warnings about unused shared_ptr/unique_ptr comparisons

[Jonathan Wakely]

On 14/01/19 16:53 +0100, Ulrich Drepper wrote:
>This is a conservative implementation of a patch to make
>shared/unique_ptrs behave more like plain old pointers.  More about this
>in bug #88738
>
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88738
>
>The summary is
>
>- using clang, which enables a warning for unused results of all
>comparison operation, found a real bug
>
>- a library implementation is limited in scope and tedious to add
>everywhere. At this stage of gcc 9 it was the only acceptable solution,
>though
>
>- longer term there should be a warning for comparison operators.
>Possibly on by default with the possibility to disable it with an
>attribute (see the discussion in the bug).
>
>
>The patch proposed here only changes the code for C++17 and up to use
>the [[nodiscard]] attribute.  For gcc 10 we can either widen this or
>implement a better way with the help of the compiler.
>
>I ran the regression test suite and didn't see any additional failures.
>
>OK?

As it only makes changes for C++17 and up, this is OK for trunk now.
Thanks.