RE: socket api question - is it possible for recv() to receive 0byte from server?

[Vernon Hamberg <vhamberg@xxxxxxxxxxx>]

Why? Because it is the generally accepted recommendation - as stated 
by Jon Paris as follows in his "Who Knew You Could..." redbook:

The error code is made available by the GetErrNo() function, which is a
remapped __error() C function. The GetErrNo() function gets access to the ErrNo
variable through a pointer. The ErrNo variable contains the error code. Before
issuing any function that returns an error code, the ErrNo variable should be
cleared. However, it is possible only after the GetErrNo() function 
was performed.
If the error code is not cleared before the function is entered, the 
resulting error
code may be false.

errno - as I know you know - is a global variable used by everything 
- it is not changed if not error occurs, so setting it to 0 just 
before a function that might set it and then checking it after is how 
I understand doing this.

Not all functions return an error code - an example is StrToD - it 
returns a float value - it is commonly used to test whether a string 
is numeric - the only reliable test for errors is to set errno - the 
global variable - before calling StrToD and then checking it after the call.

Tightly coupling the setting and checking will not cause problems 
with other functions, as far as I know.

Regards
Vern

At 08:40 PM 11/19/2006, you wrote:


> I consider setting errno to zero to be a bad practice. You risk screwing
> up other routines when you set it to zero. You also risk getting "false
> alarms" when you use it to determine if something failed.
>
> It's not rocket science.  Each API returns a value to tell if you if it
> succeeded or failed -- use THAT VALUE to determine if it failed.  Use
> errno to get a description of the last error (from any routine) that
> failed.
>
> Why do people insist on doing this another way?!
>
> --
> Scott Klement  http://www.scottklement.com
>
>
> On Fri, 17 Nov 2006, Vernon Hamberg wrote:
>
> > Scott
> >
> > As you say, functions that set errno do not change it if they end
> > successfully. That is why it is good practice in C to set it to 0
> > before any call to such a function. I have been able to set errno in
> > RPG - just need to call the geterrno() function (I think) to retrieve
> > it the first time, so that the pointer is set to the location of
> > errno. After that, the variable based on the pointer to errno can be
> > set to 0. Least it has worked for me - i've tried to learn my lessons
> > about pointers from you!!
> >
> --
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