Merge branch 'develop' into claude/pr-3899-merge-requirements-e1932e

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/docset/docSet.sql

@@ -16,6 +16,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('basic_json', 'Class', 'api/ba
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::accept', 'Function', 'api/basic_json/accept/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::array', 'Function', 'api/basic_json/array/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::array_t', 'Type', 'api/basic_json/array_t/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::as_base_class', 'Method', 'api/basic_json/as_base_class/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::at', 'Method', 'api/basic_json/at/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::back', 'Method', 'api/basic_json/back/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::basic_json', 'Constructor', 'api/basic_json/basic_json/index.html');

docs/mkdocs/docs/api/basic_json/as_base_class.md

@@ -0,0 +1,53 @@
+# <small>nlohmann::basic_json::</small>as_base_class
+
+```cpp
+json_base_class_t& as_base_class() noexcept;
+const json_base_class_t& as_base_class() const noexcept;
+```
+
+Returns a reference to this object as its custom base class [`json_base_class_t`](json_base_class_t.md). No copy is
+made.
+
+Since `basic_json` derives from `json_base_class_t`, a member of `basic_json` hides any member of the custom base class
+with the same name. This function makes such hidden members accessible again.
+
+## Return value
+
+reference to this object as [`json_base_class_t`](json_base_class_t.md)
+
+## Exception safety
+
+No-throw guarantee: this function never throws exceptions.
+
+## Complexity
+
+Constant.
+
+## Notes
+
+The function is equivalent to `static_cast<json_base_class_t&>(j)` (or `static_cast<const json_base_class_t&>(j)`).
+
+## Examples
+
+??? example
+
+    The example shows how to use `as_base_class` to access members of the custom base class that are hidden by members
+    of `basic_json`.
+    
+    ```cpp
+    --8<-- "examples/as_base_class.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/as_base_class.output"
+    ```
+
+## See also
+
+- [json_base_class_t](json_base_class_t.md) - type of the custom base class
+
+## Version history
+
+- Added in version 3.13.0.

docs/mkdocs/docs/api/basic_json/index.md

@@ -200,6 +200,7 @@ Direct access to the stored value of a JSON value.
 - [**get_ref**](get_ref.md) - get a reference value
 - [**operator ValueType**](operator_ValueType.md) - get a value
 - [**get_binary**](get_binary.md) - get a binary value
+- [**as_base_class**](as_base_class.md) - access the custom base class
 
 ### Element access
 

docs/mkdocs/docs/api/basic_json/json_base_class_t.md

@@ -27,6 +27,18 @@ A `CustomBaseClass` with non-static data members forfeits `basic_json`'s
 [standard layout](https://en.cppreference.com/w/cpp/named_req/StandardLayoutType) guarantee. See
 [Template Parameter Requirements](../../features/types/template_parameters.md#custombaseclass).
 
+#### Name conflicts
+
+Since `basic_json` derives from `CustomBaseClass`, members of `basic_json` hide members of `CustomBaseClass` with the
+same name. Hidden members remain accessible via [`as_base_class`](as_base_class.md) or by casting the value to
+`json_base_class_t`.
+
+!!! warning "Avoid generic member names"
+
+    Future versions of the library may add members to `basic_json` that hide members of `CustomBaseClass` that are
+    accessible today. To reduce the risk of such conflicts, avoid generic names for the members of `CustomBaseClass`,
+    for instance by using a distinctive prefix.
+
 ## Examples
 
 ??? example
@@ -43,6 +55,11 @@ A `CustomBaseClass` with non-static data members forfeits `basic_json`'s
     --8<-- "examples/json_base_class_t.output"
     ```
 
+## See also
+
+- [as_base_class](as_base_class.md) - access the custom base class
+
 ## Version history
 
 - Added in version 3.12.0.
+- Made a public member type in version 3.13.0; it was private before, so it could not be named outside the class.

