Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!comp.vuw.ac.nz!windy!sramtrc
From: sramtrc@windy.dsir.govt.nz
Newsgroups: comp.unix.aux
Subject: Why doesn't this simple two line program work ...
Keywords: write stdout trap 0
Message-ID: <18794.2783c5b2@windy.dsir.govt.nz>
Date: 4 Jan 91 00:00:50 GMT
Reply-To: sramtrc@albert.dsir.govt.nz
Organization: DSIR, Wellington, New Zealand
Lines: 34


Here is a simple program that works fine when the value 20 is replaced by a
smaller integer. But when 20 or more lines are printed the program does not
do anything - it just hangs forever.

main()
{
    register int j;

    for (j = 0; j < 20; j++)
	write(1, "Why doesnt this program work for 20?\n", 37);
}


Pretty simple program huh? It is shorter than the commands to compile and link
it.  It is linked to run under A/UX in the MacOS environment (naturally it
runs fine as a pure UNIX program).

cc -I/usr/include/mac -B /usr/lib/big/ -O -DAUX -c main.c
ld /usr/lib/maccrt0.o /lib/crt2.o main.o /usr/lib/low.o -lmac_s -lld -lmr \
-lc_s  /lib/crtn.o /usr/lib/low.ld

I have played with this one for days and I can't figure it out. MacsBug shows
that it hangs at the trap 0 that is used for the write system call. One way to
get it to work for some cases is to pipe the output somewhere eg a.out | cat,
but more complicated programs print nothing when this method is used (even
though they don't hang). I have played with all sorts of initialisation stuff
like noEvents = 1, InitWindows() InitGraf() and stuff like that but to no avail.

What am I doing wrong?

Cheers,
Tony Cooper
sramtrc@albert.dsir.govt.nz