Merge 78b6a96f28b9a7b66a4d95a34fb3ed9edbb73163 into 33785d5d61993b8c22eacc58108e1cf109eca490

.github/workflows/ubuntu22-clang.yml

@@ -9,6 +9,14 @@ jobs:
       - uses: actions/checkout@v7
       - name: Install clang++-14
         run: sudo apt-get install -y clang++-14
+      - name: Check for pedantic warnings in pre-C++20 modes (issue 427)
+        run: |
+          set -xe
+          printf '#include "fast_float/fast_float.h"\nint main() { return 0; }\n' > pedantic_check.cpp
+          for std in c++11 c++14 c++17 c++20; do
+            clang++-14 -std=$std -Wall -Wextra -pedantic-errors -Werror \
+              -Iinclude -fsyntax-only pedantic_check.cpp
+          done
       - name: Use cmake
         run: |
           mkdir build &&
@@ -22,4 +30,4 @@ jobs:
           cd build20 &&
           CXX=clang++-14 cmake -DFASTFLOAT_CONSTEXPR_TESTS=ON -DFASTFLOAT_CXX_STANDARD=20 -DFASTFLOAT_TEST=ON  ..  &&
           cmake --build .   &&
-          ctest --output-on-failure
+          ctest --output-on-failure

include/fast_float/ascii_number.h

@@ -622,10 +622,22 @@ parse_number_string(UC const *p, UC const *pend, parse_options_t<UC> options,
   // JSON and JavaScript are mutually exclusive, so only the non-JSON
   // instantiation has to look at the flag.
   FASTFLOAT_IF_CONSTEXPR17(!basic_json_fmt) {
+    // We have to disable -Wc++20-extensions for the [[unlikely]] attribute
+    // See comment for @jwakely at
+    // https://github.com/fastfloat/fast_float/pull/387#discussion_r3366943539
+#ifdef __clang__
+#pragma clang diagnostic push
+#if (!defined(__APPLE_CC__) && __clang_major__ >= 10) || (__clang_major__ >= 13)
+#pragma clang diagnostic ignored "-Wc++20-extensions"
+#endif
+#endif
     if fastfloat_unlikely (uint64_t(options.format &
                                     detail::basic_javascript_fmt)) {
       return parse_number_string_javascript<UC>(p, pend, options, store_spans);
     }
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
   }
   return parse_number_string_impl<basic_json_fmt, false, UC>(p, pend, options,
                                                              store_spans);

include/fast_float/parse_number.h

@@ -391,9 +391,19 @@ from_chars_float_advanced(UC const *first, UC const *last, T &value,
   // Leave for the javascript conversion before anything else is live, so this
   // compiles to a tail call and the common path keeps its registers. The cold
   // function repeats the leading-whitespace and empty-input handling below.
+  // See the comment on -Wc++20-extensions further down in this function.
+#ifdef __clang__
+#pragma clang diagnostic push
+#if (!defined(__APPLE_CC__) && __clang_major__ >= 10) || (__clang_major__ >= 13)
+#pragma clang diagnostic ignored "-Wc++20-extensions"
+#endif
+#endif
   if fastfloat_unlikely (uint64_t(fmt & detail::basic_javascript_fmt)) {
     return from_chars_float_javascript<T, UC>(first, last, value, options);
   }
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
 
   from_chars_result_t<UC> answer;
   if (uint64_t(fmt & chars_format::skip_white_space)) {