> On 9/28/06, Paul Stoeber <[EMAIL PROTECTED]> wrote:
> > Should a userland program be allowed to depend on errno==0 on entry
> > to main()? (At least one in the tree does.)
>
> checking errno is the wrong way to ascertain whether a function had a
> problem, so this shouldn't be a problem for a well written program.
>
> on the other hand, code running before main is outside the scope of C
> standard, and i think the standard at least implies errno should be 0
> on entry, so we should fix/verify that too.
there is an even easier way to look at this:
errno is only valid if something indicates that you should
be checking it
some functions are documented & defined so that when they return NULL,
errno is set.
some functions are documented & defined so that when they return -1,
errno is set.
if a function has not indicated that errno is now valid, then errno contains
some previous result code which is absolutely irrelevant.
so fundamentally, the question being asked by the original poster is
"can i check what is in errno whenever i want" has a simple answer: no.
therefore it is irrelevant what value is currently stored in errno.
if nothing told you to look at it, don't look at it.
