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Merge pull request #787 from github/lcartey/rule-10-3-bitwise
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`EssentialType`: Implement correct essential types for bitwise binary operators `&`, `^` and `|`.
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@lcartey
lcartey authored Jan 17, 2025
2 parents 70b1ed4 + eae7385 commit 8736ca7
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Showing 6 changed files with 588 additions and 71 deletions.
160 changes: 89 additions & 71 deletions c/misra/src/codingstandards/c/misra/EssentialTypes.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -31,17 +31,19 @@ class EssentialTypeCategory extends TEssentialTypeCategory {
}
}

class EssentiallySignedOrUnsignedType extends EssentialTypeCategory {
EssentiallySignedOrUnsignedType() {
this = EssentiallySignedType() or this = EssentiallyUnsignedType()
}
}

/**
* An expression in the program that evaluates to a compile time constant signed or unsigned integer.
*/
private class ConstantIntegerExpr extends Expr {
pragma[noinline]
ConstantIntegerExpr() {
getEssentialTypeCategory(this.getType()) =
[
EssentiallyUnsignedType().(EssentialTypeCategory),
EssentiallySignedType().(EssentialTypeCategory)
] and
getEssentialTypeCategory(this.getType()) instanceof EssentiallySignedOrUnsignedType and
exists(this.getValue().toFloat()) and
not this instanceof Conversion
}
Expand Down Expand Up @@ -192,8 +194,8 @@ class EssentialEqualityOperationExpr extends EssentialExpr, EqualityOperation {
override Type getEssentialType() { result instanceof BoolType }
}

class EssentialBinaryBitwiseOperationExpr extends EssentialExpr, BinaryBitwiseOperation {
EssentialBinaryBitwiseOperationExpr() {
class EssentialShiftOperationExpr extends EssentialExpr, BinaryBitwiseOperation {
EssentialShiftOperationExpr() {
this instanceof LShiftExpr or
this instanceof RShiftExpr
}
Expand Down Expand Up @@ -235,9 +237,7 @@ class EssentialUnaryPlusExpr extends EssentialExpr, UnaryPlusExpr {
operandEssentialType = getEssentialType(getOperand()) and
operandEssentialTypeCategory = getEssentialTypeCategory(operandEssentialType)
|
if
operandEssentialTypeCategory =
[EssentiallyUnsignedType().(TEssentialTypeCategory), EssentiallySignedType()]
if operandEssentialTypeCategory instanceof EssentiallySignedOrUnsignedType
then result = operandEssentialType
else result = getStandardType()
)
Expand All @@ -257,6 +257,13 @@ class EssentialUnaryMinusExpr extends EssentialExpr, UnaryMinusExpr {
}
}

bindingset[essentialTypeA, essentialTypeB]
private Type maxRankType(Type essentialTypeA, Type essentialTypeB) {
if essentialTypeA.getSize() > essentialTypeB.getSize()
then result = essentialTypeA
else result = essentialTypeB
}

class EssentialConditionalExpr extends EssentialExpr, ConditionalExpr {
override Type getEssentialType() {
exists(Type thenEssentialType, Type elseEssentialType |
Expand All @@ -267,30 +274,34 @@ class EssentialConditionalExpr extends EssentialExpr, ConditionalExpr {
then result = thenEssentialType
else
if
getEssentialTypeCategory(thenEssentialType) = EssentiallySignedType() and
getEssentialTypeCategory(elseEssentialType) = EssentiallySignedType()
then
if thenEssentialType.getSize() > elseEssentialType.getSize()
then result = thenEssentialType
else result = elseEssentialType
else
if
getEssentialTypeCategory(thenEssentialType) = EssentiallyUnsignedType() and
getEssentialTypeCategory(elseEssentialType) = EssentiallyUnsignedType()
then
if thenEssentialType.getSize() > elseEssentialType.getSize()
then result = thenEssentialType
else result = elseEssentialType
else result = this.getStandardType()
getEssentialTypeCategory(thenEssentialType) = getEssentialTypeCategory(elseEssentialType) and
getEssentialTypeCategory(thenEssentialType) instanceof EssentiallySignedOrUnsignedType
then result = maxRankType(thenEssentialType, elseEssentialType)
else result = this.getStandardType()
)
}
}

