1485805 - Add a JS::CompileUtf8 that compiles UTF-8 without inflating to UTF-16

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P2)

Description

[Jeff Walden [:Waldo]]

One JS::Compile function takes SourceBufferHolder.  In bug 1485800 SBH will become either UTF-8 or UTF-16, so that entrypoint will (ultimately) always parse in the most optimal way.

But the other entrypoints take either Latin-1 or UTF-8, and if we just change the guts to parse UTF-8 the natural way, we will change a whole swathe of behaviors -- IMO a little too quickly.  We want to be able to change a few things and get good feedback on correctness, then change more, then gradually opt all of SpiderMonkey and all of Gecko into using UTF-8-specific compilation wherever possible.

Separate entrypoints that *only* take UTF-8 (and do not inflate to UTF-16, as happens now for both the UTF-8 and Latin-1 cases) will allow for explicit transition to accepting UTF-8 in specific places.

While most of this bug is plumbing, I expect it will also add at least one major user of such an API or APIs -- likely in the JS shell, possibly hidden behind a command line flag to the shell (or disabled by such).

Comment 1

[Jeff Walden [:Waldo]]

This bug may be outliving its usefulness, as I do this work piecemeal in other bugs, generally as JS::CompileUtf8DontDeflate-named functions until all the bugs have been worked out of the actually-UTF-8 path.  But for now I will leave it around and open.

Comment 2

[Jeff Walden [:Waldo]]

This got fixed at some point during UTF-8 script work, as there's a JS::Compile entrypoint accepting UTF-8, and no entrypoints inflate any more.