14.1.5 Complexity Metrics Control

For a program unit that is an executable body (a subprogram body (including generic bodies), task body, entry body or a package body containing its own statement sequence ) gnatmetric computes the following complexity metrics:

• McCabe cyclomatic complexity;
• McCabe essential complexity;
• maximal loop nesting level

The McCabe complexity metrics are defined in www.mccabe.com/pdf/nist235r.pdf

According to McCabe, both control statements and short-circuit control forms should be taken into account when computing cyclomatic complexity. For each body, we compute three metric values:

• the complexity introduced by control statements only, without taking into account short-circuit forms,
• the complexity introduced by short-circuit control forms only, and
• the total cyclomatic complexity, which is the sum of these two values.

When computing cyclomatic and essential complexity, gnatmetric skips the code in the exception handlers and in all the nested program units.

By default, all the complexity metrics are computed and reported. For more finely-grained control you can use the following switches:

-nocc

Do not compute the McCabe Cyclomatic Complexity

-noec

Do not compute the Essential Complexity

-nonl

Do not compute maximal loop nesting level

-ne

Do not consider exit statements as gotos when computing Essential Complexity