Hi Jonathan, Gentle ping.
Thanks, Soumya > On 19 Jan 2026, at 8:01 PM, Soumya AR <[email protected]> wrote: > > Hi Jonathan, > > I removed the changes from stdatomic.h. > Putting an updated patch up. > Should be OK to commit without the builtins for now? > > >> On 16 Jan 2026, at 6:51 PM, Jonathan Wakely <[email protected]> wrote: >> >> External email: Use caution opening links or attachments >> >> >> On Fri, 16 Jan 2026 at 08:28, Soumya AR <[email protected]> wrote: >>>>> +// This file is part of the GNU ISO C++ Library. This library is free >>>>> +// software; you can redistribute it and/or modify it under the >>>>> +// terms of the GNU General Public License as published by the >>>>> +// Free Software Foundation; either version 3, or (at your option) >>>>> +// any later version. >>>>> + >>>>> +// This library is distributed in the hope that it will be useful, >>>>> +// but WITHOUT ANY WARRANTY; without even the implied warranty of >>>>> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >>>>> +// GNU General Public License for more details. >>>>> + >>>>> +// Under Section 7 of GPL version 3, you are granted additional >>>>> +// permissions described in the GCC Runtime Library Exception, version >>>>> +// 3.1, as published by the Free Software Foundation. >>>>> + >>>>> +// You should have received a copy of the GNU General Public License and >>>>> +// a copy of the GCC Runtime Library Exception along with this program; >>>>> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see >>>>> +// <http://www.gnu.org/licenses/>. >>>>> + >>>>> +// { dg-do run { target c++26 } } >>>> >>>> Do these new tests need { dg-add-options libatomic } ? I think they >>>> probably do. >>>> >>>> What about { dg-require-atomic-cmpxchg-word "" } ? >>> >>> Yes, you're right, ideally should have both directives. >>> >>> However, on re-working this patch, I don't think these tests are needed in >>> libstdc++ at all. I already have correctness tests for the builtins in the >>> GCC testsuite. >>> >>> To test the API, I've created a C++26 version of nonmembers.cc for >>> fetch_min/max. >>> And another fetch_min/max version for the correctness tests for atomic_ref. >> >> I missed this part, sorry. >> >> I think the new tests make sense in libstdc++. The builtins might be >> thouroughly tested in the compiler tests, but having library tests >> ensures we don't make a silly mistake like calling __atomic_fetch_min >> from the fetch_max function (an easy copy*paste error to make when >> refactoring). >> >> The tests in the new patch are adequate for that purpose: each >> function is called at least once and the expected result is verified. >> >>> Or for both of these, should we just update the existing tests to C++26? >> >> I think it's better to have separate tests for the new members, >> because the existing tests are typically only run for the default -std >> mode (currently gnu++20) and so would not test any parts of the file >> guarded by #if __cpp_lib_atomic_min_max. Having a separate test with { >> target c++26 } means that everybody who runs the testsuite will run >> that test. >> >> And we don't want to add { target c++26 } to the existing tests, >> because then we would not test that the C++11 features still work in >> C++11. >> > > Oh right, that makes more sense. I was not sure why we don't add > { target c++26 } to the existing tests earlier. Thanks for answering > this. > >>> What about c_compat.cc? >> >> No changes to that file, because there should be no changes to <stdatomic.h> >> >> >>> >>> Thanks, >>> Soumya >>> >>>>> +#include <atomic> >>>>> +#include <limits> >>>>> +#include <testsuite_hooks.h> >>>>> + >>>>> +template<typename T> >>>>> +void test_signed() >>>>> +{ >>>>> + std::atomic<T> a; >>>>> + const std::memory_order mo = std::memory_order_relaxed; >>>>> + T expected = 0; >>>>> + T value = 0; >>>>> + >>>>> + a.store(100); >>>>> + value = a.fetch_min(50); >>>>> + VERIFY( value == 100 