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From: Lee_Robert_Willis@cup.portal.com
Newsgroups: comp.sys.amiga.programmer
Subject: Debugging C++
Message-ID: <42022@cup.portal.com>
Date: 5 May 91 20:40:35 GMT
Organization: The Portal System (TM)
Lines: 97

re: Comeau C++ and debugging:

Lee Willis> I'm very curious about how and to what extent SAS's CPR can 
Lee Willis> be used to debug Comeau's C++ code.  (A debugger is a _big_ 
Lee Willis> issue.  I wasn't considering buying your compiler until you 
Lee Willis> mentioned that C debuggers could be used)

Greg Comeau> Line number and source file information is retained and that is simply
Greg Comeau> accepted by the C compiler.  There is no special trick involved.

Well it sounds pretty magic to me.  If I were to create my own language
("LEE++"), and a translater ("LEEfront") which read LEE++ source code,
and spat out C source code, which was then fed through my SAS C 
compiler to produce an executable, I would not expect to be able to use
the CPR debugger to debug native LEE++ code.  CPR has no way of knowing
that the C code was an _intermediate_ form, and that LEE++ was the actual
source language.  (CPR wouldn't know LEE++ from spam)

Lee Willis> Could you post a file which contains some source code, and the
Lee Willis> compiled executable (compiled with debug) so those of us with
Lee Willis> debuggers could try it out for ourselves? 

Greg Comeau> I don't see what that would accomplish.  

For one, it might convince me to buy your product.

Greg Comeau>                          ...It is my understanding that
Greg Comeau> others here on the net have Comeau C++ and they are not 
Greg Comeau> disputing what I am saying.  

No one has confirmed it, either.  

If you think I'm confused, you're right.  The following excerpts
should explain WHY I'm confused:  

John W. Marvin> I assume there is no C++ debugger w/ Comeau?

Greg Comeau> That is currently correct, however it is worth noting that as we
Greg Comeau> currently are telling you to do something like "buy a C compiler
Greg Comeau> too", the result is that you will have a C debugger like CPR and
Greg Comeau> that works fine.   

Art Baker> Yes, but...
Art Baker> Using CPR would allow you to look at the C which resulted
Art Baker> from compiling the C++ source code.  It would not give you the
Art Baker> ability to debug at the C++ source level.  This is a
Art Baker> much-less-than-optimal solution.

Greg Comeau> Not so at all.
Greg Comeau> 
Greg Comeau> Using CPR allows you to debug/look at the C++ source
Greg Comeau> _*NOT*_ the intermediate C.

Micheal Rizzo> Another problem is that member function names of
Micheal Rizzo> the form "class::function" get translated to some other C
Micheal Rizzo> function name internally - I don't know for sure but I expect
Micheal Rizzo> this is the case with Comeau C++ (that's how its done on GNU and
Micheal Rizzo> Zortech).

Greg Comeau> That is correct.  
             ^^^^^^^^^^^^^^^^
This doesn't sound like source level debugging to me.

Greg Comeau>                  ....We find that initial purchasers of
Greg Comeau> Comeau C++ will sometimes call up about this, but often never
Greg Comeau> call twice as they get used to it since C++ has many
Greg Comeau> characteristics which diverts the energy normally spent in
Greg Comeau> debugging into other areas of the programming cycle.
Greg Comeau> Nevertheless, this is something that we spend time on solving
Greg Comeau> with the ports of Comeau C++ we do.  For instance, under UNIX we
Greg Comeau> have something called CCsdb, which allows you to use to C++ names
Greg Comeau> as is.

Micheal Rizzo> With older versions of GNU gdb there was a small utility g++filt
Micheal Rizzo> which one could use to translate between C++ and mangled
Micheal Rizzo> identifiers. Used with a mouse cut-and-paste-text-between-windows
Micheal Rizzo> as provided by xterm this was very useful. I believe such a PD
Micheal Rizzo> utility for cutting & pasting text between console windows is
Micheal Rizzo> available for the Amiga so maybe an equivalent of g++filt would
Micheal Rizzo> be nice ?

Greg Comeau> Comeau C++ comes with a utility we call c++filt, c++filt.CC, or
Greg Comeau> comofilt depending upon the port (don't ask we why haven't
Greg Comeau> standardized the name please) that supports just such a
Greg Comeau> demangling capability.

Why would one need a name-demangler if the debugger shows C++ source code?
Do you see my confusion?  Based solely on whats posted here on the net,
(which is all the information I currently have) I am forced to conclude 
that using CPR to debug C++ is going to give me (at best) some sort of 
bastard hybrid environment, where the display shows C++ sometimes, and
name-mangled C at others.

If you post some source code and compiled executables, I can see for 
myself. 

Lee		Lee_Robert_Willis@cup.portal.com