[PATCH] D15448: [analyzer] SVal Visitor.

[Artem Dergachev via cfe-commits]

NoQ updated this revision to Diff 43683.
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An attempt on the .def-files.

The next step would probably be the `VisitChildren()` thing, and I'll see if it allows to refactor and simplify some code.

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Forgot to answer: I guess there are a few minor-but-good things about the visitors in our case compared in-class methods (such as `dumpToStream()`):

1. Easy to develop incrementally - no need to put stubs into all subclasses for methods we didn't yet implement.
2. Easy to create incomplete visitors (eg. we want to visit only `SVal`'s that appear as `Store` values, and we won't ever see a `MemSpaceRegion` appear as a `Store` value)
3. Cover the whole sub-class with a single method (eg. `VisitTypedValueRegion()` covers all kinds of `TypedValueRegion`'s).
4. Easy to create checker-specific traversal methods - if a particular checker needs to visit the hierarchy, it's not forced to adjust all classes.

The question in what way the visitor is better than a recursive function with a very large switch is a bit more complicated (because a visitor essentially //is// a recursive function with a very large switch); only point 3 of the above still applies. With `VisitChildren()`, however, it becomes much more convenient.

Hmm. One more thing about `VisitChildren()`: Normally such method is re-implemented in every visitor easily using child iterators. We don't, however, have fully functional iterators for `SVal`/`SymExpr`/`MemRegion` children (only partial solutions like `symbol_begin()`..`symbol_end()`), and also such iterators would need to be polymorphic around these three classes (eg. a symbol-child of a region). In fact, i can make such polymorphic iterators, and that'd probably be a more generic solution.


http://reviews.llvm.org/D15448

Files:
  docs/analyzer/DebugChecks.rst
  include/clang/StaticAnalyzer/Checkers/SValExplainer.h
  include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
  include/clang/StaticAnalyzer/Core/PathSensitive/Regions.def
  include/clang/StaticAnalyzer/Core/PathSensitive/SValVisitor.h
  include/clang/StaticAnalyzer/Core/PathSensitive/SVals.def
  include/clang/StaticAnalyzer/Core/PathSensitive/SVals.h
  include/clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h
  include/clang/StaticAnalyzer/Core/PathSensitive/Symbols.def
  lib/StaticAnalyzer/Checkers/ExprInspectionChecker.cpp
  test/Analysis/explain-svals.cpp

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