PRE03-C. Prefer typedefs to defines for encoding types

Prefer type definitions (typedef) to macro definitions (#define) when encoding types. Type definitions obey scope rules; macro definitions do not. Type definitions can also correctly encode pointer types because they are not implemented as simple textual substitution. In the following declaration, the variable p is declared as a constant pointer to char [Summit 2005]:

typedef char *NTCS;
const NTCS p = &data;

Noncompliant Code Example

In this noncompliant code example, s1 is declared as char *, but s2 is declared as a char, which is probably not what the programmer intended:

#define cstring char *
cstring s1, s2;

This noncompliant code example also violates DCL04-C. Do not declare more than one variable per declaration.

Compliant Solution

In this compliant solution, both s1 and s2 are declared as char *:

typedef char * cstring;
cstring s1;
cstring s2;

The compliant solution violates DCL05-C. Use typedefs of non-pointer types only, but effectively demonstrates the difference between type definitions and macro replacements.

Risk Assessment

Automated Detection

Related Vulnerabilities

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

Related Guidelines

Bibliography