[PATCH] D156312: [analyzer] Upstream BitwiseShiftChecker

[Donát Nagy via Phabricator via cfe-commits]

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This commit releases a checker that was developed to a stable level in the Ericsson-internal fork of Clang Static Analyzer.

Note that the functionality of this checker overlaps with core.UndefinedBinaryOperatorResult ("UBOR"), but there are several differences between them:
(1) UBOR is only triggered when the constant folding performed by the Clang Static Analyzer engine determines that the value of a binary
operator expression is undefined; this checker can report issues where the operands are not constants.
(2) UBOR has unrelated checks for handling other binary operators, this checker only examines bitwise shifts.
(3) This checker has a Pedantic flag and by default does not report expressions (e.g. -2 << 2) that're undefined by the standard but consistently supported in practice.
(4) UBOR exhibits buggy behavior in code that involves cast expressions, e.g.

  void foo(unsigned short s) {
    if (s == 2) {
      (void) ((unsigned int) s) << 16;
    }
  }

Later it would be good to eliminate this overlap (perhaps by deprecating and then eliminating the bitwise shift handling in UBOR), but in my opinion that that belongs to separate commits.

Co-authored-by: Endre Fulop <endre.fulop at sigmatechnology.se>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156312

Files:
  clang/docs/analyzer/checkers.rst
  clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
  clang/lib/StaticAnalyzer/Checkers/BitwiseShiftChecker.cpp
  clang/lib/StaticAnalyzer/Checkers/CMakeLists.txt
  clang/test/Analysis/analyzer-config.c
  clang/test/Analysis/analyzer-enabled-checkers.c
  clang/test/Analysis/bitwise-ops-nocrash.c
  clang/test/Analysis/bitwise-ops.c
  clang/test/Analysis/bitwise-shift-common.c
  clang/test/Analysis/bitwise-shift-pedantic.c
  clang/test/Analysis/bitwise-shift-sanity-checks.c
  clang/test/Analysis/bitwise-shift-state-update.c
  clang/test/Analysis/casts.c
  clang/test/Analysis/diagnostics/track_subexpressions.cpp
  clang/test/Analysis/left-shift-cxx2a.cpp
  clang/test/Analysis/std-c-library-functions-arg-enabled-checkers.c
  clang/test/Analysis/symbol-simplification-nonloc-loc.cpp

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