[PATCH] D84898: clang-tidy] Add new checker for complex conditions with no meaning

[Vince Bridgers via Phabricator via cfe-commits]

vabridgers created this revision.
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This checker finds cases where relational expressions have no meaning.
For example, (x <= y <= z) has no meaning, but just happens to parse to
something deterministic. (x <= y <= z) is parsed to ((x <= y) <= z).
The (x<=y) returns a boolean value which is promoted to an integral
context, 0 (for false) or 1 (for true). So when (x <= y) the expression
becomes (1 <= z) and when (x > y) the expression becomes (0 <= z). When
asked to give all warnings, gcc warns about this. While this may be the
intention in some programming contexts, it may not have been what the
programmer really wanted in all contexts. So it's best to implement this as a
tidy check to start with, get some experience using it, then perhaps promote
this check to a diagnostic.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84898

Files:
  clang-tools-extra/clang-tidy/misc/CMakeLists.txt
  clang-tools-extra/clang-tidy/misc/ComplexConditionsCheck.cpp
  clang-tools-extra/clang-tidy/misc/ComplexConditionsCheck.h
  clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp
  clang-tools-extra/docs/ReleaseNotes.rst
  clang-tools-extra/docs/clang-tidy/checks/list.rst
  clang-tools-extra/docs/clang-tidy/checks/misc-complex-conditions.rst
  clang-tools-extra/test/clang-tidy/checkers/misc-complex-conditions.c

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