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Invalid assumptions about memory organization

Address is computed by adding or subtracting from address of a variable

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Description

This defect occurs when you compute the address of a variable in the stack by adding or subtracting from the address of another non-array variable.

Risk

When you compute the address of a variable in the stack by adding or subtracting from the address of another variable, you assume a certain memory organization. If your assumption is incorrect, accessing the computed address can be invalid.

Fix

Do not perform an access that relies on assumptions about memory organization.

Examples

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void func(void) {
    int var1 = 0x00000011, var2;
    *(&var1 + 1) = 0;
}

In this example, the programmer relies on the assumption that &var1 + 1 provides the address of var2. Therefore, an Invalid assumptions about memory organization appears on the + operation. In addition, a Pointer access out of bounds error also appears on the dereference.

Correction — Do Not Rely on Memory Organization

One possible correction is not perform direct computation on addresses to access separately declared variables.

Result Information

Group: Programming
Language: C | C++
Default: On for handwritten code, off for generated code
Command-Line Syntax: INVALID_MEMORY_ASSUMPTION
Impact: Medium

Version History

Introduced in R2015b

See Also

Topics