docs/mkdocs/docs/examples/as_base_class.cpp

@@ -0,0 +1,41 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+class base_class_with_hidden_members
+{
+  public:
+    const char* type_name() const noexcept
+    {
+        return "my_type_name";
+    }
+
+    std::size_t size() const noexcept
+    {
+        return 42;
+    }
+};
+
+using json = nlohmann::basic_json <
+             std::map,
+             std::vector,
+             std::string,
+             bool,
+             std::int64_t,
+             std::uint64_t,
+             double,
+             std::allocator,
+             nlohmann::adl_serializer,
+             std::vector<std::uint8_t>,
+             base_class_with_hidden_members
+             >;
+
+int main()
+{
+    json j = {1, 2, 3};
+
+    // the members of basic_json hide the members of the base class
+    std::cout << j.type_name() << ' ' << j.size() << '\n';
+
+    // access the hidden members of the base class
+    std::cout << j.as_base_class().type_name() << ' ' << j.as_base_class().size() << '\n';
+}

docs/mkdocs/docs/examples/as_base_class.output

@@ -0,0 +1,2 @@
+array 3
+my_type_name 42

docs/mkdocs/mkdocs.yml

@@ -114,6 +114,7 @@ nav:
           - 'accept': api/basic_json/accept.md
           - 'array': api/basic_json/array.md
           - 'array_t': api/basic_json/array_t.md
+          - 'as_base_class': api/basic_json/as_base_class.md
           - 'at': api/basic_json/at.md
           - 'back': api/basic_json/back.md
           - 'begin': api/basic_json/begin.md

include/nlohmann/detail/input/lexer.hpp

@@ -9,8 +9,10 @@
 #pragma once
 
 #include <array> // array
+#include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdio> // snprintf
+#include <cstdlib> // strtof, strtod, strtold, strtoll, strtoull
 #include <initializer_list> // initializer_list
 #include <string> // char_traits, string
 #include <utility> // move
@@ -215,6 +217,18 @@ class lexer : public lexer_base<BasicJsonType>
     ~lexer() = default;
 
   private:
+    /////////////////////
+    // locales
+    /////////////////////
+
+    /// return the decimal point of the current locale
+    static char get_decimal_point() noexcept
+    {
+        const auto* loc = localeconv();
+        JSON_ASSERT(loc != nullptr);
+        return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point);
+    }
+
     /////////////////////
     // scan functions
     /////////////////////
@@ -1022,6 +1036,24 @@ class lexer : public lexer_base<BasicJsonType>
         }
     }
 
+    JSON_HEDLEY_NON_NULL(2)
+    static void strtof(float& f, const char* str, char** endptr) noexcept
+    {
+        f = std::strtof(str, endptr);
+    }
+
+    JSON_HEDLEY_NON_NULL(2)
+    static void strtof(double& f, const char* str, char** endptr) noexcept
+    {
+        f = std::strtod(str, endptr);
+    }
+
+    JSON_HEDLEY_NON_NULL(2)
+    static void strtof(long double& f, const char* str, char** endptr) noexcept
+    {
+        f = std::strtold(str, endptr);
+    }
+
     /*!
     @brief scan a number literal
 
@@ -1061,7 +1093,7 @@ class lexer : public lexer_base<BasicJsonType>
     @note The scanner is independent of the current locale: token_buffer
           always holds `.`. Only the std::strtod fallback of convert_number()
           depends on the locale, and it looks up the decimal point right
-          before converting (see detail::convert_float_locale_aware()).
+          before converting (see convert_float_locale_aware()).
     */
     token_type scan_number()  // lgtm [cpp/use-of-goto] `goto` is used in this function to implement the number-parsing state machine described above. By design, any finite input will eventually reach the "done" state or return token_type::parse_error. In each intermediate state, 1 byte of the input is appended to the token_buffer vector, and only the already initialized variables token_buffer, number_type, and error_message are manipulated.
     {
@@ -1392,6 +1424,59 @@ scan_number_done:
         return token_type::uninitialized;
     }
 
