Problem with operator= of [[nodiscard]] class

[LPoirel]

Hi,

If I write a class with [[nodiscard]] attribute, with an operator= that returns *this by reference, I get a warning #3931: ignoring return value type with "nodiscard" attribute.

Since the nodiscard object is returned by reference and not by value, there should be no such warning.

Here is a reproducible example that produces this error on icc 18.0 to icc 2021.5 in https://godbolt.org/z/jqs41Ebrd 

struct [[nodiscard]] S {

    S& operator=(const S&) {return *this;}  // return a S by reference

};

int main(){

    S s;

    s = S{};  // warning with intel compiler

    static_cast<void>(s = S{});  // OK, the warning is silenced

}

[VidyalathaB_Intel · Accepted solution]

Hi Louis,

Thanks for reaching out to us.

The issue raised by you is reproducible when trying with icc (latest 2021.5.0) from our end as well.

Could you please try compiling with icpx/icx (latest 2022.0) compiler instead?

It is working as expected without throwing any such warnings when we tried it from our end.

Also, Intel Classic Compiler will enter "Legacy Product Support" mode, signaling the end of regular updates. Please refer to the article below for more details.

https://www.intel.com/content/www/us/en/developer/articles/technical/adoption-of-llvm-complete-icx.html

Regards,

Vidya.

[VidyalathaB_Intel]

Hi Louis,

Reminder:

Has the information provided helped? Please let us know if you have any updates regarding the query.

Regards,

Vidya.

[LPoirel]

Hi Vidya,

Indeed, everything is fine with icpx/icx  2022.0

Thanks for your answer.

Regards,

Louis

[VidyalathaB_Intel]

Hi Louis,

Thanks for accepting our solution.

As the issue is resolved we are closing this thread. Please post a new question if you need any additional information from Intel as this thread will no longer be monitored.

Have a Nice Day!

Regards,

Vidya.