[PATCH] D114718: [analyzer] Implement a new checker for Strict Aliasing Rule.

[Denys Petrov via Phabricator via cfe-commits]

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`StrictAliasingChecker` implements checks on violation of the next paragraph of the Standard which is known as **Strict Aliasing Rule**. It operates on variable loads and stores. The checker compares the original type of the value with the type of the pointer with which the value is aliased.
The paragraph:

> C++20 7.2.1 p11 [basic.lval]:
>  If a program attempts to access the stored value of an object through a glvalue whose type is not similar to one of the following types the behavior is undefined:
>
> - the dynamic type of the object,
> - a type that is the signed or unsigned type corresponding to the dynamic type of the object, or
> - a char, unsigned char, or std​::​byte type.

Example:

  int x = 42;
  auto c = *((char*)&x); // The original type is `int`. The aliased type is `char`. OK. 
  auto f = *((float*)&x); // The original type is `int`. The aliased type is `float`. UB. 


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114718

Files:
  clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
  clang/lib/StaticAnalyzer/Checkers/CMakeLists.txt
  clang/lib/StaticAnalyzer/Checkers/StrictAliasingChecker.cpp
  clang/test/Analysis/Checkers/StrictAliasingChecker/strict-aliasing.cpp

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