A5-0-3 - Unofficial Autosar C++ Guidelines Reference

Rule A5-0-3 (required, implementation, automated)

The declaration of objects shall contain no more than two levels of pointer indirection.

Rationale

Use of more than two levels of indirection can seriously impair the ability to understand the behavior of the code, and therefore should be avoided.

Example

// $Id: A5-0-3.cpp 289436 2017-10-04 10:45:23Z michal.szczepankiewicz $
#include <cstdint>

using IntPtr = std::int8_t*;

struct S
{

std::int8_t* s1;

std::int8_t** s2;

// Compliant
// Compliant

std::int8_t*** s3;

// Non-compliant

};

S* ps1;

// Compliant

S** ps2;

// Compliant

S*** ps3; // Non-compliant

std::int8_t**

(*pfunc1)();

// Compliant

std::int8_t**

(**pfunc2)();

// Compliant

std::int8_t** (***pfunc3)(); // Non-compliant

std::int8_t*** (**pfunc4)(); // Non-compliant

void Fn(std::int8_t* par1,
std::int8_t** par2,

// Compliant
// Compliant

Guidelines for the use of the C++14 language in
critical and safety-related systems

std::int8_t*** par3,

// Non-compliant

IntPtr* par4,

IntPtr* const* const par5,

std::int8_t* par6[],

// Compliant
// Non-compliant
// Compliant

std::int8_t** par7[])

// Non-compliant

{

std::int8_t* ptr1;

std::int8_t** ptr2;

std::int8_t*** ptr3;

IntPtr* ptr4;

IntPtr* const* const ptr5 = nullptr;

std::int8_t* ptr6[10];

// Compliant
// Compliant
// Non-compliant
// Compliant
// Non-compliant
// Compliant

std::int8_t** ptr7[10];

// Compliant

}

// Explanation of types
// 1) par1 and ptr1 are of type pointer to std::int8_t.
// 2) par2 and ptr2 are of type pointer to pointer to std::int8_t.
// 3) par3 and ptr3 are of type pointer to a pointer to a pointer
// to std::int8_t.
// This is three levels and is non-compliant.
// 4) par4 and ptr4 are expanded to a type of pointer to a pointer to
// std::int8_t.
// 5) par5 and ptr5 are expanded to a type of const pointer to a const
// pointer
// to a pointer to std::int8_t. This is three levels and is non-compliant.
// 6) par6 is of type pointer to pointer to std::int8_t because arrays
// are converted
// to a pointer to the initial element of the array.
// 7) ptr6 is of type pointer to array of std::int8_t.
// 8) par7 is of type pointer to pointer to pointer to
// std::int8_t because arrays are
// converted to a pointer to the initial element of the array. This is
// three
// levels and is non-compliant.
// 9) ptr7 is of type array of pointer to pointer to std::int8_t. This
// is compliant.

Unofficial Autosar C++ Guidelines Reference

Rationale

Example

See also