[PATCH] D87455: Restrict UnnecessaryCopyInitialization check to variables initialized from methods/functions without arguments

[Felix Berger via Phabricator via cfe-commits]

flx created this revision.
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This restriction avoids cases where an alias is returned to an argument and which could lead to to a false positive change. Example:

  struct S {
    S(const S&);
    void modify();
  };
  
  const S& alias(const S& a) {
    return a;
  }
  
  void f(S a) {
    const S c = alias(a);
    a.modify();
  }

Taking a const reference of the return value of alias would not be safe since a is modified.

Still allow methods and functions with default arguments if they are called with their default arguments.

A more involved alternative approach would be to inspect each argument passed to these functions for its constness, but this can get complex quickly.

As I'm writing this I'm realizing though that this precludes catching repeated protobuff messages:

  Message m;
  const auto field = m.repeated_field(0);

Maybe this approach should be refined to allowing functions and methods that take all parameters by value?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D87455

Files:
  clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp
  clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.h
  clang-tools-extra/test/clang-tidy/checkers/performance-unnecessary-copy-initialization.cpp

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