+    /*!
+    @brief check whether Clinger's fast path can still succeed for this token
+
+    parse_float_fast() needs a significand below 2^53. A mantissa with 17 or
+    more significant digits is at least 10^16 and therefore always exceeds it,
+    so calling the fast path would walk the token one extra time only to
+    decline before strtod has to run anyway.
+
+    Significant digits are the mantissa's digits from the first nonzero one on;
+    the sign, the decimal point, leading zeros, and the exponent do not count.
+    The answer is derived from indices - the digits are not scanned again - so
+    this stays off the hot path of the number scanners.
+
+    @param[in] mantissa_end  offset just past the last mantissa byte in
+                             token_buffer
+    @return false if parse_float_fast() is guaranteed to decline
+    */
+    bool mantissa_fits_clinger(std::size_t mantissa_end) const
+    {
+        // 10^16 already exceeds 2^53, so 17 digits can never fit
+        constexpr std::size_t limit = 17;
+
+        const std::size_t neg = (!token_buffer.empty() && token_buffer[0] == '-') ? 1u : 0u;
+        const std::size_t has_dot = (decimal_point_position != std::string::npos) ? 1u : 0u;
+        // the JSON grammar restricts the integer part to "0" or [1-9][0-9]*, so
+        // a leading zero can only be a lone "0", which is not significant
+        const std::size_t lead_zero = (token_buffer[neg] == '0') ? 1u : 0u;
+        JSON_ASSERT(mantissa_end >= neg + has_dot + lead_zero);
+        std::size_t digits = mantissa_end - neg - has_dot - lead_zero;
+
+        if (JSON_HEDLEY_LIKELY(digits < limit))
+        {
+            return true;
+        }
+
+        // Only a number below 1 can carry further insignificant zeros, and only
+        // while the count stays at the limit does removing them change the
+        // answer - so this loop is skipped for all but a few tokens. The
+        // fraction is located through decimal_point_position rather than by
+        // searching '.'.
+        if (lead_zero != 0)
+        {
+            JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
+            for (std::size_t i = decimal_point_position + 1;
+                    digits >= limit && i < mantissa_end && token_buffer[i] == '0'; ++i)
+            {
+                --digits;
+            }
+        }
+
+        return digits < limit;
+    }
+
     /*!
     @brief convert the number text in token_buffer to its value and token type
 
@@ -1405,7 +1490,7 @@ scan_number_done:
                              token_buffer (the index of 'e'/'E', or
                              token_buffer.size() when there is no exponent);
                              used to skip Clinger's fast path when it cannot
-                             possibly succeed - see detail::mantissa_fits_clinger()
+                             possibly succeed - see mantissa_fits_clinger()
     */
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
@@ -1478,15 +1563,77 @@ scan_number_done:
         // (Eisel-Lemire, locale-independent, correctly rounded) when available;
         // otherwise the exact Clinger fast path (double only); otherwise the
         // locale-aware strtof/strtod/strtold.
-        if (convert_float_fast(num_begin, num_end, decimal_point_position, mantissa_end, value_float))
+        if (parse_float_from_chars(num_begin, num_end, value_float))
+        {
+            return token_type::value_float;
+        }
+        // Skipping a fast path that cannot succeed is lossless and saves a full
+        // extra pass over the token's bytes, which otherwise shows up on
+        // high-precision inputs such as canada.json
+        if (mantissa_fits_clinger(mantissa_end)
+                && parse_float_fast(num_begin, num_end, value_float))
         {
             return token_type::value_float;
         }
 
-        convert_float_locale_aware(token_buffer, decimal_point_position, value_float);
+        convert_float_locale_aware();
         return token_type::value_float;
     }
 