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_min(75, mo); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_min(25); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 25 ); >>>>> + >>>>> + a.store(-10); >>>>> + value = a.fetch_min(-20); >>>>> + VERIFY( value == -10 ); >>>>> + VERIFY( a.load() == -20 ); >>>>> + >>>>> + value = a.fetch_min(-5, mo); >>>>> + VERIFY( value == -20 ); >>>>> + VERIFY( a.load() == -20 ); >>>>> + >>>>> + a.store(10); >>>>> + value = a.fetch_min(-5); >>>>> + VERIFY( value == 10 ); >>>>> + VERIFY( a.load() == -5 ); >>>>> + >>>>> + a.store(20); >>>>> + value = a.fetch_max(50); >>>>> + VERIFY( value == 20 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_max(30, mo); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_max(100); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 100 ); >>>>> + >>>>> + a.store(-50); >>>>> + value = a.fetch_max(-20); >>>>> + VERIFY( value == -50 ); >>>>> + VERIFY( a.load() == -20 ); >>>>> + >>>>> + value = a.fetch_max(-10, mo); >>>>> + VERIFY( value == -20 ); >>>>> + VERIFY( a.load() == -10 ); >>>>> + >>>>> + a.store(-10); >>>>> + value = a.fetch_max(5); >>>>> + VERIFY( value == -10 ); >>>>> + VERIFY( a.load() == 5 ); >>>>> + >>>>> + T min_val = std::numeric_limits<T>::min(); >>>>> + T max_val = std::numeric_limits<T>::max(); >>>>> + >>>>> + a.store(0); >>>>> + value = a.fetch_min(min_val); >>>>> + VERIFY( value == 0 ); >>>>> + VERIFY( a.load() == min_val ); >>>>> + >>>>> + a.store(0); >>>>> + value = a.fetch_max(max_val); >>>>> + VERIFY( value == 0 ); >>>>> + VERIFY( a.load() == max_val ); >>>>> +} >>>>> + >>>>> +template<typename T> >>>>> +void test_unsigned() >>>>> +{ >>>>> + std::atomic<T> a; >>>>> + const std::memory_order mo = std::memory_order_relaxed; >>>>> + T expected = 0; >>>>> + T value = 0; >>>>> + >>>>> + a.store(100); >>>>> + value = a.fetch_min(50); >>>>> + VERIFY( value == 100 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_min(75, mo); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_min(25); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 25 ); >>>>> + >>>>> + a.store(20); >>>>> + value = a.fetch_max(50); >>>>> + VERIFY( value == 20 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_max(30, mo); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + value = a.fetch_max(100); >>>>> + VERIFY( value == 50 ); >>>>> + VERIFY( a.load() == 100 ); >>>>> + >>>>> + T min_val = std::numeric_limits<T>::min(); >>>>> + T max_val = std::numeric_limits<T>::max(); >>>>> + >>>>> + a.store(10); >>>>> + value = a.fetch_min(min_val); >>>>> + VERIFY( value == 10 ); >>>>> + VERIFY( a.load() == min_val ); >>>>> + >>>>> + a.store(10); >>>>> + value = a.fetch_max(max_val); >>>>> + VERIFY( value == 10 ); >>>>> + VERIFY( a.load() == max_val ); >>>>> +} >>>>> + >>>>> +int main() >>>>> +{ >>>>> + test_signed<signed char>(); >>>>> + test_signed<short>(); >>>>> + test_signed<int>(); >>>>> + test_signed<long>(); >>>>> + test_signed<long long>(); >>>>> + >>>>> + test_unsigned<unsigned char>(); >>>>> + test_unsigned<unsigned short>(); >>>>> + test_unsigned<unsigned int>(); >>>>> + test_unsigned<unsigned long>(); >>>>> + test_unsigned<unsigned long long>(); >>>>> + >>>>> + return 0; >>>>> +} >>>>> \ No newline at end of file >>>>> diff --git >>>>> a/libstdc++-v3/testsuite/29_atomics/atomic_integral/fetch_minmax_order.cc >>>>> b/libstdc++-v3/testsuite/29_atomics/atomic_integral/fetch_minmax_order.cc >>>>> new file mode 100644 >>>>> index 00000000000..3ed6f2e2e6f >>>>> --- /dev/null >>>>> +++ >>>>> b/libstdc++-v3/testsuite/29_atomics/atomic_integral/fetch_minmax_order.cc >>>>> @@ -0,0 +1,116 @@ >>>>> +// Copyright The GNU Toolchain Authors. >>>>> +// >>>>> +// This file is part of the GNU ISO C++ Library. This library is free >>>>> +// software; you can redistribute it and/or modify it under the >>>>> +// terms of the GNU General Public License as published by the >>>>> +// Free Software Foundation; either version 3, or (at your option) >>>>> +// any later version. >>>>> + >>>>> +// This