Ensure compilation with C++11

cub/test/test_device_histogram.cu

@@ -82,7 +82,7 @@ auto castIfArrayOfHalfPointers(T** p) -> T**
 }
 
 #if TEST_HALF_T
-auto castIfHalfPointer(half_t* p)
+auto castIfHalfPointer(half_t* p) -> __half*
 {
   return reinterpret_cast<__half*>(p);
 }
@@ -290,8 +290,8 @@ auto GenerateSample(LevelT max_level, int entropy_reduction) -> T
   unsigned int bits;
   RandomBits(bits, entropy_reduction);
   const auto max = std::numeric_limits<unsigned int>::max();
-  return static_cast<T>((static_cast<float>(bits) / max) * max_level); // TODO(bgruber): this could use a better
-                                                                       // generator
+  return static_cast<T>(static_cast<float>(bits) / static_cast<float>(max) * max_level); // TODO(bgruber): this could
+                                                                                         // use a better generator
 }
 
 template <int NUM_CHANNELS, int NUM_ACTIVE_CHANNELS, typename LevelT, typename SampleT, typename OffsetT>
@@ -470,7 +470,7 @@ void TestHistogramEven(
     _CCCL_IF_CONSTEXPR (!std::is_integral<LevelT>::value)
     {
       fpScales[channel] =
-        LevelT{1.0f}
+        LevelT{1}
         / static_cast<LevelT>(
           (upper_level[channel] - lower_level[channel]) / static_cast<LevelT>(num_levels[channel] - 1));
     }
@@ -1143,7 +1143,10 @@ void TestChannels(LevelT max_level, int max_num_levels)
 {
   // TODO(bgruber): replace TestChannelsImpl with if constexpr in C++17
   TestChannelsImpl<SampleT, CounterT, LevelT, OffsetT>(
-    max_level, max_num_levels, std::bool_constant<TestExtraChannels>{}, std::bool_constant<ActuallyRun>{});
+    max_level,
+    max_num_levels,
+    std::integral_constant<bool, TestExtraChannels>{},
+    std::integral_constant<bool, ActuallyRun>{}); // TODO(bgruber): use std::bool_constant with C++17
 }
 
 void TestLevelsAliasing()
@@ -1161,7 +1164,8 @@ void TestLevelsAliasing()
     11, 11, 11, 11, 11, 11 // bin 5
   };
 
-  constexpr int num_samples = std::size(h_samples);
+  constexpr int num_samples = sizeof(h_samples) / sizeof(h_samples[0]); // TODO(bgruber) use std::size(h_samples) in
+                                                                        // C++17
 
   int* d_histogram = nullptr;
   int* d_samples   = nullptr;
@@ -1206,7 +1210,8 @@ void TestIntegerBinCalcs()
   constexpr int lower_level = 0;
   constexpr int upper_level = 12;
 
-  constexpr int num_samples = std::size(h_samples);
+  constexpr int num_samples = sizeof(h_samples) / sizeof(h_samples[0]); // TODO(bgruber) use std::size(h_samples) in
+                                                                        // C++17
 
   int* d_histogram = nullptr;
   int* d_samples   = nullptr;