[PATCH] D150352: [clang][dataflow] Don't analyze templated declarations.

[Martin Böhme via Phabricator via cfe-commits]

mboehme created this revision.
Herald added subscribers: martong, xazax.hun.
Herald added a reviewer: NoQ.
Herald added a project: All.
mboehme requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Attempting to analyze templated code doesn't have a good cost-benefit ratio. We
have so far done a best-effort attempt at this, but maintaining this support has
an ongoing high maintenance cost because the AST for templates can violate a lot
of the invariants that otherwise hold for the AST of concrete code. As just one
example, in concrete code the operand of a UnaryOperator '*' is always a prvalue
(https://godbolt.org/z/s3e5xxMd1), but in templates this isn't true
(https://godbolt.org/z/6W9xxGvoM).

Further rationale for not analyzing templates:

- The semantics of a template itself are weakly defined; semantics can depend strongly on the concrete template arguments. Analyzing the template itself (as opposed to an instantiation) therefore has limited value.

- Analyzing templates requires a lot of special-case code that isn't necessary for concrete code because dependent types are hard to deal with and the AST violates invariants that otherwise hold for concrete code (see above).

- There's precedent in that neither Clang Static Analyzer nor the flow-sensitive warnings in Clang (such as uninitialized variables) support analyzing templates.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150352

Files:
  clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
  clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
  clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
  clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D150352.521244.patch
Type: text/x-patch
Size: 7290 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20230511/f32d2811/attachment-0001.bin>