There are better more clear ways to achieve this than fallthrough.

Cheers,
Jeremy

On Thu, Jul 3, 2025 at 04:55 Frederick Virchanza Gotham via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> I use "if else ladders" a fair bit in my code. Here's code that I'm
> looking at right now:
>
> if ( 7u == p.size() ) // P1234R0
> {
> // fall through
> }
> else if ( isdigit(p[7]) ) // length is >= 8
> {
> rev *= 10u;
> rev += (p[7]-'0');
> if ( (p.size() > 8u) && ('\0' != p[8]) && ('.' !=
> p[8]) ) break; // P1234R15
> // fall through
> }
> else if ( ('\0' == p[7]) || ('.' == p[7]) ) // length is
> >= 8
> {
> // fall through
> }
> else // length is >= 8
> {
> break;
> }
>
> Sometimes in an "if else ladder", you want to enter one of the code
> blocks, but if something goes wrong in that code block, you want to
> jump back out of it and continue down the ladder. So maybe "goto
> else;" could be used for this? The above code could become:
>
> unsigned index = 7u;
> if ( 7u == p.size() ) // P1234R0
> {
> // fall through
> }
> else if ( isdigit(p[7]) ) // length is >= 8
> {
> rev *= 10u;
> rev += (p[7]-'0');
> if ( p.size() > 8u )
> {
> ++index;
> goto else;
> }
> // fall through
> }
> else if ( ('\0' == p[index]) || ('.' == p[index]) )
> // length >= 8u
> {
> // fall through
> }
> else // length >= 8u
> {
> break;
> }
>
> This would greatly simplify some of the most complicated "if else ladders".
>
> And I actually think we should have something similar for 'catch'
> ladders, so that we can do:
>
> catch( std::exception const &e )
> {
> cout << e.what() << endl;
> goto catch; // continues down the ladder
> }
> catch(...)
> {
> cout << "An exception was thrown\n";
> }
>
> So if an exception of type "std::exception" is thrown, it enters the
> first catch handler, and then enters the second catch handler also.
> --
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