DCL05-C. Use typedefs to improve code readability

Use type definitions (typedef) to improve code readability.

Noncompliant Code Example

The following declaration of the signal() function is difficult to read and comprehend.

void (*signal(int, void (*)(int)))(int);

Compliant Solution

This compliant solution makes use of type definitions to specify the same type as in the noncompliant code example.

typedef void (*SighandlerType)(int signum);
extern SighandlerType signal(
  int signum, 
  SighandlerType handler
);

Risk Assessment

Code readability is important for discovering and eliminating vulnerabilities.

Automated Detection

The LDRA tool suite V 7.6.0 can detect violations of this recommendation.

Compass/ROSE could detect violations of this recommendation...typedefs are well represented in ROSE's AST. To detect violations, we first have to rigorously define what constitutes a 'too complicated type'. Most could concede that a pointer to a simple type is not too complicated, but a function type is. The algorithm we will employ to flag declarations that warrant a typedef is as follows:

• Any pointer is worth 1 point
• Any function type is worth 2 points (1 for the function and 1 for the customary pointer to function)
• Any variable declaration with 5 or more points warrants a typedef.

Related Vulnerabilities

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

References

[[ISO/IEC 9899:1999]] Section 6.7.7, "Type definitions"
[[ISO/IEC PDTR 24772]] "BRS Leveraging human experience"

      02. Declarations and Initialization (DCL)       DCL06-C. Use meaningful symbolic constants to represent literal values in program logic