What about errno==0 ?

[Bjoern Kriews]

Hi !

I am want to let my code now whether a routine returning NULL on failure
failed because of an I/O Error are for a logical mistake. For example,
I'm setting a global variable = errno after a failed malloc(), then do
an fclose() and return. I want to set this global to zero if the code
failed because of any error not setting errno. 

My question is:
What does the standard say about the value 0 for errno ?
Can I assume that there is no errno.h defining any errorcode = 0 ?

Any help appreciated,
  Bjoern

--
bkr at mcshh.hanse.de - Bjoern Kriews / Stormsweg 6 / 2000 Hamburg 76 / W-Germany