+    /*!
+    @brief convert the float in token_buffer with strtof/strtod/strtold
+
+    These functions expect the decimal point of the *current* locale, so it is
+    looked up right before the conversion instead of once when the lexer is
+    constructed: a locale change in between (by a parser callback, a SAX
+    handler, or another thread) must not truncate the value (#5198). The
+    token has been validated before, so if the conversion stops early and the
+    decimal point changed in the meantime, the locale changed between the
+    lookup and the call, and the conversion is repeated with the new decimal
+    point. If the decimal point did not change, a retry cannot succeed: the
+    locale's decimal point is not a single character (e.g., the two-byte
+    U+066B of ar_EG.UTF-8 or fa_IR.UTF-8) and cannot be substituted in place.
+    The value strtod parsed up to that point is kept, as before this change.
+
+    Note that changing the locale in another thread *while* strtod runs is
+    undefined behavior of the C library, which this function cannot prevent.
+    */
+    void convert_float_locale_aware()
+    {
+        const bool has_dot = decimal_point_position != std::string::npos;
+        char decimal_point = get_decimal_point();
+        for (;;)
+        {
+            const bool substitute = has_dot && decimal_point != '.';
+            if (substitute)
+            {
+                token_buffer[decimal_point_position] = static_cast<typename string_t::value_type>(decimal_point);
+            }
+
+            char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+            strtof(value_float, token_buffer.data(), &endptr);
+
+            if (substitute)
+            {
+                // get_string() hands the token to the SAX interface with '.'
+                token_buffer[decimal_point_position] = '.';
+            }
+
+            if (JSON_HEDLEY_LIKELY(endptr == token_buffer.data() + token_buffer.size()))
+            {
+                return;
+            }
+
+            // retry only if the locale changed; otherwise, this would loop forever
+            const char current_decimal_point = get_decimal_point();
+            if (current_decimal_point == decimal_point)
+            {
+                return;
+            }
+            decimal_point = current_decimal_point;
+        }
+    }
+
     /*!
     @brief contiguous fast path for scanning a number
 

include/nlohmann/detail/input/number_parse.hpp

@@ -10,12 +10,9 @@
 
 #include <array> // array
 #include <cfloat> // FLT_EVAL_METHOD
-#include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdint> // int64_t, uint64_t
-#include <cstdlib> // strtof, strtod, strtold
 #include <limits> // numeric_limits
-#include <string> // string
 
 #include <nlohmann/detail/macro_scope.hpp>
 
@@ -32,9 +29,8 @@
 
 // This file contains the value-conversion helpers used by the lexer to turn an
 // already-validated number token into a value, without the locale/errno
-// overhead of std::strtoull/std::strtod where possible. They are free functions
-// so the lexer stays focused on scanning (see lexer::convert_number()) and so
-// that other parsers of JSON text can convert tokens exactly like it does.
+// overhead of std::strtoull/std::strtod. They are free functions so the lexer
+// stays focused on scanning; see lexer::convert_number().
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -297,183 +293,5 @@ bool parse_float_from_chars(const char* first, const char* last, FloatType& out)
 #endif
 }
 
