Detect typedef of typedefs

This example shows how to use Polyspace Query Language (PQL) to check for violation of this rule: Do Not define typedef of typedefs.

This topic focuses on application of PQL. For more details about creating semantic defect checkers, see Detect Semantic Issues Using Polyspace Query Language Semantic Classes.

Analyze Rule

To implement the rule in PQL, analyze the components of the rule:

  • Type of a variable — Use the class Type to identify variable types.

  • Checking for typedefs of typedefs — Find typedef types, and then check if their underlying types are typedefs themselves.

Implement Rule in PQL

The defect can be defined like this:

defect recursiveTypedef =
			when
                Cpp.TYpe.is(&type) and
                type.isTypedef() and // Check if type is a type def
                type.underlyingType(&base_type) and 
                base_type.isTypedef() // check if the underlying type of a typedef is also a typedef
                raise "Recursive typedef is forbidden. {base_type} is already a typedef."
			on var

Test Defect

To test and verify the defect:

  1. Initialize a test standard in a writable location:

    polyspace-query-language init

  2. In main.pql, insert the defect in a test standard:

    package main

// Main PQL file defines the catalog of your PQL project.
// The catalog is a collection of sections.
catalog PQL_Expression_example = {
#[Description("MySection")]
	section mysection = {
#[Description("myRule"), Id(Rule1)]
		rule myRule = {
			defect recursiveTypedef =
			when
                Cpp.Variable.is(&var) and
                var.type(&type) and
                type.isTypedef() and
                type.underlyingType(&base_type) and
                base_type.isTypedef()
                raise "Recursive typedef is not allowed. {base_type} is already a typedef."
			on var
		}
	}
}

  3. Package the standard in a pschk file:

    polyspace-query-language package

  4. Create example.cpp in the same folder:

    /* Do Not define typedef of typedefs. */
typedef struct _SomeStruct {
        unsigned char fu1_someFlag;
} SomeStruct;

typedef SomeStruct someTypedefedType;
someTypedefedType gst_command_type2; //  expect-1-Rule1
    This code explicitly states where a violation of the rule is expected using annotation expect-1-Rule1. Absence of the violation is also annotated using expect-0-Rule1.

  5. Run a test for the defect on the example code:

    polyspace-query-language test example.cpp
    The test verifies the expected violations as well as the expected absence of violations:
    Number of actual defects: 1
Number of expected annotations: 1 (including 0 expected absence of defects).
_______________________________________________
  Checking expected defects with actuals...
  -----------------------------------------
_______________________________________________
  Looking for unexpected defects...
-------------------------------------------
_______________________________________________
Tests passed

See Also

Topics