C++: Remove support for global variables as sources and sinks in MaD#22089
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MathiasVP wants to merge 6 commits into
Open
C++: Remove support for global variables as sources and sinks in MaD#22089MathiasVP wants to merge 6 commits into
MathiasVP wants to merge 6 commits into
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Pull request overview
This PR removes the (previously partial/undocumented) ability for C/C++ Models-as-Data (MaD) to treat variables (global, namespace, and member variables) as flow sources/sinks, simplifying the MaD interpretation layer ahead of upcoming access-path work.
Changes:
- Drops MaD “variable-as-element” interpretation paths in the C++ MaD implementation.
- Updates the MaD C++ library tests and expected results to remove variable-based source/sink/summary cases.
- Adds a breaking change note documenting the removal.
Show a summary per file
| File | Description |
|---|---|
| cpp/ql/test/library-tests/dataflow/models-as-data/tests.cpp | Removes variable-based MaD source/sink/summary test cases (and related declarations). |
| cpp/ql/test/library-tests/dataflow/models-as-data/testModels.expected | Updates expected interpreted elements to match the removal of variable-based models. |
| cpp/ql/lib/semmle/code/cpp/dataflow/internal/FlowSummaryImpl.qll | Disables MaD input/output interpretation logic for variables. |
| cpp/ql/lib/semmle/code/cpp/dataflow/ExternalFlow.qll | Removes element-resolution support for member variables and global/namespace variables. |
| cpp/ql/lib/change-notes/2026-06-30-variables-as-mad-sources-and-sinks.md | Documents the breaking removal of variable sources/sinks in MaD. |
Review details
- Files reviewed: 5/5 changed files
- Comments generated: 3
- Review effort level: Low
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When we added MaD support for C/C++ we added (partial) support for picking variables as flow sources or flow sinks. I was never really a fan of adding this kind of support with no clear use-case for it (see my comments here and here) and in the 2 years we've had MaD support we've never had a need for this particular feature, and the only occurrence of this has been in the tests we added 2 years ago. We've also never publicly documented this feature (as it was only ever partially implemented).
I am now adding support for access paths for MaD sources and sinks (because I've got a use-case for it coming up), and this feature variables as sources and sinks are making it harder to support this.
In conclusion: I think we should just remove this feature.
DCA was uneventful (as expected).