-/*!
-@brief check whether Clinger's fast path can still succeed for a float token
-
-parse_float_fast() needs a significand below 2^53. A mantissa with 17 or
-more significant digits is at least 10^16 and therefore always exceeds it,
-so calling the fast path would walk the token one extra time only to
-decline before strtod has to run anyway.
-
-Significant digits are the mantissa's digits from the first nonzero one on;
-the sign, the decimal point, leading zeros, and the exponent do not count.
-The answer is derived from indices - the digits are not scanned again - so
-this stays off the hot path of the number scanners.
-
-@param[in] token                   the validated number token ('.' as decimal point)
-@param[in] decimal_point_position  index of the '.' in @a token, or
-                                   std::string::npos if there is none
-@param[in] mantissa_end            offset just past the last mantissa byte
-@return false if parse_float_fast() is guaranteed to decline
-*/
-inline bool mantissa_fits_clinger(const char* token, std::size_t decimal_point_position, std::size_t mantissa_end) noexcept
-{
-    // 10^16 already exceeds 2^53, so 17 digits can never fit
-    constexpr std::size_t limit = 17;
-
-    const std::size_t neg = (token[0] == '-') ? 1u : 0u;
-    const std::size_t has_dot = (decimal_point_position != std::string::npos) ? 1u : 0u;
-    // the JSON grammar restricts the integer part to "0" or [1-9][0-9]*, so
-    // a leading zero can only be a lone "0", which is not significant
-    const std::size_t lead_zero = (token[neg] == '0') ? 1u : 0u;
-    JSON_ASSERT(mantissa_end >= neg + has_dot + lead_zero);
-    std::size_t digits = mantissa_end - neg - has_dot - lead_zero;
-
-    if (JSON_HEDLEY_LIKELY(digits < limit))
-    {
-        return true;
-    }
-
-    // Only a number below 1 can carry further insignificant zeros, and only
-    // while the count stays at the limit does removing them change the
-    // answer - so this loop is skipped for all but a few tokens. The
-    // fraction is located through decimal_point_position rather than by
-    // searching '.'.
-    if (lead_zero != 0)
-    {
-        JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
-        for (std::size_t i = decimal_point_position + 1;
-                digits >= limit && i < mantissa_end && token[i] == '0'; ++i)
-        {
-            --digits;
-        }
-    }
-
-    return digits < limit;
-}
-
-/*!
-@brief convert a validated float token without the C library, if possible
-
-Tries std::from_chars (when available) and then Clinger's exact fast path
-(double only), skipping the latter when it cannot succeed.
-
-@param[in]  first                   pointer to the first character of the token
-@param[in]  last                    pointer past the last character
-@param[in]  decimal_point_position  index of the '.' in the token, or
-                                    std::string::npos if there is none
-@param[in]  mantissa_end            offset just past the last mantissa byte (the
-                                    index of 'e'/'E', or the token length)
-@param[out] value                   the converted value on success
-@return true if the value was converted; false if convert_float_locale_aware()
-        must convert it
-*/
-template<typename FloatType>
-bool convert_float_fast(const char* first, const char* last, std::size_t decimal_point_position,
-                        std::size_t mantissa_end, FloatType& value) noexcept
-{
-    if (parse_float_from_chars(first, last, value))
-    {
-        return true;
-    }
-    // Skipping a fast path that cannot succeed is lossless and saves a full
-    // extra pass over the token's bytes, which otherwise shows up on
-    // high-precision inputs such as canada.json
-    return mantissa_fits_clinger(first, decimal_point_position, mantissa_end)
-           && parse_float_fast(first, last, value);
-}
-
-/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
-JSON_HEDLEY_NON_NULL(2)
-inline void strtof_by_type(float& f, const char* str, char** endptr) noexcept
-{
-    f = std::strtof(str, endptr);
-}
-
-/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
-JSON_HEDLEY_NON_NULL(2)
-inline void strtof_by_type(double& f, const char* str, char** endptr) noexcept
-{
-    f = std::strtod(str, endptr);
-}
-
-/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
-JSON_HEDLEY_NON_NULL(2)
-inline void strtof_by_type(long double& f, const char* str, char** endptr) noexcept
-{
-    f = std::strtold(str, endptr);
-}
-
-/// return the decimal point of the current locale
-inline char get_decimal_point() noexcept
-{
-    const auto* loc = localeconv();
-    JSON_ASSERT(loc != nullptr);
-    return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point);
-}
-
-/*!
-@brief convert a validated float token with strtof/strtod/strtold
-
-These functions expect the decimal point of the *current* locale, so it is
-looked up right before the conversion instead of once when the lexer is
-constructed: a locale change in between (by a parser callback, a SAX
-handler, or another thread) must not truncate the value (#5198). The
-token has been validated before, so if the conversion stops early and the
-decimal point changed in the meantime, the locale changed between the
-lookup and the call, and the conversion is repeated with the new decimal
-point. If the decimal point did not change, a retry cannot succeed: the
-locale's decimal point is not a single character (e.g., the two-byte
-U+066B of ar_EG.UTF-8 or fa_IR.UTF-8) and cannot be substituted in place.
-The value strtod parsed up to that point is kept, as before this change.
-
-Note that changing the locale in another thread *while* strtod runs is
-undefined behavior of the C library, which this function cannot prevent.
-
-@param[in,out] token                   the token with '.' as decimal point; its
-                                       decimal point is replaced during the
-                                       conversion and restored afterwards
-                                       (data() must be NUL-terminated)
-@param[in]     decimal_point_position  index of the '.' in @a token, or
-                                       std::string::npos if there is none
-@param[out]    value                   the converted value
-*/
-template<typename StringType, typename FloatType>
-void convert_float_locale_aware(StringType& token, std::size_t decimal_point_position, FloatType& value)
-{
-    const bool has_dot = decimal_point_position != std::string::npos;
-    char decimal_point = get_decimal_point();
-    for (;;)
-    {
-        const bool substitute = has_dot && decimal_point != '.';
-        if (substitute)
-        {
-            token[decimal_point_position] = static_cast<typename StringType::value_type>(decimal_point);
-        }
-
-        char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
-        strtof_by_type(value, token.data(), &endptr);
-
-        if (substitute)
-        {
-            // the caller hands the token on (e.g. to the SAX interface) with '.'
-            token[decimal_point_position] = '.';
-        }
-
-        if (JSON_HEDLEY_LIKELY(endptr == token.data() + token.size()))
-        {
-            return;
-        }
-
-        // retry only if the locale changed; otherwise, this would loop forever
-        const char current_decimal_point = get_decimal_point();
-        if (current_decimal_point == decimal_point)
-        {
-            return;
-        }
-        decimal_point = current_decimal_point;
-    }
-}
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/json.hpp

