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>Return Conventions</H1
><P
> For code called in user context, it's very common to defy C
convention, and return <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> for success,
and a negative error number
(eg. <SPAN
CLASS="RETURNVALUE"
>-EFAULT</SPAN
>) for failure. This can be
unintuitive at first, but it's fairly widespread in the networking
code, for example.
</P
><P
> The filesystem code uses <TT
CLASS="FUNCTION"
>ERR_PTR()</TT
>
<TT
CLASS="FILENAME"
>include/linux/fs.h</TT
>; to
encode a negative error number into a pointer, and
<TT
CLASS="FUNCTION"
>IS_ERR()</TT
> and <TT
CLASS="FUNCTION"
>PTR_ERR()</TT
>
to get it back out again: avoids a separate pointer parameter for
the error number. Icky, but in a good way.
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