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The C99 standard \[[ISO/IEC 9899:1999\|AA. References#ISO/IEC 9899-1999]\] identifies four distinct situations in which undefined behavior (UB) may arise as a result of invalid pointer operations:

UB	Description	Example Code
43	Addition or subtraction of a pointer into, or just beyond, an array object and an integer type produces a result that does not point into, or just beyond, the same array object.	#Forming Out Of Bounds Pointer
44	Addition or subtraction of a pointer into, or just beyond, an array object and an integer type produces a result that points just beyond the array object and is used as the operand of a unary `*` operator that is evaluated.	#Dereferncing Out Of Bounds Pointer
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="cece2b2c135992fe-f2572f49-4c724fc6-b09799f1-b994b9c3f67e24ea49436a49"><ac:plain-text-body><![CDATA[	[46	CC. Undefined Behavior#ub_46]	An array subscript is out of range, even if an object is apparently accessible with the given subscript (as in the lvalue expression `a[1][7]` given the declaration `int a[4][5]`).	[#Apparently Accessible Out Of Range Index]	]]></ac:plain-text-body></ac:structured-macro>
59	An attempt is made to access, or generate a pointer to just past, a flexible array member of a structure when the referenced object provides no elements for that array.	#Pointer Past Flexible Array Member

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	Forming Out Of Bounds Pointer
	Forming Out Of Bounds Pointer

Noncompliant Code Example (Forming Out Of Bounds Pointer)

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Code Block

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enum { TABLESIZE = 100 };

static int table[TABLESIZE];

int* f(size_t index) {
  if (index < TABLESIZE)
    return table + index;

  return NULL;
}

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	Dereferencing Out Of Bounds Pointer
	Dereferencing Out Of Bounds Pointer

Noncompliant Code Example (Dereferencing Out Of Bounds Pointer)

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This compliant solution is for illustrative purposes and is not necessarily the solution implemented by Microsoft. This particular "solution" may not be correct, because there is no guarantee that a L' ' is found.

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	Apparently Accessible Out Of Range Index
	Apparently Accessible Out Of Range Index

Noncompliant Code Example (Apparently Accessible Out Of Range Index)

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Code Block

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static const size_t COLS = 5;
static const size_t ROWS = 7;

static int matrix[ROWS][COLS];

void init_matrix(int x) {
  for (size_t i = 0; i != ROWS; ++i)
    for (size_t j = 0; j != COLS; ++j)
      matrix[i][j] = x;
}

Anchor

	Pointer Past Flexible Array Member
	Pointer Past Flexible Array Member

Noncompliant Code Example (Pointer Past Flexible Array Member)

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Noncompliant Code Example (Forming Out Of Bounds Pointer)

Noncompliant Code Example (Dereferencing Out Of Bounds Pointer)

Noncompliant Code Example (Apparently Accessible Out Of Range Index)

Noncompliant Code Example (Pointer Past Flexible Array Member)