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# 9. The generic fix function

# 10. Introduction

Fix is the interface through which the existence of references are communicated from the MPS client to the MPS. The interface also allows the value of such references to be changed (this is necessary in order to implement a moving memory manager).

# 11. History

.hist.0: Incomplete design. Richard Brooksby, 1995-08-25.

.hist.1: Converted from MMInfo database design document. Richard Brooksby, 2002-06-07.

.hist.2: Converted to reStructuredText. Gareth Rees, 2013-04-14.

# 12. Architecture

.protocol.was-marked: The `ScanState` has a `Bool` `wasMarked` field. This is used for finalization.

.protocol.was-marked.set: All pool-specific fix methods must set the `wasMarked` field in the `ScanState` that they are passed.

.protocol.was-marked.meaning: If the pool-specific fix method sets the `wasMarked` field to `FALSE` it is indicating the object referred to by the ref (the one that it is supposed to be fixing) has not previously been marked (ie, this is the first reference to this object that has been fixed), and that the object was white (in condemned space).

.protocol.was-marked.conservative: It is always okay to set the `wasMarked` field to `TRUE`.

.protocol.was-marked.finalizable: The MRG pool (design.mps.poolmrg) uses the value of the `wasMarked` field to determine whether an object is finalizable.

# 13. Implementation

.fix.nailed: In a copying collection, a non-ambiguous fix to a broken heart should be snapped out even if there is a `RankAMBIG` ref to same object (that is, if the broken heart is nailed); the `RankAMBIG` reference must either be stale (no longer in existence) or bogus.

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