library is distributed in the hope that it will be useful, >>>>> +// but WITHOUT ANY WARRANTY; without even the implied warranty of >>>>> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >>>>> +// GNU General Public License for more details. >>>>> + >>>>> +// Under Section 7 of GPL version 3, you are granted additional >>>>> +// permissions described in the GCC Runtime Library Exception, version >>>>> +// 3.1, as published by the Free Software Foundation. >>>>> + >>>>> +// You should have received a copy of the GNU General Public License and >>>>> +// a copy of the GCC Runtime Library Exception along with this program; >>>>> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see >>>>> +// <http://www.gnu.org/licenses/>. >>>>> + >>>>> +// { dg-do run { target c++26 } } >>>>> + >>>>> +#include <atomic> >>>>> +#include <testsuite_hooks.h> >>>>> + >>>>> +void test_memory_orderings() >>>>> +{ >>>>> + std::atomic<int> a; >>>>> + int v; >>>>> + >>>>> + a.store(100); >>>>> + v = a.fetch_min(50, std::memory_order_relaxed); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a.load(std::memory_order_relaxed) == 50 ); >>>>> + >>>>> + a.store(100); >>>>> + v = a.fetch_min(50, std::memory_order_consume); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(100); >>>>> + v = a.fetch_min(50, std::memory_order_acquire); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(100); >>>>> + v = a.fetch_min(50, std::memory_order_release); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(100); >>>>> + v = a.fetch_min(50, std::memory_order_acq_rel); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(100); >>>>> + v = a.fetch_min(50, std::memory_order_seq_cst); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(20); >>>>> + v = a.fetch_max(50, std::memory_order_relaxed); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a.load(std::memory_order_relaxed) == 50 ); >>>>> + >>>>> + a.store(20); >>>>> + v = a.fetch_max(50, std::memory_order_consume); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(20); >>>>> + v = a.fetch_max(50, std::memory_order_acquire); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(20); >>>>> + v = a.fetch_max(50, std::memory_order_release); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(20); >>>>> + v = a.fetch_max(50, std::memory_order_acq_rel); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> + >>>>> + a.store(20); >>>>> + v = a.fetch_max(50, std::memory_order_seq_cst); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a.load() == 50 ); >>>>> +} >>>>> + >>>>> +// Test volatile atomic operations >>>>> +void test_volatile() >>>>> +{ >>>>> + volatile std::atomic<int> va; >>>>> + int v; >>>>> + >>>>> + va.store(100); >>>>> + v = va.fetch_min(50); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( va.load() == 50 ); >>>>> + >>>>> + va.store(20); >>>>> + v = va.fetch_max(50, std::memory_order_relaxed); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( va.load() == 50 ); >>>>> +} >>>>> + >>>>> +int main() >>>>> +{ >>>>> + test_memory_orderings(); >>>>> + test_volatile(); >>>>> + return 0; >>>>> +} >>>>> \ No newline at end of file >>>>> diff --git >>>>> a/libstdc++-v3/testsuite/29_atomics/atomic_integral/nonmembers.cc >>>>> b/libstdc++-v3/testsuite/29_atomics/atomic_integral/nonmembers.cc >>>>> index a07d9700ff4..3fb86db65b1 100644 >>>>> --- a/libstdc++-v3/testsuite/29_atomics/atomic_integral/nonmembers.cc >>>>> +++ b/libstdc++-v3/testsuite/29_atomics/atomic_integral/nonmembers.cc >>>>> @@ -111,6 +111,22 @@ test01() >>>>> static_assert( std::is_same<decltype(r37), int>::value, "" ); >>>>> auto r38 = atomic_fetch_xor_explicit(&a, l, mo); >>>>> static_assert( std::is_same<decltype(r38), long>::value, "" ); >>>>> + auto r39 = atomic_fetch_min(&v, i); >>>>> + static_assert( std::is_same<decltype(r39), int>::value, "" ); >>>>> + auto r40 = atomic_fetch_min(&a, l); >>>>> + static_assert( std::is_same<decltype(r40), long>::value, "" ); >>>>> + auto r41 = atomic_fetch_min_explicit(&v, i, mo); >>>>> + static_assert( std::is_same<decltype(r41), int>::value, "" ); >>>>> + auto r42 = atomic_fetch_min_explicit(&a, l, mo); >>>>> + static_assert( std::is_same<decltype(r42), long>::value, "" ); >>>>> + auto r43 = atomic_fetch_max(&v, i); >>>>> + static_assert( std::is_same<decltype(r43), int>::value, "" ); >>>>> + auto r44 = atomic_fetch_max(&a, l); >>>>> + static_assert( std::is_same<decltype(r44), long>::value, "" ); >>>>> + auto r45 = atomic_fetch_max_explicit(&v, i, mo); >>>>> + static_assert( std::is_same<decltype(r45), int>::value, "" ); >>>>> + auto r46 = atomic_fetch_max_explicit(&a, l, mo); >>>>> + static_assert( std::is_same<decltype(r46), long>::value, "" ); >>>>> } >>>>> >>>>> void >>>>> @@ -160,4 +176,12 @@ test02() >>>>> atomic_fetch_xor(&a, i); >>>>> atomic_fetch_xor_explicit(&v, i, mo); >>>>> atomic_fetch_xor_explicit(&a, i, mo); >>>>> + atomic_fetch_min(&v, i); >>>>> + atomic_fetch_min(&a, i); >>>>> + atomic_fetch_min_explicit(&v, i, mo); >>>>> + atomic_fetch_min_explicit(&a, i, mo); >>>>> + atomic_fetch_max(&v, i); >>>>> + atomic_fetch_max(&a, i); >>>>> + atomic_fetch_max_explicit(&v, i, mo); >>>>> + atomic_fetch_max_explicit(&a, i, mo); >>>>> } >>>>> diff --git a/libstdc++-v3/testsuite/29_atomics/atomic_ref/integral.cc >>>>> b/libstdc++-v3/testsuite/29_atomics/atomic_ref/integral.cc >>>>> index 310434cefb5..5a282320bd7 100644 >>>>> --- a/libstdc++-v3/testsuite/29_atomics/atomic_ref/integral.cc >>>>> +++ b/libstdc++-v3/testsuite/29_atomics/atomic_ref/integral.cc >>>>> @@ -155,9 +155,38 @@ test01() >>>>> v = a ^= 0x121; >>>>> VERIFY( v == 0x022 ); >>>>> VERIFY( a == 0x022 ); >>>>> + >>>>> + >>>>> + a = 100; >>>>> + v = a.fetch_min(50); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a == 50 ); >>>>> + >>>>> + v = a.fetch_min(75, mo); >>>>> + VERIFY( v == 50 ); >>>>> + VERIFY( a == 50 ); >>>>> + >>>>> + a = -10; >>>>> + v = a.fetch_min(-20); >>>>> + VERIFY( v == -10 ); >>>>> + VERIFY( a == -20 ); >>>>> + >>>>> + a = 20; >>>>> + v = a.fetch_max(50); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a == 50 ); >>>>> + >>>>> + v = a.fetch_max(30, mo); >>>>> + VERIFY( v == 50 ); >>>>> + VERIFY( a == 50 ); >>>>> + >>>>> + a = -50; >>>>> + v = a.fetch_max(-20); >>>>> + VERIFY( v == -50 ); >>>>> + VERIFY( a == -20 ); >>>>> } >>>>> >>>>> - VERIFY( value == 0x022 ); >>>>> + VERIFY( value == -20 ); >>>>> } >>>>> >>>>> void >>>>> @@ -292,9 +321,27 @@ test02() >>>>> v = a ^= 0x12; >>>>> VERIFY( v == 0x24 ); >>>>> VERIFY( a == 0x24 ); >>>>> + >>>>> + a = 100; >>>>> + v = a.fetch_min(50); >>>>> + VERIFY( v == 100 ); >>>>> + VERIFY( a == 50 ); >>>>> + >>>>> + v = a.fetch_min(75, mo); >>>>> + VERIFY( v == 50 ); >>>>> + VERIFY( a == 50 ); >>>>> + >>>>> + a = 20; >>>>> + v = a.fetch_max(50); >>>>> + VERIFY( v == 20 ); >>>>> + VERIFY( a == 50 ); >>>>> + >>>>> + v = a.fetch_max(30, mo); >>>>> + VERIFY( v == 50 ); >>>>> + VERIFY( a == 50 ); >>>>> } >>>>> >>>>> - VERIFY( value == 0x24 ); >>>>> + VERIFY( value == 50 ); >>>>> } >>>>> void >>>>> test03() >>>>> diff --git >>>>> a/libstdc++-v3/testsuite/29_atomics/headers/stdatomic.h/c_compat.cc >>>>> b/libstdc++-v3/testsuite/29_atomics/headers/stdatomic.h/c_compat.cc >>>>> index bcdb969b0c0..2e4c73c456c 100644 >>>>> --- a/libstdc++-v3/testsuite/29_atomics/headers/stdatomic.h/c_compat.cc >>>>> +++ b/libstdc++-v3/testsuite/29_atomics/headers/stdatomic.h/c_compat.cc >>>>> @@ -131,6 +131,10 @@ static_assert( requires (::atomic_int* i, int* e) { >>>>> ::atomic_fetch_or_explicit(i, 1, memory_order_relaxed); >>>>> ::atomic_fetch_xor(i, 1); >>>>> ::atomic_fetch_xor_explicit(i, 1, memory_order_relaxed); >>>>> + ::atomic_fetch_min(i, 1); >>>>> + ::atomic_fetch_min_explicit(i, 1, memory_order_relaxed); >>>>> + ::atomic_fetch_max(i, 1); >>>>> + ::atomic_fetch_max_explicit(i, 1, memory_order_relaxed); >>>>> } ); >>>>> >>>>> static_assert( requires (::atomic_flag* f) { >>>>> -- >>>>> 2.44.0 > > > <0001-libstdc-Implement-std-atomic-fetch_min-max.patch>