@@ -153,7 +153,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// workaround type for MSVC
     using basic_json_t = NLOHMANN_BASIC_JSON_TPL;
-    using json_base_class_t = ::nlohmann::detail::json_base_class<CustomBaseClass>;
 
   JSON_PRIVATE_UNLESS_TESTED:
     // convenience aliases for types residing in namespace detail;
@@ -213,6 +212,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     using cbor_tag_handler_t = detail::cbor_tag_handler_t;
     /// how to encode BJData
     using bjdata_version_t = detail::bjdata_version_t;
+    /// base class used to inject custom functionality into each instance of basic_json
+    /// @sa https://json.nlohmann.me/api/basic_json/json_base_class_t/
+    using json_base_class_t = ::nlohmann::detail::json_base_class<CustomBaseClass>;
     /// helper type for initializer lists of basic_json values
     using initializer_list_t = std::initializer_list<detail::json_ref<basic_json>>;
 
@@ -2690,6 +2692,20 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return *get_ptr<const binary_t*>();
     }
 
+    /// @brief access the custom base class
+    /// @sa https://json.nlohmann.me/api/basic_json/as_base_class/
+    json_base_class_t& as_base_class() noexcept
+    {
+        return static_cast<json_base_class_t&>(*this);
+    }
+
+    /// @brief access the custom base class
+    /// @sa https://json.nlohmann.me/api/basic_json/as_base_class/
+    const json_base_class_t& as_base_class() const noexcept
+    {
+        return static_cast<const json_base_class_t&>(*this);
+    }
+
     /// @}
 
     ////////////////////

single_include/nlohmann/json.hpp

@@ -8472,8 +8472,10 @@ NLOHMANN_JSON_NAMESPACE_END
 
 
 #include <array> // array
+#include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdio> // snprintf
+#include <cstdlib> // strtof, strtod, strtold, strtoll, strtoull
 #include <initializer_list> // initializer_list
 #include <string> // char_traits, string
 #include <utility> // move
@@ -8494,12 +8496,9 @@ NLOHMANN_JSON_NAMESPACE_END
 
 #include <array> // array
 #include <cfloat> // FLT_EVAL_METHOD
-#include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdint> // int64_t, uint64_t
-#include <cstdlib> // strtof, strtod, strtold
 #include <limits> // numeric_limits
-#include <string> // string
 
 // #include <nlohmann/detail/macro_scope.hpp>
 
@@ -8517,9 +8516,8 @@ NLOHMANN_JSON_NAMESPACE_END
 
 // This file contains the value-conversion helpers used by the lexer to turn an
 // already-validated number token into a value, without the locale/errno
-// overhead of std::strtoull/std::strtod where possible. They are free functions
-// so the lexer stays focused on scanning (see lexer::convert_number()) and so
-// that other parsers of JSON text can convert tokens exactly like it does.
+// overhead of std::strtoull/std::strtod. They are free functions so the lexer
+// stays focused on scanning; see lexer::convert_number().
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -8782,184 +8780,6 @@ bool parse_float_from_chars(const char* first, const char* last, FloatType& out)
 #endif
 }
 
