This branch improves portability (under Windows).

.github/workflows/alpine.yml

@@ -0,0 +1,27 @@
+name: Alpine Linux
+'on':
+  - push
+  - pull_request
+jobs:
+  ubuntu-build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: start docker
+        run: |
+          docker run -w /src -dit --name alpine -v $PWD:/src alpine:latest
+          echo 'docker exec alpine "$@";' > ./alpine.sh
+          chmod +x ./alpine.sh
+      - name: install packages
+        run: |
+          ./alpine.sh apk update
+          ./alpine.sh apk add build-base cmake g++ linux-headers git bash
+      - name: cmake
+        run: |
+          ./alpine.sh cmake -DFASTFLOAT_TEST=ON  -B build_for_alpine
+      - name: build
+        run: |
+          ./alpine.sh cmake --build build_for_alpine
+      - name: test
+        run: |
+          ./alpine.sh bash -c "cd build_for_alpine && ctest  -R basictest"

.github/workflows/msys2.yml

@@ -0,0 +1,44 @@
+name: MSYS2-CI
+
+on: [push, pull_request]
+
+jobs:
+  windows-mingw:
+    name: ${{ matrix.msystem }}
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - msystem: "MINGW64"
+            install: mingw-w64-x86_64-cmake mingw-w64-x86_64-ninja mingw-w64-x86_64-gcc
+            type: Release
+          - msystem: "MINGW32"
+            install: mingw-w64-i686-cmake mingw-w64-i686-ninja mingw-w64-i686-gcc
+            type: Release
+          - msystem: "MINGW64"
+            install: mingw-w64-x86_64-cmake mingw-w64-x86_64-ninja mingw-w64-x86_64-gcc
+            type: Debug
+          - msystem: "MINGW32"
+            install: mingw-w64-i686-cmake mingw-w64-i686-ninja mingw-w64-i686-gcc
+            type: Debug
+    env:
+      CMAKE_GENERATOR: Ninja
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: msys2/setup-msys2@v2
+        with:
+          update: true
+          msystem: ${{ matrix.msystem }}
+          install: ${{ matrix.install }}
+      - name: Build and Test
+        run: |
+          mkdir build
+          cd build
+          cmake -DCMAKE_BUILD_TYPE=${{ matrix.type }}  -DFASTFLOAT_TEST=ON ..
+          cmake --build . --verbose
+          ctest  --output-on-failure -R basictest

.github/workflows/vs16-clang-ci.yml

@@ -0,0 +1,25 @@
+ame: VS16-CLANG-CI
+
+on: [push, pull_request]
+
+jobs:
+  ci:
+    name: windows-vs16
+    runs-on: windows-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: 'Run CMake with VS16'
+      uses: lukka/run-cmake@v2
+      with:
+        cmakeListsOrSettingsJson: CMakeListsTxtAdvanced
+        cmakeListsTxtPath: '${{ github.workspace }}/CMakeLists.txt'
+        buildDirectory: "${{ github.workspace }}/../../_temp/windows"
+        cmakeBuildType: Release   
+        buildWithCMake: true
+        cmakeGenerator: VS16Win64 
+        cmakeAppendedArgs:  -T ClangCL -DFASTFLOAT_TEST=ON
+        buildWithCMakeArgs: --config Release  
+        
+    - name: 'Run CTest'
+      run: ctest -C Release -R basictest  --output-on-failure 
+      working-directory: "${{ github.workspace }}/../../_temp/windows"

include/fast_float/float_common.h

@@ -18,14 +18,17 @@
 #define fastfloat_really_inline inline __attribute__((always_inline))
 #endif 
 
-#ifdef _MSC_VER
-#define fastfloat_strcasecmp _stricmp
-#define fastfloat_strncasecmp _strnicmp
-#else
-#define fastfloat_strcasecmp strcasecmp
-#define fastfloat_strncasecmp strncasecmp
-#endif
 namespace fast_float {
+
+// Compares two ASCII strings in a case insensitive manner.
+inline bool fastfloat_strncasecmp(const char * input1, const char * input2, size_t length) {
+  char running_diff{0};
+  for(size_t i = 0; i < length; i++) {
+    running_diff |= (input1[i] ^ input2[i]);
+  }
+  return (running_diff == 0) || (running_diff == 32);
+}
+
 #ifndef FLT_EVAL_METHOD
 #error "FLT_EVAL_METHOD should be defined, please include cfloat."
 #endif
@@ -72,7 +75,8 @@ int leading_zeroes(uint64_t input_num) {
 }
 
 
-#ifdef FASTFLOAT_VISUAL_STUDIO
+#if defined(_WIN32) && !defined(__clang__)
+// Note MinGW falls here too
 #include <intrin.h>
 
 #if !defined(_M_X64) && !defined(_M_ARM64)// _umul128 for x86, arm