Fix nightly GCC8 build regressions in bit_cast and DeviceReduce

ci/util/build_and_test_targets.sh

@@ -73,7 +73,7 @@ if [[ -n "${CONFIGURE_OVERRIDE}" ]]; then
   if [[ -n "${PRESET}" ]]; then
     echo "::warning:: --preset ignored due to --configure-override" >&2
   fi
-  if [[ "${#CMAKE_OPTIONS}" -gt 0 ]]; then
+  if [[ "${#CMAKE_OPTIONS[@]}" -gt 0 ]]; then
     echo "::warning:: --cmake-options ignored due to --configure-override" >&2
   fi
 fi
@@ -103,15 +103,15 @@ if [[ -z "${BUILD_DIR}" ]]; then
   exit 1
 fi
 
-if [[ "${#BUILD_TARGETS}" -gt 0 ]]; then
+if [[ "${#BUILD_TARGETS[@]}" -gt 0 ]]; then
   if ! (set -x; ninja -C "${BUILD_DIR}" "${BUILD_TARGETS[@]}"); then
     echo "::endgroup::"
     echo "🔴🛠️ Ninja build failed for targets ($(elapsed_time)): ${BUILD_TARGETS[*]@Q}"
     exit 1
   fi
 fi
 
-if [[ "${#CTEST_TARGETS}" -gt 0 ]]; then
+if [[ "${#CTEST_TARGETS[@]}" -gt 0 ]]; then
   for t in "${CTEST_TARGETS[@]}"; do
     if ! (set -x; ctest --test-dir "${BUILD_DIR}" -R "$t" -V --output-on-failure); then
       echo "::endgroup::"
@@ -121,7 +121,7 @@ if [[ "${#CTEST_TARGETS}" -gt 0 ]]; then
   done
 fi
 
-if [[ "${#LIT_PRECOMPILE_TESTS}" -gt 0 || "${#LIT_TESTS}" -gt 0 ]]; then
+if [[ "${#LIT_PRECOMPILE_TESTS[@]}" -gt 0 || "${#LIT_TESTS[@]}" -gt 0 ]]; then
   lit_site_cfg="${BUILD_DIR}/libcudacxx/test/libcudacxx/lit.site.cfg"
   if [[ ! -f "${lit_site_cfg}" ]]; then
     echo "::endgroup::"
@@ -130,7 +130,7 @@ if [[ "${#LIT_PRECOMPILE_TESTS}" -gt 0 || "${#LIT_TESTS}" -gt 0 ]]; then
   fi
 fi
 
-if [[ "${#LIT_PRECOMPILE_TESTS}" -gt 0 ]]; then
+if [[ "${#LIT_PRECOMPILE_TESTS[@]}" -gt 0 ]]; then
   for t in "${LIT_PRECOMPILE_TESTS[@]}"; do
     t_path="libcudacxx/test/libcudacxx/${t}"
     if ! (set -x; LIBCUDACXX_SITE_CONFIG="${lit_site_cfg}" lit -v "-Dexecutor=NoopExecutor()" "${t_path}"); then
@@ -141,7 +141,7 @@ if [[ "${#LIT_PRECOMPILE_TESTS}" -gt 0 ]]; then
   done
 fi
 
-if [[ "${#LIT_TESTS}" -gt 0 ]]; then
+if [[ "${#LIT_TESTS[@]}" -gt 0 ]]; then
   for t in "${LIT_TESTS[@]}"; do
     t_path="libcudacxx/test/libcudacxx/${t}"
     if ! (set -x; LIBCUDACXX_SITE_CONFIG="${lit_site_cfg}" lit -v "${t_path}"); then

cub/cub/device/device_reduce.cuh

@@ -116,6 +116,8 @@ private:
 
       if constexpr (Determinism == ::cuda::execution::determinism::__determinism_t::__gpu_to_gpu)
       {
+        // Only instantiated with `plus<float|double>`; RFA hardcodes `deterministic_sum_t<accum_t>`.
+        (void) reduction_op;
         using default_policy_selector = detail::rfa::policy_selector_from_types<accum_t>;
         using policy_selector =
           ::cuda::std::execution::__query_result_or_t<tuning_env_t, detail::rfa::rfa_policy, default_policy_selector>;

libcudacxx/include/cuda/std/__algorithm/copy.h

@@ -86,13 +86,11 @@ _CCCL_EXEC_CHECK_DISABLE
 template <class _Tp, class _Up>
 _CCCL_API constexpr bool __constexpr_tail_overlap(_Tp* __first, _Up* __needle, [[maybe_unused]] _Tp* __last)
 {
-#if !_CCCL_TILE_COMPILATION() // pointer values cannot be compared
-  if (!::cuda::std::is_constant_evaluated())
+  if (!::cuda::std::__cccl_default_is_constant_evaluated())
   {
     return __first < __needle;
   }
   else
-#endif // !_CCCL_TILE_COMPILATION()
   {
 #if defined(_CCCL_BUILTIN_CONSTANT_P)
     NV_IF_ELSE_TARGET(NV_IS_HOST,

libcudacxx/include/cuda/std/__bit/bit_cast.h

@@ -51,10 +51,10 @@ _CCCL_DIAG_SUPPRESS_GCC("-Wclass-memaccess")
 template <class _To, class _From>
 [[nodiscard]] _CCCL_API inline _To __bit_cast_memcpy(const _From& __from) noexcept
 {
-#if !_CCCL_COMPILER(GCC, <=, 7)
+#if !_CCCL_COMPILER(GCC, <=, 8)
   static_assert(::cuda::std::default_initializable<_To>,
-                "bit_cast memcpy fallback requires the destination type to be default initializable");
-#endif // !_CCCL_COMPILER(GCC, <=, 7)
+                "bit_cast memcpy fallback requires the destination type to be default constructible");
+#endif // !_CCCL_COMPILER(GCC, <=, 8)
   _To __temp;
   ::cuda::std::memcpy(&__temp, &__from, sizeof(_To));
   return __temp;

libcudacxx/test/libcudacxx/std/numerics/simd/simd.mask.class/ctor.pass.cpp

@@ -123,7 +123,7 @@ template <int Bytes, int N>
 TEST_FUNC constexpr void test_generator()
 {
   using Mask = simd::basic_mask<Bytes, simd::fixed_size<N>>;
-#if _CCCL_COMPILER(GCC, !=, 7)
+#if _CCCL_COMPILER(GCC, >=, 9)
   static_assert(!noexcept(Mask(is_even{})));
 #endif