bug#13074: VM Segfaults with Bad `Call' Instruction

[Noah Lavine]

On Tue, Dec 11, 2012 at 4:42 AM, Ludovic Courtès <address@hidden> wrote:

The VM does full error checking.  But there’s a difference between
checking whether an object has the expected type, and checking whether
an object is a well-formed ‘SCM’ object (and NULL is not a valid ‘SCM’
object.)

Guile never does the latter, and as a rule of thumb I would keep things
this way.

Okay.

 

The brave hacker working on a compiler can easily figure out what how to
debug all sorts of crazy things.  :-)

Yes, "easily". :-)

 

So I’m closing it for now.

Thanks,
Ludo’.

PS: It’s still unclear to me how you ended up forging an invalid SCM
    object.  I think you either have to generate invalid bytecode, or to
    use (pointer->scm %null-pointer), or variants thereof.

I loaded a procedure on the stack, used the new-frame instruction, and then the call instruction. When I switched the order of the first two things, the problem went away. I must have been using uninitialized stack space.

Noah