codeql/java/ql/lib/semmle/code/java/Constants.qll at codeql-cli/v2.19.2 · github/codeql · GitHub

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/**

* Provdides a module to calculate constant integer and boolean values.

import java

signature boolean getBoolValSig(Expr e);

signature int getIntValSig(Expr e);

/**

* Given predicates defining boolean and integer constants, this module

* calculates additional boolean and integer constants using only the rules that

* apply to compile-time constants.

* The input and output predicates are expected to be mutually recursive.

module CalculateConstants<getBoolValSig/1 getBoolVal, getIntValSig/1 getIntVal> {

/** Gets the value of a constant boolean expression. */

boolean calculateBooleanValue(Expr e) {

// No casts relevant to booleans.

// `!` is the only unary operator that evaluates to a boolean.

result = getBoolVal(e.(LogNotExpr).getExpr()).booleanNot()

// Handle binary expressions that have integer operands and a boolean result.

exists(BinaryExpr b, int left, int right |

b = e and

left = getIntVal(b.getLeftOperand()) and

right = getIntVal(b.getRightOperand())

(

b instanceof LTExpr and

if left < right then result = true else result = false

)

(

b instanceof LEExpr and

if left <= right then result = true else result = false

)

(

b instanceof GTExpr and

if left > right then result = true else result = false

)

(

b instanceof GEExpr and

if left >= right then result = true else result = false

)

(

b instanceof ValueOrReferenceEqualsExpr and

if left = right then result = true else result = false

)

(

b instanceof ValueOrReferenceNotEqualsExpr and

if left != right then result = true else result = false

)

// Handle binary expressions that have boolean operands and a boolean result.

exists(BinaryExpr b, boolean left, boolean right |

b = e and

left = getBoolVal(b.getLeftOperand()) and

right = getBoolVal(b.getRightOperand())

(

b instanceof ValueOrReferenceEqualsExpr and

if left = right then result = true else result = false

)

(

b instanceof ValueOrReferenceNotEqualsExpr and

if left != right then result = true else result = false

)

(b instanceof AndBitwiseExpr or b instanceof AndLogicalExpr) and

result = left.booleanAnd(right)

(b instanceof OrBitwiseExpr or b instanceof OrLogicalExpr) and

result = left.booleanOr(right)

b instanceof XorBitwiseExpr and result = left.booleanXor(right)

)

// Ternary expressions, where the `true` and `false` expressions are boolean constants.

exists(ConditionalExpr ce, boolean condition |

ce = e and

condition = getBoolVal(ce.getCondition()) and

result = getBoolVal(ce.getBranchExpr(condition))

)

// If a `Variable` is final, its value is its initializer, if it exists.

exists(Variable v | e = v.getAnAccess() and v.isFinal() |

result = getBoolVal(v.getInitializer())

)

}

/** Gets the value of a constant integer expression. */

int calculateIntValue(Expr e) {

exists(IntegralType t | e.getType() = t | t.getName().toLowerCase() != "long") and

(

exists(CastingExpr cast, int val | cast = e and val = getIntVal(cast.getExpr()) |

if cast.getType().hasName("byte")

then result = (val + 128).bitAnd(255) - 128

else

if cast.getType().hasName("short")

then result = (val + 32768).bitAnd(65535) - 32768

else

if cast.getType().hasName("char")

then result = val.bitAnd(65535)

else result = val

)

result = getIntVal(e.(PlusExpr).getExpr())

result = -getIntVal(e.(MinusExpr).getExpr())

result = getIntVal(e.(BitNotExpr).getExpr()).bitNot()

// No `int` value for `LogNotExpr`.

exists(BinaryExpr b, int v1, int v2 |

b = e and

v1 = getIntVal(b.getLeftOperand()) and

v2 = getIntVal(b.getRightOperand())

b instanceof MulExpr and result = v1 * v2

b instanceof DivExpr and result = v1 / v2

b instanceof RemExpr and result = v1 % v2

b instanceof AddExpr and result = v1 + v2

b instanceof SubExpr and result = v1 - v2

b instanceof LeftShiftExpr and result = v1.bitShiftLeft(v2)

b instanceof RightShiftExpr and result = v1.bitShiftRightSigned(v2)

b instanceof UnsignedRightShiftExpr and result = v1.bitShiftRight(v2)

b instanceof AndBitwiseExpr and result = v1.bitAnd(v2)

b instanceof OrBitwiseExpr and result = v1.bitOr(v2)

b instanceof XorBitwiseExpr and result = v1.bitXor(v2)

// No `int` value for `AndLogicalExpr` or `OrLogicalExpr`.

// No `int` value for `LTExpr`, `GTExpr`, `LEExpr`, `GEExpr`, `ValueOrReferenceEqualsExpr` or `ValueOrReferenceNotEqualsExpr`.

)

// Ternary conditional, with constant condition.

exists(ConditionalExpr ce, boolean condition |

ce = e and

condition = getBoolVal(ce.getCondition()) and

result = getIntVal(ce.getBranchExpr(condition))

)

// If a `Variable` is final, its value is its initializer, if it exists.

exists(Variable v | e = v.getAnAccess() and v.isFinal() |

result = getIntVal(v.getInitializer())

)

}

codeql/java/ql/lib/semmle/code/java/Constants.qll at codeql-cli/v2.19.2 · github/codeql · GitHub

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