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 code example will not compile, because macros use textual substitution and not the type system: 

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

After preprocessing, this code example is translated to the following invalid declaration:

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

Compliant Solution

Using type definitions instead of macro definitions in this compliant solution results in a valid declaration:

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

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