[Issue 12923] UTF exception in stride even though passes validate.

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12923

Dmitry Olshansky <dmitry.olsh at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |https://github.com/D-Progra
                   |                            |mming-Language/phobos/pull/
                   |                            |2376
                 CC|                            |dmitry.olsh at gmail.com
           Assignee|nobody at puremagic.com        |dmitry.olsh at gmail.com

--- Comment #3 from Dmitry Olshansky <dmitry.olsh at gmail.com> ---
(In reply to Timothee Cour from comment #2)
> (In reply to Timothee Cour from comment #1)
> > (In reply to Timothee Cour from comment #0)
> > > import std.utf;
> > > void main(){
> > >   char[3]a=[167, 133, 175];
> > >   validate(a);
> > >   //passes
> > > 
> > >   auto k=stride(a,0);
> > >   /+
> > >   std.utf.UTFException at std/utf.d(199): Invalid UTF-8 sequence (at index 0)
> > >   pure @safe uint std.utf.stride!(char[3]).stride(ref char[3], ulong) + 141
> > >   +/
> > > }
> > > 
> > > This happens even after applying the fix
> > > https://github.com/D-Programming-Language/phobos/pull/2038
> > 
> > Additionally, another error is thrown on any of those:
> > foreach (i, dchar c; a){} //src/rt/util/utf.d:290 Invalid UTF-8 sequence
> > foreach_reverse (i, dchar c; a){} //src/rt/aApplyR.d:511 Invalid UTF-8
> > sequence
> > 
> > so perhaps std.utf.validate accepts some invalid UTF sequences
> 
> 
> Here's one possible fix:
> 
> in decodeImpl:
> ----
> UTFException invalidUTF(){...}
> 
> //insert this
> import core.bitop;
> immutable msbs = 7 - bsr(~fst);
> if (msbs < 2 || msbs > 6) throw invalidUTF();
> 
> UTFException outOfBounds() {...}
> ----
> 
> To have same behavior as inside strideImpl.
> But is that correct, or was the behavior in strideImpl wrong itself?

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