-/*!
-@brief check whether Clinger's fast path can still succeed for a float token
-
-parse_float_fast() needs a significand below 2^53. A mantissa with 17 or
-more significant digits is at least 10^16 and therefore always exceeds it,
-so calling the fast path would walk the token one extra time only to
-decline before strtod has to run anyway.
-
-Significant digits are the mantissa's digits from the first nonzero one on;
-the sign, the decimal point, leading zeros, and the exponent do not count.
-The answer is derived from indices - the digits are not scanned again - so
-this stays off the hot path of the number scanners.
-
-@param[in] token                   the validated number token ('.' as decimal point)
-@param[in] decimal_point_position  index of the '.' in @a token, or
-                                   std::string::npos if there is none
-@param[in] mantissa_end            offset just past the last mantissa byte
-@return false if parse_float_fast() is guaranteed to decline
-*/
-inline bool mantissa_fits_clinger(const char* token, std::size_t decimal_point_position, std::size_t mantissa_end) noexcept
-{
-    // 10^16 already exceeds 2^53, so 17 digits can never fit
-    constexpr std::size_t limit = 17;
-
-    const std::size_t neg = (token[0] == '-') ? 1u : 0u;
-    const std::size_t has_dot = (decimal_point_position != std::string::npos) ? 1u : 0u;
-    // the JSON grammar restricts the integer part to "0" or [1-9][0-9]*, so
-    // a leading zero can only be a lone "0", which is not significant
-    const std::size_t lead_zero = (token[neg] == '0') ? 1u : 0u;
-    JSON_ASSERT(mantissa_end >= neg + has_dot + lead_zero);
-    std::size_t digits = mantissa_end - neg - has_dot - lead_zero;
-
-    if (JSON_HEDLEY_LIKELY(digits < limit))
-    {
-        return true;
-    }
-
-    // Only a number below 1 can carry further insignificant zeros, and only
-    // while the count stays at the limit does removing them change the
-    // answer - so this loop is skipped for all but a few tokens. The
-    // fraction is located through decimal_point_position rather than by
-    // searching '.'.
-    if (lead_zero != 0)
-    {
-        JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
-        for (std::size_t i = decimal_point_position + 1;
-                digits >= limit && i < mantissa_end && token[i] == '0'; ++i)
-        {
-            --digits;
-        }
-    }
-
-    return digits < limit;
-}
-
-/*!
-@brief convert a validated float token without the C library, if possible
-
-Tries std::from_chars (when available) and then Clinger's exact fast path
-(double only), skipping the latter when it cannot succeed.
-
-@param[in]  first                   pointer to the first character of the token
-@param[in]  last                    pointer past the last character
-@param[in]  decimal_point_position  index of the '.' in the token, or
-                                    std::string::npos if there is none
-@param[in]  mantissa_end            offset just past the last mantissa byte (the
-                                    index of 'e'/'E', or the token length)
-@param[out] value                   the converted value on success
-@return true if the value was converted; false if convert_float_locale_aware()
-        must convert it
-*/
-template<typename FloatType>
-bool convert_float_fast(const char* first, const char* last, std::size_t decimal_point_position,
-                        std::size_t mantissa_end, FloatType& value) noexcept
-{
-    if (parse_float_from_chars(first, last, value))
-    {
-        return true;
-    }
-    // Skipping a fast path that cannot succeed is lossless and saves a full
-    // extra pass over the token's bytes, which otherwise shows up on
-    // high-precision inputs such as canada.json
-    return mantissa_fits_clinger(first, decimal_point_position, mantissa_end)
-           && parse_float_fast(first, last, value);
-}
-
-/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
-JSON_HEDLEY_NON_NULL(2)
-inline void strtof_by_type(float& f, const char* str, char** endptr) noexcept
-{
-    f = std::strtof(str, endptr);
-}
-
-/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
-JSON_HEDLEY_NON_NULL(2)
-inline void strtof_by_type(double& f, const char* str, char** endptr) noexcept
-{
-    f = std::strtod(str, endptr);
-}
-
