[PATCH] D44883: [Sema] Extend -Wself-assign and -Wself-assign-field to warn on overloaded self-assignment (classes)

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added a comment.

In https://reviews.llvm.org/D44883#1054326, @thakis wrote:

> In https://reviews.llvm.org/D44883#1048751, @dblaikie wrote:
>
> > Historically Clang's policy on warnings was, I think, much more
> >  conservative than it seems to be today. There was a strong desire not to
> >  implement off-by-default warnings, and to have warnings with an
> >  exceptionally low false-positive rate - maybe the user-defined operator
> >  detection was either assumed to, or demonstrated to, have a sufficiently
> >  high false positive rate to not meet that high bar.
>
>
> This is still the case. For a new warning, you should evaluate some large open-source codebase and measure true positive and false positive rate and post the numbers here.


Just finished running it on chrome: (wow, that took a while!)

  $ cat /tmp/test.cpp 
  struct S {};
  
  void test (S a) {
    a = a;
  }
  $ /build/llvm-build-Clang-release/bin/clang++ -c /tmp/test.cpp -Wall
  /tmp/test.cpp:4:5: warning: explicitly assigning value of variable of type 'S' to itself [-Wself-assign]
    a = a;
    ~ ^ ~
  1 warning generated.
  $ ninja -C out/ClangStage2 chrome
  ninja: Entering directory `out/ClangStage2'
  [31309/31309] LINK ./chrome

Config: F5937598: args.gn <https://reviews.llvm.org/F5937598>

So unless the config ^ is wrong, there have been no occurrences, no false-positives.

Down to one [trivial] prerequisite - https://reviews.llvm.org/D45082 - would be super nice if someone could review/accept it :)


Repository:
  rC Clang

https://reviews.llvm.org/D44883