[webkit-dev] Bytecode Sequence for function.apply()

Nyx mcheva at cs.mcgill.ca
Thu May 20 08:42:28 PDT 2010

I've been working on a tool to generate a trace of JavaScript executions,
built on JavaScriptCore. I'm trying to log calls to all functions and their
arguments. To do this, I've instrumented the op_call and op_call_varargs
bytecodes in Interpreter.cpp.

The problem I'm having is that if someone calls a native/host function
through apply, I don't see the call. For example, the call:

string.fromCharCode.apply(null, [65, 66, 67]);

Doesn't seem to correspond to an op_call or op_call_varargs, so I'm
wondering how this is handled in JavaScriptCore, what kind of bytecodes
generated, and if somebody has any idea what I could do to log the "unseen"
calls to native functions, short of instrumenting every native function in
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