problematic assignment operation added by wrapReadWithUndefinedCheck

[JacksonGL]

A website does not work after transformation. And it turns out that it is because wrapReadWithUndefinedCheck function adds variable = variable operation during transformation. For example, the following statement:

postArgMessage; will be transformed into:

J$.I(typeof postArgMessage === 'undefined' ? postArgMessage = J$.R(5, 'postArgMessage', undefined, true) : postArgMessage = J$.R(5, 'postArgMessage', postArgMessage, true)

which assigns the return value (its own value, if the analysis code does not modify that) to the variable. That can be problematic sometime, for example, execute:

location = location;

in the frontend means reloading the webpage. (This bug has been fixed).
But There are still other special global objects that should not be assigned to itself. For example, in HTML5 webworker (fontend multithreading environment), execute:

self = self;

will cause 'setting a property that has only a getter' exception.

Maybe this is not a serious bug as webworker is not supposed to be supported by Jalangi. But there might be other special objects that can trigger errors if they are assigned to themselves. That might potentially cause more bugs which are hard to diagnose.

JacksonGL