full-disclosure - Re: readdir_r considered harmful

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Message-ID: <200511051845.jA5IjKDk007734@vaticaan.Holland.Sun.COM>
Date: Sat Nov  5 18:48:15 2005
From: Casper.Dik at Sun.COM (Casper.Dik@....COM)
Subject: Re: readdir_r considered harmful 

>The Austin Group should amend POSIX and the SUS in one or more of the
>following ways:
>
>1.  Standardise the dirfd function from BSD and recommend its use in
>    determining the buffer size for readdir_r.
>2.  Specify a new variant of readdir in which the buffer size is explicit
>    and the function returns an error code if the buffer is too small.
>3.  Specify that NAME_MAX must be defined as the length of the longest
>    name that can be used on any filesystem.  (This seems to be what many
>    or most implementations attempt to do at present, although POSIX
>    currently specifies otherwise.)

Why not:

4. Require the readdir() implementation to use state local to dirp.

I've never understood the rationale behind readdir_r; it's like someone
went through the manual looking for "pointers to static locations"
and defined new functions with _r for each of them, suspending thinking.

But perhaps people can look at how their readdir() implementations
behave.  The Solaris implementation appears to be "unshared dirp safe".

Casper