Date: Wed, 26 Apr 1995 09:19:10 -1000
From: Jim Thomas <thomas AT cfht DOT hawaii DOT edu>
To: tony AT nt DOT tuwien DOT ac DOT at
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: exit()

Tony> I just had some troubles with exitcodes:

Tony> I left a program, called with a spawnlp() from a second program, with
exit(-2). The result was that spawnlp() returned 254.

Tony> Code:
.....

>From the docs:

Tony> void volatile exit(int exit_code);
Tony> and
Tony> int spawnlp(...)

Tony> That means both, the parameter of exit() and the return value of
Tony> spawnlp() are int.

Tony> I remember having read long time ago that DOS can only handle errorcodes
Tony> 0...255.
Tony> (is that correct ?) Therefore it is not a DJGPP but a DOS problem.

Tony> I finally declared 

Tony> signed char en;

Tony> and got corrrect behavior for negative exitcodes. 

Tony> This is just a workaround. What is the correct procedure to deal with
Tony> exitcodes (in a portable way) ?

In spite of the "int exit_code" declaration, to be portable, the exit codes
should be treated as unsigned char .  This is what unix(tm) uses.  (I know,
I've just been through the same exercise :-)  Some unix shells seem to
pretend that the exit codes are int's.  But "the low order 8 bits of
exit_code are made available to the parent process".  The implication could
be that "signed char" is reasonable as long as one remembered that the
range is -128 through 127.  The implication of the DOS 0 through 255 is
that it really should be considered unsigned.

Jim