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b7f79f2d34
Preparatory refactor for the shared-CFG dataflow migration. Adds the new Python SSA adapter additively, without changing any production behaviour. Library additions: - semmle.python.dataflow.new.internal.SsaImpl — Python SSA implementation built on the new (shared) CFG. Mirrors the Java SSA adapter (java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll): an InputSig is defined in terms of positional (BasicBlock, int) variable references, and the shared codeql.ssa.Ssa::Make<Location, Cfg, Input> module is then instantiated. SourceVariable is the AST-level Py::Variable. Variable references are looked up via the new CFG facade's NameNode.defines/uses/deletes predicates (added in the preceding PR), which themselves are one-line bridges to AST-level Name.defines/uses/deletes. Implicit-entry definitions are inserted for non-local/global/builtin reads, captured variables, and (when needed) parameters. Test additions: - library-tests/dataflow-new-ssa/ — exercises the new SSA over a representative test corpus and checks expected def/use chains. - library-tests/dataflow-new-ssa-vs-legacy/ — runs both new SSA and legacy ESSA over the same corpus and diffs the results, so any semantic divergence shows up as a test failure. Production impact: None. The new SSA adapter has zero callers in lib/ and src/ — the legacy ESSA SSA (semmle/python/essa/*) remains the default. The dataflow library is not migrated yet; that lands in a follow-up PR. Verified by: - All 367 lib + src + consistency-queries compile clean. - All 641 ControlFlow + PointsTo + dataflow + essa + consistency library-tests pass. - Both new dataflow-new-ssa[/vs-legacy] test packs pass. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
60 lines
2.1 KiB
Plaintext
60 lines
2.1 KiB
Plaintext
/**
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* Compares the new-CFG SSA against the legacy ESSA on the same Python
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* sources. Reports definitions present in one implementation but not
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* the other, identified by variable name + source position.
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*
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* The `.expected` file records the current diff as a snapshot: as the
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* new SSA matures (closing captured-variable gap, exception bindings,
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* etc.) and tracks more variables, the snapshot should monotonically
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* shrink.
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*
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* Known categories of `def-only-old` mismatches:
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* - Function / class / global definitions with no in-scope read
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* (intentional: SSA is liveness-pruned, write-only variables are
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* not tracked).
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* - Captured / closure variables (gap: new SSA does not yet model
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* closure captures).
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* - Module variables `__name__`, `__package__`, `$` (legacy ESSA
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* adds implicit bindings the new SSA does not).
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* - Exception-handler `as` bindings (depend on raise modelling).
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*
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* `def-only-new` mismatches would indicate the new SSA produces spurious
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* definitions; currently none are expected.
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*/
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import python
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import semmle.python.dataflow.new.internal.SsaImpl as NewSsa
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import semmle.python.controlflow.internal.Cfg as Cfg
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import semmle.python.essa.Essa
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string newDefSig(NewSsa::EssaNodeDefinition def) {
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exists(Cfg::ControlFlowNode n | n = def.getDefiningNode() |
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result =
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def.getVariable().getVariable().getId() + ":" + n.getLocation().getStartLine() + ":" +
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n.getLocation().getStartColumn()
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)
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}
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string legacyDefSig(EssaNodeDefinition def) {
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exists(ControlFlowNode n | n = def.getDefiningNode() |
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result =
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def.getSourceVariable().getName() + ":" + n.getLocation().getStartLine() + ":" +
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n.getLocation().getStartColumn()
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)
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}
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from string kind, string sig
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where
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kind = "def-only-new" and
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exists(NewSsa::EssaNodeDefinition def |
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sig = newDefSig(def) and
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not exists(EssaNodeDefinition legacyDef | sig = legacyDefSig(legacyDef))
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)
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or
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kind = "def-only-old" and
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exists(EssaNodeDefinition legacyDef |
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sig = legacyDefSig(legacyDef) and
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not exists(NewSsa::EssaNodeDefinition def | sig = newDefSig(def))
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)
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select kind, sig
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