Re: readv() return and errno

[Alex Riesen <Alexander.Riesen@synopsys.com>]

On Fri, Mar 15, 2002 at 01:54:26PM -0800, Jim Hollenback wrote:
>  In doing some testing on the project I'm working on I came
>  across something that is causing a bit of confusion on my part.
> 
>  According to readv(2) EINVAL is returned for an invalid
>  argument.  The examples given were count might be greater than
>  MAX_IOVEC or zero. The test case I am working with has count = 0
>  and I get return of 0 and errno 0 instead of the expected -1
>  and errno EINVAL.
> 
>  Am I missing something?

http://www.opengroup.org/onlinepubs/007904975/
"The Open Group Base Specifications Issue 6", IEEE Std 1003.1-2001:

 The readv() function may fail if:

 [EINVAL]
 The iovcnt argument was less than or equal to 0, or greater than {IOV_MAX}.

Notice the "may"? From the same document:

 may

 Describes a feature or behavior that is optional for an implementation
 that conforms to IEEE Std 1003.1-2001. An application should not rely on
 the existence of the feature or behavior. An application that relies on
 such a feature or behavior cannot be assured to be portable across
 conforming implementations.

 To avoid ambiguity, the opposite of may is expressed as need not,
 instead of may not.
    
So the 0 there just mean nothing, exactly what you get.
 
-alex