Message-Id: <200008011532.LAA14698@delorie.com>
Date: Tue, 01 Aug 2000 18:31:06 +0200
To: djgpp AT delorie DOT com
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From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
CC: ilari DOT liusvaara AT purkki DOT mbnet DOT fi
In-reply-to: <00CF54B.00640E1F47.uuout@purkki.mbnet.fi>
	(ilari DOT liusvaara AT purkki DOT mbnet DOT fi)
Subject: Re: Program miscompiled by GCC
References:  <00CF54B DOT 00640E1F47 DOT uuout AT purkki DOT mbnet DOT fi>
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> From: ilari DOT liusvaara AT purkki DOT mbnet DOT fi (Ilari Liusvaara)
> Date: Sun, 22 Jul 00 22:35:00 +0200
> 
>  When I compile this program with -ansi, GCC 2.7.2.1 generates program that
>  bombs and GCC 2.9.5.2 generates program that display resluts that do not
>  make sense. The comments and messages are in finnish and I don't bother to
>  translate them. I have marked the line that generates instructions that
>  bomb the program when compiled with GCC 2.7.2.1 (at least SYMIFY tells
>  that it is that line.) When I compile without -ansi, program works just
>  fine.

The bug is in your program: it doesn't declare a prototype for the
_atold function.  When the compiler sees a function that doesn't have
a prototype, it assumes that it returns an int, whereas _atold returns
a long double.  So the code bombs.

When you compile without -ansi, the prototype for _atold that is in
stdlib.h becomes visible, and everything works.  Using -ansi masks the
prototype to avoid polluting the program's namespace.  If you use the
"-Wall" switch, you will see a warning about missing prototype.

The morale is that you cannot safely compile non-ANSI programs with
"-ansi", unless you declare prototypes for all non-ANSI functions.