14.10 Code Inspectors

In the same way that inspectors control access to structure fields (see Structure Inspectors), inspectors also control access to module bindings. Inspectors used this way are code inspectors. The default code inspector for module bindings is determined by the current-code-inspector parameter, instead of the current-inspector parameter.

When a module declaration is evaluated, the value of the current-code-inspector parameter is associated with the module declaration. When the module is invoked via require or dynamic-require, a sub-inspector of the module’s declaration-time inspector is created, and this sub-inspector is associated with the module invocation. Any inspector that controls the sub-inspector (including the declaration-time inspector and its superior) controls the module invocation. In particular, if the value of current-code-inspector never changes, then no control is lost for any module invocation, since the module’s invocation is associated with a sub-inspector of current-code-inspector.

When an inspector that controls a module invocation is installed with current-code-inspector, it enables using module->namespace on the module, and it enables access to the module’s protected exports (i.e., those identifiers exported from the module with protect-out) via dynamic-require. A module cannot require a module that has a weaker declaration-time code inspector.

When a module form is expanded or a namespace is created, the value of current-code-inspector is associated with the module or namespace’s top-level lexical information. Syntax objects with that lexical information gain access to the protected and unexported bindings of any module that the inspector controls. In the case of a module, the inspector sticks with such syntax objects even the syntax object is used in the expansion of code in a less powerful context; furthermore, if the syntax object is an identifier that is compiled as a variable reference, the inspector sticks with the variable reference even if it appears in a module form that is evaluated (i.e., declared) with a weaker inspector. When a syntax object or variable reference is within compiled code that is printed (see Printing Compiled Code), the associated inspector is not preserved.

When compiled code in printed form is read back in, no inspectors are associated with the code. When the code is evaluated, the instantiated syntax-object literals and module-variable references acquire value of current-code-inspector as their inspector.

When a module instantiation is attached to multiple namespaces, each with its own module registry, the inspector for the module invocation can be registry-specific. The invocation inspector in a particular module registry can be changed via namespace-unprotect-module (but changing the inspector requires control over the old one).

Changed in version 8.1.0.8 of package base: Added constraint against require of a module with a weaker code inspector.

If the code inspector is changed from its original value, then bytecode loaded by the default compiled-load handler is marked as non-runnable.