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Issue
792163003:
Deletion barrier preparation: validate overwritten references. (Closed)
DescriptionDeletion barrier preparation: validate overwritten references.
With the upcoming deletion barrier, every update of a pointer field must know whether the previous value was a valid pointer.
Currently, we always use StorePointer/StoreSmi, both for initialization and updates.
Initialization, and thus the potential for overwriting garbage values, appears in three places:
1. Object::Allocate/Foo::New.
2. Creating isolate from full snapshot.
3. Allocation in generated code.
Case 1 already null-initializes all underlying memory.
Case 2 is addressed by this CL by exploiting that:
i) fresh pages are zero-filled by OS, and
ii) freelist headers use only even values.
Case 3 is remains a TODO for future CLs.
(An alternative solution for case 2 would have been to add an init_foo method for every set_foo called.)
R=iposva@google.com
Committed: https://code.google.com/p/dart/source/detail?r=42584
Patch Set 1 #Patch Set 2 : #Patch Set 3 : #Patch Set 4 : #Patch Set 5 : #
Total comments: 4
Patch Set 6 : #Patch Set 7 : #
Messages
Total messages: 5 (0 generated)
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