On Mon, Dec 30, 2019 at 03:31:31PM -0800, H. S. Teoh via Digitalmars-d-learn
wrote:
> On Mon, Dec 30, 2019 at 03:09:58PM -0800, H. S. Teoh via Digitalmars-d-learn
> wrote:
> [...]
> > I suspect the cause is that whatever Grapheme.opSlice returns is
> > going out-of-scope when used with .map, that's why it's
> > malfunctioning.
> [...]
>
> Haha, it's actually right there in the Grapheme docs for the opSlice
> overloads:
>
> Random-access range over Grapheme's $(CHARACTERS).
>
> Warning: Invalidates when this Grapheme leaves the scope,
> attempts to use it then would lead to memory corruption.
>
> Looks like when you use .map over the Grapheme, it gets copied into a
> temporary, which gets invalidated when map.front returns. Somewhere
> we're missing a 'scope' qualifier...
[...]
Indeed, compiling with dmd -dip1000 produces this error message:
test.d(15): Error: returning g.opSlice() escapes a reference to
parameter g, perhaps annotate with return
/usr/src/d/phobos/std/algorithm/iteration.d(499): instantiated
from here: MapResult!(__lambda1, Grapheme[])
test.d(15): instantiated from here: map!(Grapheme[])
Not the most helpful message (the annotation has to go in Phobos code,
not in user code), but it does at least point to the cause of the
problem.
T
--
What doesn't kill me makes me stranger.
