# `dead_code_scanner`

This tool detects likely dead code in Logtalk entities and in Prolog modules compiled as objects. Predicates (and non-terminals) are classified as dead code when:

1. There is no scope directive for them.

2. They are not called, directly or indirectly, by any predicate with a (local or inherited) scope directive.

Predicates (and non-terminals) listed in `uses/2` and `use_module/2` directives but that are not used are also classified as dead code.

Besides dead code, this tool can also help detect other problems in the code that often result in reporting false positives. For example, typos in `alias/2` directives, missing scope directives, and missing `meta_non_terminal/1` and `meta_predicate/1` directives.

Given the possibility of false positives, care must be taken before deleting reported dead code to ensure that it’s, in fact, code that is not used. A common cause of false positives is the use of conditional compilation directives to provide implementations for predicates missing in some systems.

The `dead_code_scanner.lgt` source file implements the scanning predicates for finding dead code in entities, libraries, and directories. The source file `dead_code_scanner_messages.lgt` defines the default translations for the messages printed when scanning for dead code. These messages can be intercepted to customize output, e.g. to make it less verbose, or for integration with e.g. GUI IDEs and continuous integration servers.

## API documentation

To consult this tool API documentation, open in a web browser the link:

docs/library_index.html#dead-code-scanner

For sample queries, please see the SCRIPT.txt file in the tool directory.

## Loading

This tool can be loaded using the query:

    | ?- logtalk_load(dead_code_scanner(loader)).

## Known issues

Use of local meta-calls with goal arguments only known at runtime can result in false positives. When using library or user-defined meta-predicates, it can be helpful to compile the source files with the `optimize` flag turned on so that the meta-calls may be resolved at compile time and thus allow calling information for the meta-arguments to be recorded, avoiding false positives for predicates that are only meta-called.

## Other notes

All source files are indented using tabs (a common setting is a tab width equivalent to 4 spaces).