Module Search Paths

This document describes how modules are located by the current implementation of Chapel.

Internal modules are always loaded by a chapel program as if the statement use ChapelStandard; has been inserted ahead of the first statement in the main module. Unlike standard modules, internal modules cannot be overridden.

The compiler uses three module search paths: one for internal modules, one for standard and package modules, and one for user modules. The user path first includes all the paths used to specify module files directly on the chpl command line and then includes the paths specified via -M commands or through the CHPL_MODULE_PATH environment variable.

The module search paths are initialized as follows:

  • Internal
    • various directories under $CHPL_HOME/modules/internal

  • Standard

    • $CHPL_HOME/modules/standard

    • $CHPL_HOME/modules/packages

    • $CHPL_HOME/modules/layouts

    • $CHPL_HOME/modules/dists

    • $CHPL_HOME/modules/dists/dims

  • User

    • (User paths)

When the root internal module ChapelStandard and its dependencies are loaded, the internal module path is searched first. If a module is found there, it is marked as internal. Otherwise, it is skipped.

The user’s modules are parsed next. If a module named in a use statement is not found, the standard version is loaded instead if it exists. Otherwise, a file-not-found error will be issued. If both user and standard versions of a module exists, the user is warned that the standard version is being overridden.