finalization after dependency

Finalization reaching a unit already finalized (finalization-after-dependency)

A finalization section reaches a global variable of a unit that has already been finalized, and that unit's finalization is what tears the variable down. The read sees a freed object, usually as an access violation on exit. ON by default in lint-all and lint-project.

Running it

drag-lint lint-all --db <project.sqlite> --rule finalization-after-dependency
drag-lint lint-project --db <project.sqlite> --rule finalization-after-dependency

It needs an index that holds the .dpr, and an index that has resolved references to sections (1.44 or later).

The order

Finalization runs in the reverse of initialization, so a unit that initializes later is finalized earlier. The initialization order is computed from the uses clauses as described in init-order-hazard. A unit that uses another without a cycle is always finalized before it, so this rule can only fire inside a uses cycle.

What it reports

One warning per section's unit, earlier unit and variable, at the call or reference in the section that starts the path. A variable counts as torn down when the earlier unit's finalization, or a routine of that unit the section calls, names it.

What stays silent

• A routine that also assigns the variable, or tests it against nil or with Assigned. That covers the FreeAndNil plus Assigned idiom.
• A local, parameter or class member of the same name.
• A variable the earlier unit's finalization does not name.
• A call through virtual dispatch or a callback, and a call the index resolved only as ambiguous.
• A package: only a .dpr gives an order here.