Re: C++ -> Java VM compiler

I was looking at the JVM spec with the idea of doing a C compiler.


Presumably through gcc, so maybe similar questions.


Pointer arithmetic is a little tricky, but not that bad. The problem
is that you can't cast pointers and dereference them as a different
type. You can't have a malloc() that returns (char*) and use it as an
(int*). However, if you have malloc_int(), malloc_double(), etc, it
should work. This means a little rewriting of code, but much less
than rewriting in Java.


There is only one kind of pointer variable, but pointers remember what
they point to. An (int*) can be assigned to (char*) and back to (int*)
and used.


Note also that the (int*) type really has to be something like


struct intpointer {
int *origin;
int offset;
};


As there is no way to add to a pointer. The add and dereference are
one operation. But if the pointer type includes the offset, then all
arithmetic can be done on that, and then it is used at dereference.


varargs functions might be complicated in a similar way, but there
may be ways around this, also.


I would be interested to hear from anyone else with any thoughts
about this problem.


-- glen
--

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