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C++: Slightly refactor certainty computation with a newtype.

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Mathias Vorreiter Pedersen
2026-05-12 11:47:25 +01:00
parent 6d5d57acca
commit fc80a2472d
1 changed files with 40 additions and 7 deletions
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47
cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImplCommon.qll
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@@ -147,7 +147,7 @@ abstract class Indirection extends Type {
*
* `certain` is `true` if this write is guaranteed to write to the address.
*/
predicate isAdditionalWrite(Node0Impl value, Operand address, boolean certain) { none() }
predicate isAdditionalWrite(Node0Impl value, Operand address, Certainty certain) { none() }
/**
* Gets the base type of this indirection, after specifiers have been deeply
@@ -198,11 +198,11 @@ private module IteratorIndirections {
baseType = super.getValueType()
}
override predicate isAdditionalWrite(Node0Impl value, Operand address, boolean certain) {
override predicate isAdditionalWrite(Node0Impl value, Operand address, Certainty certain) {
exists(CallInstruction call | call.getArgumentOperand(0) = value.asOperand() |
this = call.getStaticCallTarget().(Function).getClassAndName("operator=") and
address = call.getThisArgumentOperand() and
certain = false
certain instanceof AlwaysUncertain
)
}
@@ -271,10 +271,41 @@ predicate isDereference(Instruction deref, Operand address, boolean additional)
additional = false
}
predicate isWrite(Node0Impl value, Operand address, boolean certain) {
private newtype TCertainty =
TCertainWhenAddressIsCertain() or
TAlwaysCertain() or
TAlwaysUncertain()
abstract private class Certainty extends TCertainty {
abstract predicate isCertain(boolean addressIsCertain);
abstract string toString();
}
private class CertainWhenAddressIsCertain extends Certainty, TCertainWhenAddressIsCertain {
override predicate isCertain(boolean addressIsCertain) { addressIsCertain = true }
override string toString() { result = "CertainWhenAddressIsCertain" }
}
private class AlwaysCertain extends Certainty, TAlwaysCertain {
override predicate isCertain(boolean addressIsCertain) {
addressIsCertain = true or addressIsCertain = false
}
override string toString() { result = "AlwaysCertain" }
}
private class AlwaysUncertain extends Certainty, TAlwaysUncertain {
override predicate isCertain(boolean addressIsCertain) { none() }
override string toString() { result = "AlwaysUncertain" }
}
predicate isWrite(Node0Impl value, Operand address, Certainty certain) {
any(Indirection ind).isAdditionalWrite(value, address, certain)
or
certain = true and
certain instanceof CertainWhenAddressIsCertain and
(
exists(StoreInstruction store |
value.asInstruction() = store and
@@ -718,16 +749,18 @@ private module Cached {
int indirectionIndex
) {
exists(
boolean writeIsCertain, boolean addressIsCertain, int ind0, CppType type, int lower, int upper
Certainty writeIsCertain, boolean addressIsCertain, int ind0, CppType type, int lower,
int upper
|
isWrite(value, address, writeIsCertain) and
isDefImpl(address, base, ind0, addressIsCertain) and
certain = writeIsCertain.booleanAnd(addressIsCertain) and
type = getLanguageType(address) and
upper = countIndirectionsForCppType(type) and
ind = ind0 + [lower .. upper] and
indirectionIndex = ind - (ind0 + lower) and
lower = getMinIndirectionsForType(any(Type t | type.hasUnspecifiedType(t, _)))
|
if writeIsCertain.isCertain(addressIsCertain) then certain = true else certain = false
)
}