PRE03-C. Prefer typedefs to defines for encoding non-pointer types

Prefer type definitions (typedef) to macro definitions (#define) when encoding types. Type definitions obey scope rules; macro definitions do not. textual substitution is inferior to using the type system. While type definitions for non-pointer types have similar advantages [Summit 2005], can make it more difficult to write const-correct code (see DCL05-C. Use typedefs of non-pointer types only).

Noncompliant Code Example

This noncompliant example will not compile, because macros use textual substitution and not the type system:  [also doesn't work with a single variable per line]

#define MATRIX double matrix[4][4]
MATRIX matrix_a, matrix_b;

Compliant Solution

This compliant solution compiles correctly.

typedef double matrix[4][4]; 
matrix matrix_a, matrix_b;

This code example also violates DCL04-C. Do not declare more than one variable per declaration. [is doing so necessary or useful for the example]

Noncompliant Code Example

I don't actually know what is wrong with this:

#define uchar unsigned char

Compliant Solution

Use type definitions to encode all non-pointer types.

typedef unsigned char uchar;

Risk Assessment

Automated Detection

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Bibliography