Re: Proposal: A block between "try" and "catch".

From:
Tony Delroy <tony_in_da_uk@yahoo.co.uk>
Newsgroups:
comp.lang.c++.moderated
Date:
Tue, 10 Jun 2008 00:57:47 CST
Message-ID:
<a2210f52-dda3-4bc7-804f-663c7bca86cd@26g2000hsk.googlegroups.com>
On Jun 10, 10:24 am, Seungbeom Kim <musip...@bawi.org> wrote:

[ discussing potential notations for turning off exception catching... ]

To avoid these problems, a better syntax would be something that puts a
"try ends here" or "no catch from here" mark *inside* the try block.
For example:

     try {
         My_object obj;

     default: // no catching from here
         obj.foo();
         obj.bar();
     }
     catch (My_exception& ex) {
         // ...
     }

Or another syntax could be a block inside, like this:

     try {
         My_object obj;

         try void { // exceptions not caught
                         // "try void"? "void try"? "try = 0"? ...
             obj.foo();
             obj.bar();
         }

         obj.qux(); // exceptions caught
     }
     catch (My_exception& ex) {
         // ...
     }


These notations still affect all types of exceptions: if bothering to
make a change to address this issue at all, the solution might as well
permit more fine grained control. Further: how many surrounding try/
catch scopes should these notations implicitly throw past? Why limit
it to one? Having said that, simply giving a number would lead to
very fragile code (like some languages "break N" scopes) if those
scopes aren't within the function, as a function shouldn't have to be
aware of its callers. So, I still think a "goto" approach is a
reasonable compromise - yes any goto is ugly, but then it's clearly an
unusual situation already if the exception handling is this fiddly.
To extend my previous suggestion:

try { ... } throw goto X;
   rethrows anything from label X

try { ... } catch (const T&) { throw goto X; } ...
   rethrow the T from label X, other catch statements allowed in catch
list...

Regards,

Tony

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