Dart_StringToCString should be removed from the Dart API and replaced with safer equivalents

[lexprfuncall]

As Dart strings are permitted to contain an arbitrary number of U+0000 code points, it is not possible to safely and securely marshal Dart strings into C strings.

I am in the process of adding Dart_StringToBytes which takes a Dart string and returns an array of UTF-8 code units and a length. I believe this function, along with a function to compare a Dart string with an array of UTF-8 code units, should be sufficient to replace the uses of Dart_StringToCString.

[dgrove]

Added Area-VM, Triaged labels.

[whesse]

Dart_StringToCString is used very often in runtime/bin, directly and through DartUtils::GetStringValue. If it is replaced with a safer variant, which I agree is probably necessary, then a common use case will be:

Turn a Dart String into a UTF8 C null-terminated string, throwing an error if there are null characters in the Dart String.

Can we support that efficiently? Could we keep a StringToCString that returns an error if there is a null in the string?

We really need something that outputs a null-terminated string. Could StringToBytes add a null character at the end?

[iposva-google]

Why can't Dart_StringToCString just return the UTF-8 encoded string value? I understand that you could still have a NUL character in your Dart string and thus you would get a short string from the C perspective, but at least you get something that is very, very convenient from the usage perspective.

[iposva-google]

Set owner to @lexprfuncall.

[iposva-google]

Removed the owner.

[iposva-google]

Added this to the Later milestone.
Removed Priority-Medium label.
Added Priority-Low label.

[kasperl]

Removed this from the Later milestone.
Added Oldschool-Milestone-Later label.

[kasperl]

Removed Oldschool-Milestone-Later label.

[iposva-google]

We decided that the convenience trumps the concern of short C strings. Keeping this as is, returning a UTF-8 string.