Vala property getters and setters default to public linkage

Default Accessor Behavior in Vala

In Vala, automatically generated property getters and setters inherit the accessibility modifier of the property declaration itself. If no modifier is specified, the property defaults to public, and consequently, both the getter and setter are generated as public methods in the resulting C code.

Analysis of Default Linkage Changes

The Risk of ABI Breakage

Changing the default accessibility of accessors (e.g., from public to private) would result in a breaking change to the Application Binary Interface (ABI). Because Vala maps properties to specific C functions, altering the visibility of these functions would prevent existing compiled binaries from linking correctly against updated libraries. This would necessitate a major version bump of the language and its core libraries.

Proposed Migration Strategies

To mitigate ABI breakage while improving encapsulation, the following strategies are typically considered:

• Opt-in Flags: Introduce a compiler flag (e.g., --private-properties) that allows developers to toggle the new behavior on a per-project basis.
• Explicit Modifier Requirement: Transition toward a requirement where properties must have an explicit modifier, issuing a deprecation warning for those relying on the default.
• Phased Deprecation: Maintain the public default in the current stable release while implementing the restrictive default in a new major version (e.g., Vala 0.x to 1.0).

Current Enforcement of Private Access

Developers can currently prevent public exposure of internal state using these methods:

Explicit Property Modifiers

The most direct way to ensure private accessors is to mark the property as private. This ensures that neither the property nor its generated accessors are visible outside the class.

private int internal_state;

Custom Accessors

To allow public reading but private writing, developers can define a public property with a private setter:

public int state { get; private set; }

Verification

To verify the current linkage of a property, compile a Vala file and inspect the generated C source. A public property will generate C functions without restrictive visibility markers, making them accessible to any object that can see the class instance.

Diagnostic Detail: Are you targeting a specific GObject-based API where the GParamSpec must remain public for introspection, even if the method accessors are private?