Path: utzoo!attcan!uunet!image.soe.clarkson.edu!news
From: cline@cheetah.ece.clarkson.edu (Marshall Cline)
Newsgroups: comp.lang.c++
Subject: Re: Turbo-C++ problem when compiling without debugging info
Message-ID: <CLINE.90Aug13121729@cheetah.ece.clarkson.edu>
Date: 13 Aug 90 16:20:52 GMT
References: <14509@shlump.nac.dec.com>
Sender: news@sun.soe.clarkson.edu
Reply-To: cline@sun.soe.clarkson.edu (Marshall Cline)
Organization: (I don't speak for the) ECE Dept, Clarkson Univ, Potsdam, NY
Lines: 58
In-reply-to: wallis@labc.enet.dec.com's message of 12 Aug 90 21:28:24 GMT

In article <14509@shlump.nac.dec.com> wallis@labc.enet.dec.com (Barry L. Wallis) writes:
>
>The attached program exhibits some strange behavior. When compiled and linked
>with debugging information turned on (both in the IDE or on the command line)
>the prgram works fine. However, when the debugging information is turned off
>(-v- on the command line). Needless to say this makes debugging very difficult
>
>The classes #included using qutoation marks are from the Turbo-C++ class
>library. The others are the normal Turbo-C++ header files.
>
>Any ideas?

In my TC++ review in the most recent `C++ Report' (vol.2, #7, Jul/Aug 90),
I reported finding a very unusual compiler bug which behaved like this.

If you call a virtual member function from an *inline* function in a base
class, the virtual function call gets bound *statically*.  Ex:

	class Stack {
	public:
	  virtual int length() const = 0;	// Return Stack's curr `length'
	          int empty()  const { return length() == 0; }	// Is it empty?
	  //...
	};

Under the following rather special conditions, TC++ generates bad code:
 IF  * you compile it with command-line `tcc' rather than integrated `tc'.
 AND * you compile it with debugging turned off (-v-)
 AND * you compile it with inlines turned on (-vi)

The work-arounds for this are obvious.  Any one of the following will do:
    * out-line the `Stack::empty()' function
 OR * use `tc' (strange, but `tc' compiles it correctly)
 OR * use `tcc' but use -v (-v turns off inlining unless followed by -vi)
 OR * use `tcc' but use -vi-

Borland has been made aware of the bug.

Marshall Cline

PS: I have created a bug-list repository for TC++ which has work-arounds.
It's available by anonymous ftp from sun.soe.clarkson.edu [128.153.12.3]
in the file ~ftp/pub/Turbo-C++/bug-report

If you don't have ftp access, write me at my USmail address below, and
I'll USmail it to you for a $5 processing fee (sorry for the fee, but
I don't want to be inundated with requests that will cost me hours of
my time :-).

--
==============================================================================
Marshall Cline / Asst.Prof / ECE Dept / Clarkson Univ / Potsdam, NY 13676
cline@sun.soe.clarkson.edu / Bitnet:BH0W@CLUTX / uunet!clutx.clarkson.edu!bh0w
Voice: 315-268-3868 / Secretary: 315-268-6511 / FAX: 315-268-7600
Career search in progress; ECE faculty; research oriented; will send vita.
PS: If your company is interested in on-site C++/OOD training, drop me a line!
==============================================================================