[Bug c++/100210] New: [[nodiscard]] constructor causes warning on arm-linux-gnueabihf

[georg.schwab at emocean dot io]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100210

            Bug ID: 100210
           Summary: [[nodiscard]] constructor causes warning on
                    arm-linux-gnueabihf
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: georg.schwab at emocean dot io
  Target Milestone: ---
            Target: arm-linux-gnueabihf

Created attachment 50655
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50655&action=edit
offending code

The code below causes a warning under arm-linux-gnueabihf when using
-Wunused-result. Under x86_64-linux-gnu and aarch64-linux-gnu, the code
compiles without warnings.

(Tested on Ubuntu 20.04.1 LTS for x86_64)

Offending Code:
===============

struct X
{
   [[nodiscard]] X(int);
};

void t()
{
   X x(0);
}

Command Line and Output:
========================

$ arm-linux-gnueabihf-g++-10 -c -Wunused-result nodiscard-constructor.cpp
nodiscard-constructor.cpp: In function ‘void t()’:
nodiscard-constructor.cpp:8:7: warning: ignoring return value of ‘X::X(int)’,
declared with attribute ‘nodiscard’ [-Wunused-result]
    8 |  X x(0);
      |       ^
nodiscard-constructor.cpp:3:16: note: declared here
    3 |  [[nodiscard]] X(int);
      |                ^
nodiscard-constructor.cpp:8:7: warning: ignoring return value of ‘X::X(int)’,
declared with attribute ‘nodiscard’ [-Wunused-result]
    8 |  X x(0);
      |       ^
nodiscard-constructor.cpp:3:16: note: declared here
    3 |  [[nodiscard]] X(int);
      |