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EssentialType: Implement correct essential types for bitwise binary operators &, ^ and |. #787

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EssentialType: Implement correct essential types for bitwise binary operators &, ^ and |. #787

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8f81b4e
EssentialTypes: Correct handling of bitwise binary expressions
lcartey Oct 27, 2024
a5ed461
EssentialTypes: Add test cases for shifts
lcartey Oct 27, 2024
aba9528
RULE-10-3: Expand test cases for binary bitwise operators
lcartey Oct 27, 2024
5b753e0
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lcartey Oct 28, 2024
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49 changes: 47 additions & 2 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 @@ -192,8 +192,8 @@ 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 @@ -353,6 +353,51 @@ class EssentialBinaryArithmeticExpr extends EssentialExpr, BinaryArithmeticOpera
}
}

class EssentialBinaryBitwiseExpr extends EssentialExpr, BinaryBitwiseOperation {
EssentialBinaryBitwiseExpr() {
not this instanceof LShiftExpr and
not this instanceof RShiftExpr
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Any concern here about future updates to the characteristic predicate of EssentialShiftOperationExpr that aren't matched here (and vice versa)? In theory we could not find certain expressions to analyze, or worse, return two results from the overriden member predicates.

It may be better to entangle them here, eg, not this instanceof EssentialBinaryBitwiseOperationExpr

}

override Type getEssentialType() {
exists(
Type leftEssentialType, Type rightEssentialType,
EssentialTypeCategory leftEssentialTypeCategory,
EssentialTypeCategory rightEssentialTypeCategory
|
leftEssentialType = getEssentialType(getLeftOperand()) and
rightEssentialType = getEssentialType(getRightOperand()) and
leftEssentialTypeCategory = getEssentialTypeCategory(leftEssentialType) and
rightEssentialTypeCategory = getEssentialTypeCategory(rightEssentialType)
|
if
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Looks like this is now the third occurrence of this pattern, may be worth creating some kind of predicate to deduplicate this/reduce the bloat. Perhaps something like coalesce<stlr>(this, leftEssentialType, rightEssentialType, EssentiallySignedType()), even just bothSigned(leftEssentialType, rightEssentialType) could reduce the boilerplate. And it might be worthy of a bigger hammer such as Type standardCombine(Expr e, Expr operandA, Expr operandB)

leftEssentialTypeCategory = EssentiallySignedType() and
rightEssentialTypeCategory = EssentiallySignedType()
then
if exists(getValue())
then result = stlr(this)
else (
if leftEssentialType.getSize() > rightEssentialType.getSize()
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It seems we should have a predicate Type maxRank(Type a, Type b) to simplify this repetition

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 result = this.getStandardType()
)
}
}

/**
* A named Enum type, as per D.5.
*/
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