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Typically, the amount of memory to allocate will be the size of the type of object to allocate. When allocating space for an array, the size of the object will be multiplied by the bounds of the array. When allocating space for a structure containing a flexible array member, the size of the array member must be added to the size of the structure. (see See MEM33-C. Allocate and copy structures containing a flexible array member dynamically.) . Use the correct type of the object when computing the size of memory to allocate.

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In this noncompliant code example, an array of long is allocated and assigned to p. The code checks for unsigned integer overflow in compliance with INT32-C. Ensure that operations on signed integers do not result in overflow and also ensures that len is not equal to zero. (see See MEM04-C. Beware of zero-length allocations.) . However, because sizeof(int) is used to compute the size, and not sizeof(long), an insufficient amount of memory can be allocated on implementations where sizeof(long) is larger than sizeof(int) .

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Tool

Version

Checker

Description

CodeSonar

Include Page

	CodeSonar_V
	CodeSonar_V

ALLOC.SIZE.ADDOFLOW
ALLOC.SIZE.IOFLOW
ALLOC.SIZE.MULOFLOW
ALLOC.SIZE.SUBUFLOW
ALLOC.SIZE.TRUNC
IO.TAINT.SIZE
MISC.MEM.SIZE.BAD

Addition overflow of allocation size
Addition overflow of allocation size
Multiplication overflow of allocation size
Subtraction underflow of allocation size
Truncation of allocation size
Tainted allocation size
Unreasonable size argument

Compass/ROSE

Could check violations of this rule by examining the size expression to malloc() or memcpy() functions. Specifically, the size argument should be bounded by 0, SIZE_MAX, and, unless it is a variable of type size_t or rsize_t, it should be bounds-checked before the malloc() call. If the argument is of the expression a*b, then an appropriate check is

Code Block
if (a < SIZE_MAX / b && a > 0) ...

Coverity

Include Page

	Coverity_V
	Coverity_V

BAD_ALLOC_STRLEN

SIZECHECK

Can find instances where string length is miscalculated (length calculated may be one less than intended) for memory allocation purposes. Coverity Prevent cannot discover all violations of this rule, so further verification is necessary

Finds memory allocations that are assigned to a pointer that reference objects larger than the allocated block

Fortify SCA

5.0

Can detect violations of this rule with CERT C Rule Pack, except those involving the sizeof operator

Klocwork

9.1

INCORRECT.ALLOC_SIZE

LDRA tool suite

Include Page