Xref: news2.mv.net comp.os.msdos.djgpp:5075
From: Eric NICOLAS <nicolas AT dsys DOT ceng DOT cea DOT fr>
Newsgroups: comp.os.msdos.djgpp
Subject: Pbs with C++ exceptions
Date: Mon, 17 Jun 1996 08:59:59 +0200
Organization: Commissariat a l'energie atomique
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To: djgpp AT delorie DOT com
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Hi djgpp gurus !

Using: djgpp v2, first non-beta release

I have some problems with C++ exceptions handling. First if I compile
a C++ program (for example test.cc) which use try/throw/catch, the
compiler answers that exception handling is disable and that I must
use -fhandle-exceptions to enable it. This flag is not documented
in the info files for gcc. strange.

Then If I have two exceptions classes A and B, with B deriving from
A, I should be able to catch exceptions B with a catch(A), no ? (I read
that in the strousup's book).

So here is a simple test program I wrote :

----- test.cc ----------------------------------------------
#include <stdlib.h>
#include <stdio.h>

class CException {};
class CSpecialException : public CException {};
class CAnotherException : public CException {};

void terminate()
{ }

int main()
{	// --- CSpecialException
	puts("Test : Throwing a CSpecialException...");
	puts("-> Should catch the CSpecialException.");
	try {
		throw CSpecialException();
	}
	catch(CSpecialException)
	{	puts("CSpecialException catched");
	}
	catch(CException)
	{	puts("CException catched");
	}
	catch(...)
	{	puts("Other exception catched");
	}
	// --- CException
	puts("\nTest : Throwing a CException...");
	puts("-> Should catch the CException.");
	try {
		throw CException();
	}
	catch(CSpecialException)
	{	puts("CSpecialException catched");
	}
	catch(CException)
	{	puts("CException catched");
	}
	catch(...)
	{	puts("Other exception catched");
	}
	// --- CAnotherException
	puts("\nTest : Throwing a CAnotherException...");
	puts("-> Should catch the CException.");
	try {
		throw CAnotherException();
	}
	catch(CSpecialException)
	{	puts("CSpecialException catched");
	}
	catch(CException)
	{	puts("CException catched");
	}
	catch(...)
	{	puts("Other exception catched");
	}
}
-----------------------------------------------------------

I compiled it with "gcc -x c++ -fhandle-exceptions test.cc -o test".

As strousup said, the result should be :
> Test : Throwing a CSpecialException...
> -> Should catch the CSpecialException.
> CSpecialException catched
> 
> Test : Throwing a CException...
> -> Should catch the CException.
> CException catched
> 
> Test : Throwing a CAnotherException...
> -> Should catch the CException.
> CException catched

But it is in fact :
> Test : Throwing a CSpecialException...
> -> Should catch the CSpecialException.
> CSpecialException catched
> 
> Test : Throwing a CException...
> -> Should catch the CException.
> CException catched
> 
> Test : Throwing a CAnotherException...
> -> Should catch the CException.
> Other exception catched
			<======= ??????

Does anybody have an explanation ???

Thanks.

-- 
Eric Nicolas <nicolas AT dsys DOT ceng DOT cea DOT fr>

Take a look to the SWORD home page :
	france:	http://bunny.ensea.fr/Pages_Perso/Cedric_Joulain/sword.web/home.html
	us:	http://www.iquest.net/~cworley/sword.web/home.html