class EssentialBinaryArithmeticExpr extends EssentialExpr, BinaryArithmeticOperation {
EssentialBinaryArithmeticExpr() {
// GNU C extension has min/max which we can ignore
not this instanceof MinExpr and
not this instanceof MaxExpr
/**
* A binary operation subject to usual conversions, with essential type behaviour as specified by D.7.9.
*/
class EssentialBinaryOperationSubjectToUsualConversions extends EssentialExpr, BinaryOperation {
EssentialBinaryOperationSubjectToUsualConversions() {
this instanceof MulExpr
or
this instanceof DivExpr
or
this instanceof RemExpr
or
this instanceof AddExpr
or
this instanceof SubExpr
or
this instanceof BitwiseAndExpr
or
this instanceof BitwiseOrExpr
or
this instanceof BitwiseXorExpr
}

override Type getEssentialType() {
Expand All @@ -305,50 +316,57 @@ class EssentialBinaryArithmeticExpr extends EssentialExpr, BinaryArithmeticOpera
rightEssentialTypeCategory = getEssentialTypeCategory(rightEssentialType)
|
if
leftEssentialTypeCategory = EssentiallySignedType() and
rightEssentialTypeCategory = EssentiallySignedType()
leftEssentialTypeCategory = rightEssentialTypeCategory and
leftEssentialTypeCategory instanceof EssentiallySignedOrUnsignedType
then
if exists(getValue())
then result = stlr(this)
else (
if leftEssentialType.getSize() > rightEssentialType.getSize()
then result = leftEssentialType
else result = rightEssentialType
)
else
if
leftEssentialTypeCategory = EssentiallyUnsignedType() and
rightEssentialTypeCategory = EssentiallyUnsignedType()
then
if exists(getValue())
then result = utlr(this)
else (
if leftEssentialType.getSize() > rightEssentialType.getSize()
then result = leftEssentialType
else result = rightEssentialType
)
else
if
this instanceof AddExpr and
(
leftEssentialTypeCategory = EssentiallyCharacterType()
or
rightEssentialTypeCategory = EssentiallyCharacterType()
) and
(
leftEssentialTypeCategory =
[EssentiallySignedType(), EssentiallyUnsignedType().(TEssentialTypeCategory)]
or
rightEssentialTypeCategory =
[EssentiallySignedType(), EssentiallyUnsignedType().(TEssentialTypeCategory)]
)
or
this instanceof SubExpr and
leftEssentialTypeCategory = EssentiallyCharacterType() and
rightEssentialTypeCategory =
[EssentiallySignedType(), EssentiallyUnsignedType().(TEssentialTypeCategory)]
then result instanceof PlainCharType
else result = this.getStandardType()
leftEssentialTypeCategory = EssentiallySignedType() and result = stlr(this)
or
leftEssentialTypeCategory = EssentiallyUnsignedType() and result = utlr(this)
else result = maxRankType(leftEssentialType, rightEssentialType)
else result = this.getStandardType()
)
}
}

/**
* An add expression, with essential type behaviour as specified by D.7.9.
*/
class EssentialAddExpr extends EssentialBinaryOperationSubjectToUsualConversions, AddExpr {
override Type getEssentialType() {
exists(
EssentialTypeCategory operandTypeCategory, EssentialTypeCategory otherOperandTypeCategory
|
operandTypeCategory = getEssentialTypeCategory(getEssentialType(getAnOperand())) and
otherOperandTypeCategory = getEssentialTypeCategory(getEssentialType(getAnOperand()))
|
if
operandTypeCategory = EssentiallyCharacterType() and
otherOperandTypeCategory instanceof EssentiallySignedOrUnsignedType
then result instanceof PlainCharType
else result = super.getEssentialType()
)
}
}

/**
* A sub expression, with essential type behaviour as specified by D.7.9.
*/
class EssentialSubExpr extends EssentialBinaryOperationSubjectToUsualConversions, SubExpr {
override Type getEssentialType() {
exists(
EssentialTypeCategory leftEssentialTypeCategory,
EssentialTypeCategory rightEssentialTypeCategory
|
leftEssentialTypeCategory = getEssentialTypeCategory(getEssentialType(getLeftOperand())) and
rightEssentialTypeCategory = getEssentialTypeCategory(getEssentialType(getRightOperand()))
|
if
leftEssentialTypeCategory = EssentiallyCharacterType() and
rightEssentialTypeCategory instanceof EssentiallySignedOrUnsignedType
then result instanceof PlainCharType
else result = super.getEssentialType()
)
}
}
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