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Date: Fri, 3 May 1996 07:48:50 -0400 (EDT)
From: Richard Toren <rpt@miles.sso.loral.com>
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To: freebsd-hackers@freebsd.org
Subject: Re: stdio problem
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  The "assumption" that 'fd 0 == stdin at entry to main()' is no longer 
valid! 

In the classes I teach here at work, this is one of the examples I use 
about how old shortcuts/standards make for non-portable code and insidious 
bugs.

I learned this from first-hand experience where fileno(stdin) did not 
equal 0 but rather 1. And this was a program started from the standard 
csh command line.

This happens when a C++ static initializer procedure opens a file before 
the crt0.o (or it's C++ equivelant) has yet run. In this case, 
std{in,out,err} are fds n+0, n+1, n+2.

The bottom line is "use the system's services to identify the associated 
fd for stdin and everything else". Times are changing, any good program 
will eventually be ported somewhere else, and yesterdays assumption will 
eventually be wrong someday.

                         ====================================================
Rip Toren               | The bad news is that C++ is not an object-oriented |
rpt@miles.sso.loral.com | programming language. .... The good news is that   |
                        | C++ supports object-oriented programming.          |
                        |    C++ Programming & Fundamental Concepts          |
                        |     by Anderson & Heinze                           |
                         ====================================================