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Path: utzoo!dciem!nrcaer!cognos!geovision!alastair
From: alastair@geovision.UUCP (Alastair Mayer)
Newsgroups: comp.lang.c
Subject: Re: pre#defined cpp symbols
Message-ID: <125@geovision.UUCP>
Date: Tue, 4-Aug-87 10:10:34 EDT
Article-I.D.: geovisio.125
Posted: Tue Aug  4 10:10:34 1987
Date-Received: Sat, 8-Aug-87 07:21:30 EDT
References: <1836@zaphod.UUCP> <165600004@uiucdcsb> <657@hsi.UUCP>
Reply-To: alastair@geovision.UUCP (Alastair Mayer)
Organization: Geovision Corporation, Ottawa, Canada
Lines: 29
Summary: 'strings' won't find short strings

In article <657@hsi.UUCP> stevens@hsi.UUCP (Richard Stevens) writes:
 >> 
 >> A useful way of finding out what is defined (if you're on a Unix
 >> system) is to run `strings /lib/cpp`.  Usually they are all grouped
 >> together.
 >> 
 >
 >I've tried using strings to find these and it doesn't always seem to
 >work.  For example, 'strings /lib/cpp | grep vax' on a 4.3 system
 >won't show 'vax' as being predefined, but it is.  Looking at the source
 >for cpp shows that both "vax" and "unix" are put into the symbol table
 >the same way.
 >
 >Also, I was just trying to find all the predefined symbols under SCO Xenix
 >using strings and none of the 'M_I86xM' symbols show up, yet they are defined.
 >
 >Anyone know why ??

I don't know why strings wouldn't find 'M_I86xM' symbols, but it won't
find "vax" or any other short identifier because the algorithm strings
uses is to search for sequences of *four* or more printable characters.
You could change strings (or write your own) to look for fewer characters,
but the tradeoff is the signal to noise ratio, getting garbage sequences
of bytes that just happen to look like characters.
-- 
 Alastair JW Mayer     BIX: al
                      UUCP: ...!utzoo!dciem!nrcaer!cognos!geovision!alastair

(Why do they call it a signature file if I can't actually *sign* anything?)