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>
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>
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/printCfgNew.ql — debug/visualisation query for 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>
Preparatory refactor for the shared-CFG dataflow migration. Switches
'import python' to 'import python as Py' inside Flow.qll, and qualifies
every AST-class reference (Expr, Bytes, Dict, AssignExpr, Compare,
Module, Scope, Call, Attribute, SsaVariable, AugAssign, etc.) with the
Py:: prefix.
Flow.qll's own CFG types (ControlFlowNode, BasicBlock, CallNode,
NameNode, DefinitionNode, CompareNode, ...) keep their unqualified
names — they remain the public CFG API exported from this file.
This is a semantic noop: the qualification was applied mechanically by
script and no name resolution changes. Verified by:
- All 361 lib/ + src/ queries compile clean.
- All 186 ControlFlow + PointsTo + dataflow library-tests pass.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Follow-up to the getAFlowNode deprecation in the same PR: same AST→legacy-CFG
bridge pattern. The 11 internal call sites (across objects/, types/,
frameworks/, and TypeTrackingImpl) are rewritten to bind a `Return ret`
explicitly, then constrain via `ret.getScope() = f and n.getNode() = ret.getValue()`.
The predicate itself is preserved with a deprecation note so external
users do not experience churn.
Semantic noop.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Preparatory refactor for the shared-CFG dataflow migration.
Deprecates the AstNode.getAFlowNode() cached predicate on the public
Python QL API and rewrites all ~140 internal callers across lib/, src/,
test/, and tools/ from `expr.getAFlowNode() = cfgNode` to
`cfgNode.getNode() = expr`, using ControlFlowNode.getNode() which
already exists in Flow.qll.
The predicate itself is preserved (with a deprecation note pointing at
the new pattern) so external users do not experience churn — they can
migrate at their own pace and the AST/CFG hierarchies still get the
intended untangling once the deprecation eventually elapses.
Semantic noop verified by:
- All 361 lib/ + src/ queries compile clean.
- All 122 ControlFlow + PointsTo library-tests pass.
- All 64 dataflow library-tests pass.
- All 113 Variables/Exceptions/Expressions/Statements/Functions/Imports/
Security/CWE-798/ModificationOfParameterWithDefault query-tests pass.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
