Improve std::plus void detection

CMakeLists.txt

@@ -460,17 +460,6 @@ else()
     endif()
 endif()
 
-# Availability of std::plus without class specifier
-if(CMAKE_CXX_STANDARD VERSION_GREATER 11)
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-        if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 5.4.0)
-            set(HAVE_STD_PLUS ON)
-        endif()
-    else()
-        set(HAVE_STD_PLUS ON)
-    endif()
-endif()
-
 
 
 ################################################################################
@@ -901,6 +890,22 @@ check_cxx_source_compiles("
 
 
 
+################################################################################
+# Detect availability of std::plus without class specifier
+################################################################################
+unset(has_std_plus_void CACHE)
+if(CMAKE_CXX_STANDARD VERSION_GREATER 11)
+    include(CheckCXXSourceCompiles)
+    check_cxx_source_compiles("
+        #include <functional>
+        int main()
+        { [](float a=1, float b=0){return std::plus<>();}; };"
+        has_std_plus_void
+    )
+endif()
+
+
+
 ################################################################################
 # VOLK - Vector-Optimized Library of Kernels
 ################################################################################

src/tests/CMakeLists.txt

@@ -238,8 +238,8 @@ if(ARMADILLO_VERSION_STRING VERSION_GREATER 8.400)
     add_definitions(-DARMADILLO_HAVE_MVNRND=1)
 endif()
 
-if(HAVE_STD_PLUS)
+if(has_std_plus_void)
-    add_definitions(-DCOMPILER_HAS_STD_PLUS=1)
+    add_definitions(-DCOMPILER_HAS_STD_PLUS_VOID=1)
 endif()
 
 find_package(Gnuplot)

src/tests/benchmarks/CMakeLists.txt

@@ -107,6 +107,6 @@ add_benchmark(benchmark_preamble core_system_parameters)
 add_benchmark(benchmark_detector core_system_parameters)
 
 
-if(HAVE_STD_PLUS)
+if(has_std_plus_void)
-    target_compile_definitions(benchmark_detector PRIVATE -DCOMPILER_HAS_STD_PLUS=1)
+    target_compile_definitions(benchmark_detector PRIVATE -DCOMPILER_HAS_STD_PLUS_VOID=1)
 endif()

src/tests/benchmarks/benchmark_detector.cc

@@ -83,7 +83,7 @@ void bm_accumulate(benchmark::State& state)
         }
 }
 
-#if COMPILER_HAS_STD_PLUS
+
 void bm_inner_product(benchmark::State& state)
 {
     std::vector<float> d_symbol_history(GPS_CA_PREAMBLE_LENGTH_SYMBOLS, 0.0);
@@ -104,15 +104,16 @@ void bm_inner_product(benchmark::State& state)
                 d_symbol_history.end(),
                 d_preamble_samples.begin(),
                 0,
+#if COMPILER_HAS_STD_PLUS_VOID
                 std::plus<>(),
+#else
+                std::plus<float>(),
+#endif
                 [&](float a, float b) { return (std::signbit(a) ? -b : b); });
         }
 }
-#endif
 
 BENCHMARK(bm_forloop);
 BENCHMARK(bm_accumulate);
-#if COMPILER_HAS_STD_PLUS
 BENCHMARK(bm_inner_product);
-#endif
 BENCHMARK_MAIN();

src/tests/unit-tests/arithmetic/preamble_correlator_test.cc

@@ -84,7 +84,6 @@ TEST(PreambleCorrelationTest, TestMethods)
         }
     end2 = std::chrono::system_clock::now();
 
-#if COMPILER_HAS_STD_PLUS
     // Compute correlation, method 3
     start3 = std::chrono::system_clock::now();
     for (int64_t iter = 0; iter < n_iter; iter++)
@@ -93,25 +92,25 @@ TEST(PreambleCorrelationTest, TestMethods)
                 d_symbol_history.begin() + GPS_CA_PREAMBLE_LENGTH_BITS,
                 d_preamble_samples.begin(),
                 0,
+#if COMPILER_HAS_STD_PLUS_VOID
                 std::plus<>(),
-                [&](float a, float b) { return (std::signbit(a) ? -b : b); });
+#else
+                std::plus<float>(),
+#endif
             sum_corr3 += corr_value3;
         }
     end3 = std::chrono::system_clock::now();
-    std::chrono::duration<double> elapsed_seconds3 = end3 - start3;
-    EXPECT_EQ(corr_value, corr_value3);
-    EXPECT_EQ(sum_corr1, sum_corr3);
-#endif
-
-    EXPECT_EQ(corr_value, corr_value2);
-    EXPECT_EQ(sum_corr1, sum_corr2);
 
     std::chrono::duration<double> elapsed_seconds = end - start;
     std::chrono::duration<double> elapsed_seconds2 = end2 - start2;
+    std::chrono::duration<double> elapsed_seconds3 = end3 - start3;
+
+    EXPECT_EQ(corr_value, corr_value2);
+    EXPECT_EQ(sum_corr1, sum_corr2);
+    EXPECT_EQ(corr_value, corr_value3);
+    EXPECT_EQ(sum_corr1, sum_corr3);
 
     std::cout << "Correlation computed with 'C for'       : done in " << elapsed_seconds.count() * 1.0e9 / n_iter << " nanoseconds" << std::endl;
     std::cout << "Correlation computed with accumulate    : done in " << elapsed_seconds2.count() * 1.0e9 / n_iter << " nanoseconds" << std::endl;
-#if COMPILER_HAS_STD_PLUS
     std::cout << "Correlation computed with inner_product : done in " << elapsed_seconds3.count() * 1.0e9 / n_iter << " nanoseconds" << std::endl;
-#endif
 }