Newsgroups: comp.sys.apple2
Path: utzoo!utgpu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca!neufeld
From: neufeld@aurora.physics.utoronto.ca (Christopher Neufeld)
Subject: Re: Orca/C Bug?
Message-ID: <1991Mar10.003000.13347@helios.physics.utoronto.ca>
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Nntp-Posting-Host: aurora.physics.utoronto.ca
Organization: University of Toronto Physics/Astronomy/CITA
References: <9103081247.AA24460@apple.com>
Date: Sun, 10 Mar 1991 00:30:00 GMT

   Another one which got me for several hours last night: I have main(),
which passes by value to a subroutine, which passes that same value to
yet another subroutine, which writes it to a file with fwrite(). The
bytes being written to the file were just plain wrong until I made a
change to the savedata() routine:

doesn't work:
void savedata(a,b,c,...,g)
int a;
double b,c,**d,**e, etc.
{
  [ fopen ]
  fwrite (&b,sizeof(b),1,file);
  .....
  return;
}


It does work when I make the following change:
[ as before ]
{
  double hold;

  [ fopen ]
  hold = b;
  fwrite (&hold,sizeof(hold),1,file);
  ....
  return;
}

   It looks like the pointer to a passed parameter isn't properly
defined. It writes the integer properly, and has no trouble with the
**double types, but double gets weird.
   A possibly related problem is that the 'variables' window in the
debugger under Prizm, on the rare occasions that I use it, will not
display the value of some variables passed as double, printing **.***
instead, though the variables evaluate properly in algebraic equations.
It seems that functions which explicitly make use of the pointer mess
up, while those which use the value don't have trouble.


-- 
 Christopher Neufeld....Just a graduate student  | Note: new host.
 neufeld@aurora.physics.utoronto.ca    Ad astra! | helios will still
 cneufeld@{pnet91,pro-cco}.cts.com               | forward my mail to
 "Don't edit reality for the sake of simplicity" | me on aurora.