CERT C: Rec. DCL05-C

Use typedefs of non-pointer types only

Since R2026a

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Description

Use typedefs of non-pointer types only1

Polyspace Implementation

The rule checker checks for Use of typedef of pointer types.

Examples

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Issue

This issue occurs when the code defines a typedef of a pointer type that points to a non-const and non-volatile type and then uses the typedef with a const or volatile qualifier. For example:

typedef int* intptr;
const intptr p2i; //Noncompliant

Risk

If you apply const or volatile qualifier to a typedef of a pointer type, the qualifier is applied to the pointer type, not the underlying object to which the pointer points. For example, in this code, p2i is a const pointer to a non-const integer. It is possible to modify the underlying object, which can be unexpected.

void foo(const intptr p2i){
    *(p2i)++; //Modify the content to p2i
    // ++p2i; Fails compilation  
}
Using typedef for pointer types can result in code that is not const-correct.

Fix

To fix this issue:

  • Define typedefs for base nonpointer types.

  • For typedefs of pointer types, include the const-correct definition of the type in the typedef statement.

Example

In this code, Polyspace® reports violation on the use of const-qualifier on the typedef of a pointer type.

typedef struct {
    int x;
    int y;
} *PointPtr;

float getDistance(const PointPtr firstPoint, const PointPtr secondPoint){ //Noncompliant 
    //
}

Correction

To fix this issue, change the typedef definition. You can take either of these steps:

  • Change the typedef to a nonpointer type and then use a pointer of the typedef with appropriate const-ness. This is demonstrated by the function getDistance().

  • Include the appropriate const qualifier directly in the typedef. This is demonstrated by the function alternateGetDistance().

typedef struct {
    int x;
    int y;
} Point;

float getDistance(const Point *firstPoint, const Point *secondPoint){ //Compliant
    //
}


typedef const struct {
    int x;
    int y;
} *Ptr2ConstPoint;


float alternateGetDistance(Ptr2ConstPoint firstPoint, Ptr2ConstPoint SecondPoint){ //Compliant
    //...
}

Check Information

Group: Rec. 02. Declarations and Initialization (DCL)
PQL Name: std.cert.DCL05_C

Version History

Introduced in R2026a

See Also

Topics

External Websites

1 This software has been created by MathWorks incorporating portions of: the “SEI CERT-C Website,” © 2017 Carnegie Mellon University, the SEI CERT-C++ Web site © 2017 Carnegie Mellon University, ”SEI CERT C Coding Standard – Rules for Developing safe, Reliable and Secure systems – 2016 Edition,” © 2016 Carnegie Mellon University, and “SEI CERT C++ Coding Standard – Rules for Developing safe, Reliable and Secure systems in C++ – 2016 Edition” © 2016 Carnegie Mellon University, with special permission from its Software Engineering Institute.

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