1137980 - enable JSJitInfo ops to be type-checked harder by the compiler

Status: NEW

(Core :: JavaScript Engine: JIT, enhancement, P5)

Description

[Nathan Froyd [:froydnj]]

Currently in the bindings code, we have things like:

static const JSJitInfo x_getterinfo = {
 { (JSJitGetterOp)get_x },
 ...

No matter what kind of thing this is jit info for, we cast the op to JSJitGetterOp, which handily defeats any type-checking the compiler might do for us.  Folks adding things to bindings can sometimes get bit very hard by this.

It's been a while since I looked at this, but I think the reason was that you have to initialize unions with the type of their first member.  But that was partly because we were on old MSVC, and I think C++11 was supposed to improve the situation somewhat in this department.

If C++11 hasn't improved things markedly, or the solution requires static constructors for every JSJitInfo, we should invent some gnarly type-checking macros + templates and use those instead.

Comment 1

[Boris Zbarsky [:bzbarsky]]

C++11 added nicer initialization for all sorts of stuff... but afaict not unions.  :(