|[5 earlier articles]|
|Re: Exception Handling email@example.com (journeyman) (2002-08-04)|
|Re: Exception Handling firstname.lastname@example.org (Nick Maclaren) (2002-08-10)|
|Re: Exception Handling email@example.com (Marco van de Voort) (2002-08-10)|
|Re: Exception Handling firstname.lastname@example.org (Maxim Reznik) (2002-08-10)|
|Re: Exception Handling email@example.com.OZ.AU (Fergus Henderson) (2002-08-14)|
|Exception Handling firstname.lastname@example.org (Bernhard Tschirren) (1998-09-13)|
|Re: Exception Handling email@example.com (1998-09-18)|
|Re: Exception Handling firstname.lastname@example.org (1998-09-18)|
|Re: Exception Handling email@example.com (1998-09-18)|
|Re: Exception Handling firstname.lastname@example.org (Morten Christensen) (1998-09-26)|
|From:||email@example.com (Mike Stump)|
|Date:||18 Sep 1998 23:03:08 -0400|
|Organization:||Kithrup Enterprises, Ltd.|
Bernhard Tschirren <firstname.lastname@example.org> wrote:
>Could somebody please explain "zero runtime overhead" exception handling.
>Im only familiar with the traditional setjmp() / longjmp() methods.
>[I thought the code was instrumented with a table that the exception
>handler consulted to figure out which exception handler to use. -John]
Right, thought that may be too short for a newcomer to understand.
Imagine a table that is index by PC ranges that contains a handler to
jump to, should the PC be within that range. When compiling code, you
arrange for all code blocks to be bracketed by handlers. For a
function body, its handler unwinds the function call. When selecting
a handler, you pick the innermost handler (the tightest range).
Advantage, no inline code to manage EH variable stack, or
activations/deactivations. It is managed solely by the PC contents.
If you want to see this in action, get g++ (egcs.cygnus.com), and
compile something up. -fsjlj-exceptions will select the setjmp style
cost you will recognize, and -fno-sjlj-exceptions will select the zero
There are tons more details and various optimizations that can be
done, but you get the idea.
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