Page History

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:  [also doesn't work with a single variable per line]

#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_b[4][4]
double matrix[4][4] matrix_a;

Compliant Solution

This compliant solution compiles correctly.Using type definitions instead of macro definitions in this compliant solution results in a valid declaration:

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

...

Noncompliant Code Example

...

#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

...

...

Image Modified Image Modified Image Modified