Re: [PATCH] PR libstdc++/80316 make promise::set_value throw no_state error

[Christophe Lyon <christophe dot lyon at linaro dot org>]

On 11 July 2017 at 14:39, Jonathan Wakely <jwakely@redhat.com> wrote:
> On 11/07/17 12:53 +0100, Jonathan Wakely wrote:
>>
>> On 21/04/17 15:54 +0100, Jonathan Wakely wrote:
>>>
>>> On 4 April 2017 at 20:44, Jonathan Wakely wrote:
>>>>
>>>> We got a bug report from a customer pointing out that calling
>>>> promise::set_value on a moved-from promise crashes instead of throwing
>>>> an exception with error code future_errc::no_state.
>>>>
>>>> This fixes it, by moving the _S_check calls to *before* we deference
>>>> the pointer that the calls check!
>>>>
>>>> This passes all tests, including the more comprehensive ones I've
>>>> added as part of this commit, but I think it can wait for stage 1
>>>> anyway. We've been shipping this bug for a couple of releases already.
>>>>
>>>>        PR libstdc++/80316
>>>>        * include/std/future (_State_baseV2::_Setter::operator()): Remove
>>>>        _S_check calls that are done after the pointer to the shared
>>>> state
>>>> is
>>>>        already dereferenced.
>>>>        (_State_baseV2::_Setter<_Res, void>): Define specialization for
>>>> void
>>>>        as partial specialization so it can be defined within the
>>>> definition
>>>>        of _State_baseV2.
>>>>        (_State_baseV2::__setter): Call _S_check.
>>>>        (_State_baseV2::__setter(promise<void>*)): Add overload for use
>>>> by
>>>>        promise<void>::set_value and
>>>> promise<void>::set_value_at_thread_exit.
>>>>        (promise<T>, promise<T&>, promise<void>): Make _State a friend.
>>>>        (_State_baseV2::_Setter<void, void>): Remove explicit
>>>> specialization.
>>>>        (promise<void>::set_value,
>>>> promise<void>::set_value_at_thread_exit):
>>>>        Use new __setter overload.
>>>>        * testsuite/30_threads/promise/members/at_thread_exit2.cc: New
>>>> test.
>>>>        * testsuite/30_threads/promise/members/set_exception.cc: Test
>>>>        promise<T&> and promise<void> specializations.
>>>>        * testsuite/30_threads/promise/members/set_exception2.cc:
>>>> Likewise.
>>>>        Test for no_state error condition.
>>>>        * testsuite/30_threads/promise/members/set_value2.cc: Likewise.
>>>
>>>
>>>
>>> This is now committed to trunk.
>>
>>
>> And now also to gcc-7-branch.
>
>
> And gcc-6-branch.
>

Hi Jonathan,

The new test fails to compile on arm when forcing -march=armv5t:
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:
In function 'void test01()':^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:31:
error: aggregate 'std::promise<int> p1' has incomplete type and cannot
be defined^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:44:
error: 'make_exception_ptr' is not a member of 'std'^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:52:
error: variable 'std::promise<int> p2' has initializer but incomplete
type^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:64:
error: 'make_exception_ptr' is not a member of 'std'^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:
In function 'void test02()':^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:75:
error: aggregate 'std::promise<int&> p1' has incomplete type and
cannot be defined^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:89:
error: 'make_exception_ptr' is not a member of 'std'^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:97:
error: variable 'std::promise<int&> p2' has initializer but incomplete
type^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:110:
error: 'make_exception_ptr' is not a member of 'std'^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:
In function 'void test03()':^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:121:
error: aggregate 'std::promise<void> p1' has incomplete type and
cannot be defined^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:134:
error: 'make_exception_ptr' is not a member of 'std'^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:142:
error: variable 'std::promise<void> p2' has initializer but incomplete
type^M
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/testsuite/30_threads/promise/members/at_thread_exit2.cc:153:
error: 'make_exception_ptr' is not a member of 'std'^M
compiler exited with status 1

I can see this on target arm-none-linux-gnueabihf --with-mode arm
--with-cpu cortex-a9 --with-fpu vfp and setting -march=armv5t in
runtestflags.

It also looks like you forgot to add a ChangeLog entry for the
testsuite changes.

There is no such error on the gcc-7 branch.

Thanks,

Christophe