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>
- AST navigation such as `getObject` and `getChild` now only moves through nodes identified via `injects`
- identification such as `isSubscript` only holds for injected nodes
- subclasses such as `AttrNode` are injected nodes (no, say after-nodes)
The new (shared-CFG-based) Python control flow graph in
`semmle.python.controlflow.internal.Cfg` previously did not emit CFG
nodes for parameter type annotations (`def f(x: T): ...`) or for the
return type annotation (`-> T`). The legacy CFG emitted both, and a
small number of framework models rely on this: `LocalSources.qll`'s
`annotatedInstance` walks the parameter annotation expression by way
of its CFG node to track that a parameter receives an instance of the
annotated class.
After the dataflow flip to the new CFG/SSA this regression manifested
as lost flows in any test exercising annotation-based parameter
tracking: FastAPI `Depends()` receivers, Pydantic request bodies,
Starlette `WebSocket`, the call-graph type-annotation test, and so on.
Extend `FunctionDefExpr` to visit each annotation as a child of the
function-def expression, in CPython evaluation order: positional
parameter annotations, `*args` annotation, keyword-only parameter
annotations, `**kwargs` annotation, then the return annotation. (Lambda
expressions have no annotations in Python syntax, so `LambdaExpr` is
unchanged.) PEP 695 type parameters remain out of scope; they belong
to the inner annotation scope, not the enclosing CFG.
Restored test results across `framework/aiohttp`, `framework/fastapi`,
`framework/lxml`, the `CallGraph-type-annotations` test, and
`CWE-022-PathInjection`. Two FastAPI list-comprehension MISSING markers
become positive (`taint_test.py:41,55`). CPython CFG consistency
remains clean.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
The new CFG previously only emitted exception edges for explicit `raise`
and `assert` statements. As a result, code that became reachable only
via the exception path of an arbitrary expression (e.g., the body of an
`except` handler following a try-body whose `call()` could raise) was
classified as dead, breaking analyses like StackTraceExposure,
FileNotAlwaysClosed, ExceptionInfo, UseOfExit, and CatchingBaseException.
This commit adds a `mayThrow` predicate over expressions that are known
sources of implicit exceptions in Python (calls, attribute access,
subscripts, arithmetic/comparison operators, imports, await/yield/yield
from) plus `from m import *` at the statement level, and routes them
through the shared CFG's `beginAbruptCompletion(_, _, ExceptionSuccessor,
always=false)` hook.
The set of exception sources is restricted to nodes that are
syntactically inside a `try`/`with` statement in the same scope.
This mirrors Java's `ControlFlowGraph::mayThrow`, which only emits
exception edges where local handling can observe them — outside such
contexts, the edges add CFG complexity (weakening BarrierGuard
precision and breaking SSA continuity around augmented assignments and
subscript stores) without analysis benefit, since exceptions just
propagate to the function exit anyway.
Net effect on the test suite: ~100 alerts restored across the exception-
related query tests (StackTraceExposure +29, ExceptionInfo +17,
FileNotAlwaysClosed +52, UseOfExit +1, CatchingBaseException restored)
with no precision regressions. Affected `.expected` files and the
regression-guard `dead_under_no_raise.py` are updated accordingly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Adds the public facade on top of the AstNodeImpl adapter from the
previous commit. Re-exposes the same API surface as
semmle/python/Flow.qll (ControlFlowNode, CallNode, BasicBlock,
NameNode, DefinitionNode, CompareNode, ...), backed by the shared
codeql.controlflow.ControlFlowGraph library.
- semmle.python.controlflow.internal.Cfg — public facade.
- ControlFlow/store-load/* — basic store/load coverage via the facade.
The new CFG library is added additively: it has zero callers in lib/
and src/, and the legacy CFG in semmle/python/Flow.qll remains the
default. Dataflow, SSA, and production query migration land in
follow-up PRs.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
The `instanceFieldStep` disjunct of `TypeTrackingInput::levelStepCall`
that was added in 7.2.0 uses `classInstanceTracker(cls)` -- which is
itself a type-tracker -- inside `levelStepCall`. That creates a
structural mutual recursion between the main type-tracker fixpoint and
`classInstanceTracker`, causing the type-tracker delta to blow up to
~100M tuples per iteration on some OOP-heavy Python codebases.
Verified on the python/mypy database: SSRF query wall time goes from
~12s before the offending commit to >40 minutes after it.
This hotfix temporarily drops the `instanceFieldStep` disjunct and
keeps only `inheritedFieldStep`, which does not pull on the call
graph and is well-behaved (verified at ~12s on mypy). The
`instanceFieldStep` helper predicate itself is kept in place, and
the `levelStepCall` body has a commented-out call to it so the
change is trivial to re-enable once the recursion issue is properly
addressed.
Preparatory refactor for the shared-CFG dataflow migration. Adds the
adapter that mediates between the Python AST and the shared
codeql.controlflow.ControlFlowGraph signature, plus the test suites
that validate the new CFG directly against this adapter. The public
facade is added in the following commit.
Library additions:
- semmle.python.controlflow.internal.AstNodeImpl — wraps Python's
Stmt/Expr/Scope/Pattern and adds two synthetic kinds of node
(BlockStmt for body slots, intermediate nodes for multi-operand
boolean expressions) to satisfy the shared CFG signature.
- lib/ide-contextual-queries/printCfg.ql — the IDE "Print CFG" query, retargeted to the new CFG.
- consistency-queries/CfgConsistency.ql — consistency query running
the shared CFG's standard checks against Python.
Test additions (all driven directly off AstNodeImpl):
- ControlFlow/bindings/* — annotation-driven SSA-binding tests
(annassign, compound, comprehension, decorated, except_handler,
imports, match_pattern, parameters, simple, type_params,
walrus_starred, with_stmt, dead_under_no_raise).
- ControlFlow/evaluation-order/NewCfg*.ql — mirrors of the existing
OldCfg evaluation-order self-validation suite, run against the
new CFG via NewCfgImpl.qll.
- Minor extensions to existing test_if.py / test_boolean.py +
cosmetic .expected churn on a handful of OldCfg tests.
No dataflow, SSA, or production query is migrated yet.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
