bug#53333: Fix for crash in ebrowse

[Jan Stranik via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>
> Thanks, but can you explain the need for this part:
>
>> !           else {
>> !               s++;
>> !               break;
>> !           }
>> !       }
>
> Why do we need to advance the pointer 's' in the 'else' clause? why
> not leave it alone?

The identifier is copied from end to the buffer. As we are copying, we
want to escape quote and backslash characters. Normally if we encounter
any of these characters we just prepend \ to in front. If there is not
enough space in the buffer to insert the \, we should increase the s, to
back-out the character that we wanted to escape.

If we would not do that, the first character might not be escaped. If
that character were a quote, it would break the lisp expressions written
later to the BROWSE file.

> Or maybe I will understand the reason if you show some simple code
> that hits this problem (which would be a good thing of its own, as
> we'd then have a test to add to our test suite)?

I encountered this in a c++ header file with very long identifiers that
just filled the buffer but the first character had to be escaped.

-- 

Jan Stranik