Yes, you should use realpath(), but passing it NULL won't necessarily
> work.  The second argument is supposed to be a pointer to the buffer
> in which it should put its result, and according to POSIX the call
> should fail if that argument is NULL.
> 
> GNU has extended its version of realpath() to dynamically allocate a
> result buffer when the second argument is NULL.  I would not assume
> that Cygwin does likewise, since it's a libc function and Cygwin
> doesn't use GNU libc.

Cygwin follows the GNU extension here.  NULL as second pointer
results in realpath returning a mallocated buffer.

>   The safest course would be to declare or
> preallocate a buffer of size PATH_MAX and pass it to realpath(); that
> should work with any POSIX-compliant C library.

Neverthless this is good advice if portability is an issue.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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