Add build step for NVCC and fix a warning (#3227)

* 👷 add step for NVCC build #2676
* 🚨 fix warning (code taken from #2736)
* 👷 use version 2.2.0 of the CI image

.github/workflows/ubuntu.yml

@@ -11,7 +11,7 @@ on:
 jobs:
   ci_test_clang:
     runs-on: ubuntu-latest
-    container: ghcr.io/nlohmann/json-ci:v2.1.0
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
     steps:
       - uses: actions/checkout@v2
       - name: cmake
@@ -21,7 +21,7 @@ jobs:
 
   ci_test_gcc:
     runs-on: ubuntu-latest
-    container: ghcr.io/nlohmann/json-ci:v2.1.0
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
     steps:
       - uses: actions/checkout@v2
       - name: cmake
@@ -31,7 +31,7 @@ jobs:
 
   ci_static_analysis:
     runs-on: ubuntu-latest
-    container: ghcr.io/nlohmann/json-ci:v2.1.0
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
     strategy:
       matrix:
         target: [ci_clang_tidy, ci_cppcheck, ci_test_valgrind, ci_test_clang_sanitizer, ci_test_amalgamation, ci_clang_analyze, ci_cpplint, ci_cmake_flags, ci_single_binaries, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata, ci_infer]
@@ -44,7 +44,7 @@ jobs:
 
   ci_cmake_options:
     runs-on: ubuntu-latest
-    container: ghcr.io/nlohmann/json-ci:v2.1.0
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
     strategy:
       matrix:
         target: [ci_test_diagnostics, ci_test_noexceptions, ci_test_noimplicitconversions]
@@ -57,7 +57,7 @@ jobs:
 
   ci_test_coverage:
     runs-on: ubuntu-latest
-    container: ghcr.io/nlohmann/json-ci:v2.1.0
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
     steps:
       - uses: actions/checkout@v2
       - name: cmake
@@ -77,7 +77,7 @@ jobs:
 
   ci_test_compilers:
     runs-on: ubuntu-latest
-    container: ghcr.io/nlohmann/json-ci:v2.1.0
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
     strategy:
       matrix:
         compiler: [g++-4.8, g++-4.9, g++-5, g++-6, g++-7, g++-8, g++-9, g++-10, clang++-3.5, clang++-3.6, clang++-3.7, clang++-3.8, clang++-3.9, clang++-4.0, clang++-5.0, clang++-6.0, clang++-7, clang++-8, clang++-9, clang++-10, clang++-11, clang++-12, clang++-13]
@@ -90,7 +90,7 @@ jobs:
 
   ci_test_standards:
     runs-on: ubuntu-latest
-    container: ghcr.io/nlohmann/json-ci:v2.1.0
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
     strategy:
       matrix:
         standard: [11, 14, 17, 20]
@@ -101,3 +101,13 @@ jobs:
         run: cmake -S . -B build -DJSON_CI=On
       - name: build
         run: cmake --build build --target ci_test_${{ matrix.compiler }}_cxx${{ matrix.standard }}
+
+  ci_cuda_example:
+    runs-on: ubuntu-latest
+    container: ghcr.io/nlohmann/json-ci:v2.2.0
+    steps:
+      - uses: actions/checkout@v2
+      - name: cmake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: build
+        run: cmake --build build --target ci_cuda_example

cmake/ci.cmake

@@ -835,6 +835,18 @@ foreach(COMPILER g++-4.8 g++-4.9 g++-5 g++-6 g++-7 g++-8 g++-9 g++-10 clang++-3.
     unset(COMPILER_TOOL CACHE)
 endforeach()
 
+###############################################################################
+# CUDA example
+###############################################################################
+
+add_custom_target(ci_cuda_example
+    COMMAND ${CMAKE_COMMAND}
+        -DCMAKE_BUILD_TYPE=Debug -GNinja
+        -DCMAKE_CUDA_HOST_COMPILER=g++-8
+        -S${PROJECT_SOURCE_DIR}/test/cuda_example -B${PROJECT_BINARY_DIR}/build_cuda_example
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_cuda_example
+)
+
 ###############################################################################
 # Clean up all generated files.
 ###############################################################################

include/nlohmann/detail/output/serializer.hpp

@@ -664,6 +664,19 @@ class serializer
         }
     }
 
+    // templates to avoid warnings about useless casts
+    template <typename NumberType, enable_if_t<std::is_signed<NumberType>::value, int> = 0>
+    bool is_negative_number(NumberType x)
+    {
+        return x < 0;
+    }
+
+    template < typename NumberType, enable_if_t <std::is_unsigned<NumberType>::value, int > = 0 >
+    bool is_negative_number(NumberType /*unused*/)
+    {
+        return false;
+    }
+
     /*!
     @brief dump an integer
 
@@ -707,12 +720,11 @@ class serializer
         // use a pointer to fill the buffer
         auto buffer_ptr = number_buffer.begin(); // NOLINT(llvm-qualified-auto,readability-qualified-auto,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
 
-        const bool is_negative = std::is_signed<NumberType>::value && !(x >= 0); // see issue #755
         number_unsigned_t abs_value;
 
         unsigned int n_chars{};
 
-        if (is_negative)
+        if (is_negative_number(x))
         {
             *buffer_ptr = '-';
             abs_value = remove_sign(static_cast<number_integer_t>(x));

single_include/nlohmann/json.hpp

@@ -16707,6 +16707,19 @@ class serializer
         }
     }
 
+    // templates to avoid warnings about useless casts
+    template <typename NumberType, enable_if_t<std::is_signed<NumberType>::value, int> = 0>
+    bool is_negative_number(NumberType x)
+    {
+        return x < 0;
+    }
+
+    template < typename NumberType, enable_if_t <std::is_unsigned<NumberType>::value, int > = 0 >
+    bool is_negative_number(NumberType /*unused*/)
+    {
+        return false;
+    }
+
     /*!
     @brief dump an integer
 
@@ -16750,12 +16763,11 @@ class serializer
         // use a pointer to fill the buffer
         auto buffer_ptr = number_buffer.begin(); // NOLINT(llvm-qualified-auto,readability-qualified-auto,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
 
-        const bool is_negative = std::is_signed<NumberType>::value && !(x >= 0); // see issue #755
         number_unsigned_t abs_value;
 
         unsigned int n_chars{};
 
-        if (is_negative)
+        if (is_negative_number(x))
         {
             *buffer_ptr = '-';
             abs_value = remove_sign(static_cast<number_integer_t>(x));

test/cuda_example/CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.18)
+project(json_cuda LANGUAGES CUDA)
+
+add_executable(json_cuda json_cuda.cu)
+target_include_directories(json_cuda PRIVATE ../../include)
+target_compile_features(json_cuda PUBLIC cuda_std_11)
+set_target_properties(json_cuda PROPERTIES
+    CUDA_EXTENSIONS OFF
+    CUDA_STANDARD_REQUIRED ON
+)

test/cuda_example/json_cuda.cu

@@ -0,0 +1,7 @@
+#include <nlohmann/json.hpp>
+
+int main()
+{
+    nlohmann::ordered_json json = {"Test"};
+    json.dump();
+}