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Date: Sat, 23 Feb 2002 04:37:27 +0100
From: Edgar Toernig <froese@gmx.de>
MIME-Version: 1.0
To: Dan Aloni <da-x@gmx.net>
CC: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] [PATCH] C exceptions in kernel
In-Reply-To: <1014412325.1074.36.camel@callisto.yi.org>
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Dan Aloni wrote:
> 
> The attached patch implements C exceptions in the kernel,

Bad idea ...

> which *don't* depend on special support from the compiler.

... which can be implemented in simple ANSI-C.  See below.

Ciao, ET.
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#include <setjmp.h>

struct _catch
{
    struct _catch *next;
    jmp_buf buf;
};

static struct _catch _catch_top[1];
struct _catch *_catch = _catch_top;

#define throw()				\
    do {				\
	_catch = _catch->next;		\
	longjmp(_catch->buf, 1);	\
    } while (0)


#define try				\
    if (setjmp(_catch->buf) == 0) {	\
	struct _catch _catch_new[1];	\
	_catch_new->next = _catch;	\
	_catch = _catch_new;

#define catch \
	_catch = _catch->next;		\
    } else


/**** example below ****/

#include <stdio.h>

int a = 1;

void
foo(int x)
{
    a=2;
    if (x & 1)
	throw();
}

int
main(int argc, char **argv)
{
    int i;

    for (i = 0; i < 10; ++i)
    {
	a=i;
	try
	{
	    try foo(i); catch
	    {
		printf("2: caught at %d (a=%d)\n", i, a);
		if ((i&3)==1)
		    throw();
	    }
	}
	catch
	{
	    printf("1: caught at %d (a=%d)\n", i, a);
	}
	printf("a=%d\n", a);
    }
    return 0;
}


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