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C++: Only add conversion when necessary.

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This commit is contained in:
Mathias Vorreiter Pedersen
2023-09-18 11:46:11 +01:00
parent 53561b7883
commit 38b100531b
1 changed files with 22 additions and 3 deletions
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25
cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedExpr.qll
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@@ -1906,8 +1906,10 @@ class TranslatedNonConstantAllocationSize extends TranslatedAllocationSize {
final override predicate hasInstruction(Opcode opcode, InstructionTag tag, CppType resultType) {
resultType = getTypeForPRValue(expr.getAllocator().getParameter(0).getType()) and
(
this.extentNeedsConversion() and
// Convert the extent to `size_t`, because the AST doesn't do this already.
tag = AllocationExtentConvertTag() and opcode instanceof Opcode::Convert
tag = AllocationExtentConvertTag() and
opcode instanceof Opcode::Convert
or
tag = AllocationElementSizeTag() and opcode instanceof Opcode::Constant
or
@@ -1918,6 +1920,7 @@ class TranslatedNonConstantAllocationSize extends TranslatedAllocationSize {
final override Instruction getInstructionSuccessor(InstructionTag tag, EdgeKind kind) {
kind instanceof GotoEdge and
(
this.extentNeedsConversion() and
tag = AllocationExtentConvertTag() and
result = this.getInstruction(AllocationElementSizeTag())
or
@@ -1933,7 +1936,9 @@ class TranslatedNonConstantAllocationSize extends TranslatedAllocationSize {
final override Instruction getChildSuccessor(TranslatedElement child) {
child = this.getExtent() and
result = this.getInstruction(AllocationExtentConvertTag())
if this.extentNeedsConversion()
then result = this.getInstruction(AllocationExtentConvertTag())
else result = this.getInstruction(AllocationElementSizeTag())
}
final override string getInstructionConstantValue(InstructionTag tag) {
@@ -1945,18 +1950,32 @@ class TranslatedNonConstantAllocationSize extends TranslatedAllocationSize {
tag = AllocationSizeTag() and
(
operandTag instanceof LeftOperandTag and
result = this.getInstruction(AllocationExtentConvertTag())
(
if this.extentNeedsConversion()
then result = this.getInstruction(AllocationExtentConvertTag())
else result = this.getExtent().getResult()
)
or
operandTag instanceof RightOperandTag and
result = this.getInstruction(AllocationElementSizeTag())
)
or
this.extentNeedsConversion() and
tag = AllocationExtentConvertTag() and
operandTag instanceof UnaryOperandTag and
result = this.getExtent().getResult()
}
TranslatedExpr getExtent() { result = getTranslatedExpr(expr.getExtent().getFullyConverted()) }
/**
* Holds if the result of `expr.getExtent()` does not have the same type as
* the allocator's size parameter.
*/
private predicate extentNeedsConversion() {
expr.getExtent().getFullyConverted().getUnspecifiedType() !=
expr.getAllocator().getParameter(0).getUnspecifiedType()
}
}
/**