Re: [cs] Robustify in the presence of PCH n snarf-n-barf

[Mike Stump <mrs at apple dot com>]

On Thursday, October 30, 2003, at 01:14 PM, Geoff Keating wrote:
> This change is wrong, please make sure it never gets into mainline GCC.

Please explain how one can have two pointers to the same piece of GCed 
data that have different static types on them?

In C++, this would be:

class Base {
} *base;

class Derived : public base {
} *derived;

int main() {
	base = derived = new Derived;
}

In C, this would be:

tree base;
tree_decl derived;

int main() {
	base = derived = make_decl ();
	return 0;
}

Per and I are experimenting with tightening up the compiler to include 
more static typing, so that we can have the compiler's static type 
system diagnose type errors instead of depending upon DECL_CHECK as 
much.  This aids readability, give type violations sooner, and has 
other good benefits.

The C++ runtime system has the exact same code as your PCH code, but, 
it does all the required runtime conversions, unlike your code.  Please 
explain why your code isn't just plain wrong.