On Friday, 19 February 2016 at 22:34:48 UTC, Chris Wright wrote:
I tested this a fair bit today, and I haven't been able to do
any of the nefarious things I expected to be able to do. No
overwriting variables in the caller's scope, no smashing stack
pointers, etc.
I was surprised by this result, but in retrospect, it's
relatively obvious. The caller pushes variables onto the stack
and sets the stack pointer for the callee. It wouldn't send a
stack pointer that pointed into its own stack frame.
Thanks for taking the time to test.
The more I've thought about it, the more I wonder if there should
be a restriction so that casts of function pointers/delegate
maintain the same number of parameters. Even though you haven't
been able to do nefarious things, it's giving a completely wrong
answer than you would expect. The result of the answer might
cause bad things to happen in a program. Further, to even
understand what's going wrong you have to understand how the
compiler is generating assembly. I've been using D for like a
year or so, and I would never have been able to figure out the
reason by myself.
Or at least in safe code you shouldn't be able to do this.
