Date: Fri, 03 May 1996 08:42:10 -0600 From: Warner Losh <imp@village.org> To: Richard Toren <rpt@miles.sso.loral.com> Cc: freebsd-hackers@FreeBSD.org Subject: Re: stdio problem Message-ID: <199605031442.IAA09888@rover.village.org> In-Reply-To: Your message of Fri, 03 May 1996 07:48:50 EDT
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: The "assumption" that 'fd 0 == stdin at entry to main()' is no longer
: valid!
It *MUST* be valid. It is how Unix works. The *SHELL* sets these
things up, so how does one find out what to use if 0 isn't it? Using
stdio isn't an answer here, because I must be able to find this out
w/o ever touching stdio.
: 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.
When main() is entered 0, 1, and 2 are already open *BY*THE*SHELL*
that fork/exec'd the program. stdio doesn't actually do an open(2) on
0, 1, 2. It merely maps them to std* to 0, 1, 2. It has no way of
knowing what to open so must always use 0, 1, and 2. I'd be very very
surprised if you could come up with a program where fileno(stdin) !=
0. Please post it.
C++ static object constructors should be able to access stdin, et al.
Any C++ implementation that does not allow this is broken and should
be fixed.
Warner
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