[PATCH] D41655: [clang-tidy] New check bugprone-unused-return-value

[Kalle Huttunen via Phabricator via cfe-commits]

khuttun added inline comments.


================
Comment at: test/clang-tidy/bugprone-unused-return-value.cpp:163
+
+void noWarning() {
+  auto AsyncRetval1 = std::async(increment, 42);
----------------
aaron.ballman wrote:
> khuttun wrote:
> > aaron.ballman wrote:
> > > Sorry, I just realized that we're missing a test case for a common situation -- where the result is used as part of another call expression. Can you add a test to `noWarning()` to make sure this does not warn:
> > > ```
> > > std::vector<int> v;
> > > extern void f(bool);
> > > 
> > > f(v.empty()); // Should not warn
> > > ```
> > See line 199 in this file.
> Ah, my eyes missed that, thank you!
> 
> Hmm, I *think* this test should also be okay, but I want to be sure:
> ```
> std::vector<int> v;
> bool b = ({v.empty()}); // Should not warn
> ({v.empty()}); // ???
> ```
> I kind of thing that, as an extension to the spirit of this check, any GNU expression statement whose result is unused should probably be diagnosed; what do you think?
> 
> You should add tests for the above so we document the expected behavior here.
Getting a warning when just surrounding the call expression with parenthesis is tested in bugprone-unused-return-value-custom.cpp.

Would your example be parsed as creating an initializer_list? In that case it should not warn. I can add test cases for that.

What do you mean by "GNU expression"?


https://reviews.llvm.org/D41655