LANG.STRUCT.SUP : Subtraction of Unrelated Pointers

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Pointer subtraction is performed between pointers to different objects.

Pointer subtraction should only be performed between pointers that point at different elements of the same array. Subtracting pointers that point at different variables or allocations is undefined behavior according to the C and C++ standards.

Class Name

Subtraction of Unrelated Pointers

Significance

reliability

Mnemonic

LANG.STRUCT.SUP

Categories

MisraC2023	MisraC2023:18.2	Subtraction between pointers shall only be applied to pointers that address elements of the same array
Misra2012	Misra2012:18.2	Subtraction between pointers shall only be applied to pointers that address elements of the same array
Misra2004	Misra2004:17.2	Pointer subtraction shall only be applied to pointers that address elements of the same array
	Misra2004:17.4	Array indexing shall be the only allowed form of pointer arithmetic
AUTOSARC++14	AUTOSARC++14:M5-0-15	Array indexing shall be the only form of pointer arithmetic.
	AUTOSARC++14:M5-0-17	Subtraction between pointers shall only be applied to pointers that address elements of the same array.
MisraC++2008	MisraC++2008:5-0-15	Array indexing shall be the only form of pointer arithmetic.
	MisraC++2008:5-0-17	Subtraction between pointers shall only be applied to pointers that address elements of the same array.
MisraC++2023	MisraC++2023:8.7.2	Subtraction between pointers shall only be applied to pointers that address elements of the same array
CWE	CWE:469	Use of Pointer Subtraction to Determine Size
TS17961	TS17961:5.35-ptrobj	5.35. Subtracting or comparing two pointers that do not refer to the same array
CERT-C	CERT-C:ARR36-C	Do not subtract or compare two pointers that do not refer to the same array
	CERT-C:EXP08-C	Ensure pointer arithmetic is used correctly
CERT-CPP	CERT-CPP:CTR54-CPP	Do not subtract iterators that do not refer to the same container

Availability

Available for C and C++.

Enabling

Checks for this warning class are enabled by default. To disable them, add the following WARNING_FILTER rule to the project configuration file.

WARNING_FILTER += discard class="Subtraction of Unrelated Pointers"

int f()
{
    int i, j;
    return (int)(&i - &j); /* 'Subtraction of Unrelated Pointers' warning issued here */
}

The following configuration file parameters affect checks for this warning class.

LANG.STRUCT.SUP : Subtraction of Unrelated Pointers

Summary

Properties

Example

Relevant Configuration File Parameters