Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: what the heck is "reentrant"?
Message-ID: <8269@brl-smoke.ARPA>
Date: 29 Jul 88 21:58:40 GMT
References: <650002@hpcilzb.HP.COM>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 14

In article <650002@hpcilzb.HP.COM> tedj@hpcilzb.HP.COM (Ted Johnson) writes:
>What the heck is the definition of "reentrant" vs. "non-reentrant",
>for subroutines and programs?

A reentrant routine can be interrupted in the midst of operation,
reinitiated on behalf of the interrupt-processing thread of
execution, then resumed at the point of interruption with neither
invocation broken by the other.  A non-reentrant routine can't.

There is also the concept of "serially reusable" which means that
the routine can be executed from start to finish more than once
with no coupling between the invocations.  Most C functions are
written to be serially reusable; they don't modify data having
static storage duration.