C++: Data flow through reference parameters#2063
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rdmarsh2 merged 4 commits intogithub:masterfrom Oct 22, 2019
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rdmarsh2
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Oct 2, 2019
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| /** INTERNAL: do not use. The final value of a non-const ref parameter. */ | ||
| class RefParameterFinalValueNode extends Node, TRefParameterFinalValueNode { |
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Could this go in DataFlowPrivate.qll?
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Not without some restructuring. The name TRefParameterFinalValueNode is not
available outside this file.
geoffw0
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Oct 3, 2019
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LGTM, a few questions / suggestions.
cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll
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@rdmarsh2 I'm happy with this PR now. Please merge it if you are as well. |
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I think the test failures are a semantic conflict with #1735 |
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This also conflicts with #2088, hopefully in a good way. |
This merges github#1735 into this branch to resolve the semantic merge conflicts between them.
…meter I've accepted the new test output, which shows that this branch fixes two false negatives in the test cases from github#2088.
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LGTM |
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This is for a customer who reported to @AlexTereshenkov that we weren't finding all the expected flow in their project. I tested performance on the snapshot from that customer, and it looked fine.
The mechanism used to add this flow is similar to what C# does for
refandoutparameters. The main difference is that C# has explicit data-flow nodes for SSA assignments and reuses those to hold the final assigned value of an output parameter, whereas for C++ I had to addRefParameterFinalValueNodefor this purpose.This work could in principle be generalized to support pointer-typed output parameters, but that's more risky wrt. performance and false positives.
The new tests show some false positives, but none of them are related to the QL changes in this PR.