On Thursday, 20 April 2017 at 02:27:37 UTC, Nick Sabalausky
(Abscissa) wrote:
According to <http://dlang.org/phobos/core_memory.html>:
"Registers, the stack, and any other memory locations added
through the GC.addRange function are always scanned
conservatively."
1. Can that be safely assumed to be a canonical list of all
possible sources of false pointers?
2. What about memory allocated through language constructs such
as "new", append ("~"/"~="), closures, or any others I may be
forgetting? Is this memory always/never/sometimes set to
NO_SCAN? (I assume not "always", as that would be silly.) If
"sometimes", what are the conditions?
A couple specific examples:
3. Are there any situations where a (for example) int[] or
long[] that is stored on the GC heap could lead to false
pointers?
4. Same question as #3, but if it's an array of structs, and
the struct type contains no members that are statically-typed
as pointers.
1. No, that's not the full list. Closures are indeed an important
source of GC-allocated objects with pointers and often false
pointers, for example.
2. With "new" compiler decides by the type whether the data may
contain pointers, so arrays of numbers or arrays of structs with
no pointers inside will be allocated as NO_SCAN.
3-4. As long as the compiler is sure about absence of pointers in
allocated type, you're safe, I don't see a way for that data to
become a source of false pointers (unless you fool the compiler
with casts).
