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Re: Pre-RFC: New C API for converting from UTF-8 to code point

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June 30, 2022 00:13
Re: Pre-RFC: New C API for converting from UTF-8 to code point
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Karl Williamson <> wrote:
:On 6/28/22 20:27, wrote:
:> Karl Williamson <> wrote:
:> :  Then the loop innards would look like:
:> :
:> :     while (s < e) {
:> :         code_point = next_uvchr(s, e, &retlen);
:> :
:> :         if (retlen < 0) {
:> I'd recommend making this `if (retlen <= 0) {` or otherwise handling
:> the retlen == 0 case, even if you only expect that when s >= e: the
:> function should be capable of doing something reasonable on an empty
:> string, which probably means not croaking.
:> :             ... process error ...
:> :             retlen = -retlen;
:> :         }
:It is currently illegal to call the existing functions with zero length 
:input.  The functions don't now croak on zero length input, but they do 
:assert against it, which on DEBUGGING builds is pretty much the same thing.

Ok, let's hope module writers habitually develop with a debug build.

And in another reply:
:The main difference would be that the return code doesn't have to be
:disambiguated.  Right now you can't tell whether the input was a NUL
:character or an error, without testing each return.  cpan modules don't
:tend to do this, leaving them vulnerable.  This API is so that you can
:be naive and still be safe.

How naive do you want? Anyone that fails to check for negative retlen
can fail quite unsafely.

I think we've established in previous discussion that you are more
comfortable with this sort of overloaded interface than I am, so I
do not wish to belabour the point. But this does rather remind me of, where pretty much every
use of grok_atou in core was buggy. I do recommend reading through
that discussion again to see if there's stuff worth learning that
could be applicable to this API.


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