-/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
-JSON_HEDLEY_NON_NULL(2)
-inline void strtof_by_type(long double& f, const char* str, char** endptr) noexcept
-{
-    f = std::strtold(str, endptr);
-}
-
-/// return the decimal point of the current locale
-inline char get_decimal_point() noexcept
-{
-    const auto* loc = localeconv();
-    JSON_ASSERT(loc != nullptr);
-    return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point);
-}
-
-/*!
-@brief convert a validated float token with strtof/strtod/strtold
-
-These functions expect the decimal point of the *current* locale, so it is
-looked up right before the conversion instead of once when the lexer is
-constructed: a locale change in between (by a parser callback, a SAX
-handler, or another thread) must not truncate the value (#5198). The
-token has been validated before, so if the conversion stops early and the
-decimal point changed in the meantime, the locale changed between the
-lookup and the call, and the conversion is repeated with the new decimal
-point. If the decimal point did not change, a retry cannot succeed: the
-locale's decimal point is not a single character (e.g., the two-byte
-U+066B of ar_EG.UTF-8 or fa_IR.UTF-8) and cannot be substituted in place.
-The value strtod parsed up to that point is kept, as before this change.
-
-Note that changing the locale in another thread *while* strtod runs is
-undefined behavior of the C library, which this function cannot prevent.
-
-@param[in,out] token                   the token with '.' as decimal point; its
-                                       decimal point is replaced during the
-                                       conversion and restored afterwards
-                                       (data() must be NUL-terminated)
-@param[in]     decimal_point_position  index of the '.' in @a token, or
-                                       std::string::npos if there is none
-@param[out]    value                   the converted value
-*/
-template<typename StringType, typename FloatType>
-void convert_float_locale_aware(StringType& token, std::size_t decimal_point_position, FloatType& value)
-{
-    const bool has_dot = decimal_point_position != std::string::npos;
-    char decimal_point = get_decimal_point();
-    for (;;)
-    {
-        const bool substitute = has_dot && decimal_point != '.';
-        if (substitute)
-        {
-            token[decimal_point_position] = static_cast<typename StringType::value_type>(decimal_point);
-        }
-
-        char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
-        strtof_by_type(value, token.data(), &endptr);
-
-        if (substitute)
-        {
-            // the caller hands the token on (e.g. to the SAX interface) with '.'
-            token[decimal_point_position] = '.';
-        }
-
-        if (JSON_HEDLEY_LIKELY(endptr == token.data() + token.size()))
-        {
-            return;
-        }
-
-        // retry only if the locale changed; otherwise, this would loop forever
-        const char current_decimal_point = get_decimal_point();
-        if (current_decimal_point == decimal_point)
-        {
-            return;
-        }
-        decimal_point = current_decimal_point;
-    }
-}
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
 
@@ -9489,6 +9309,18 @@ class lexer : public lexer_base<BasicJsonType>
     ~lexer() = default;
 
   private:
+    /////////////////////
+    // locales
+    /////////////////////
+
+    /// return the decimal point of the current locale
+    static char get_decimal_point() noexcept
+    {
+        const auto* loc = localeconv();
+        JSON_ASSERT(loc != nullptr);
+        return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point);
+    }
+
     /////////////////////
     // scan functions
     /////////////////////
@@ -10296,6 +10128,24 @@ class lexer : public lexer_base<BasicJsonType>
         }
     }
 
+    JSON_HEDLEY_NON_NULL(2)
+    static void strtof(float& f, const char* str, char** endptr) noexcept
+    {
+        f = std::strtof(str, endptr);
+    }
+
+    JSON_HEDLEY_NON_NULL(2)
+    static void strtof(double& f, const char* str, char** endptr) noexcept
+    {
+        f = std::strtod(str, endptr);
+    }
+
+    JSON_HEDLEY_NON_NULL(2)
+    static void strtof(long double& f, const char* str, char** endptr) noexcept
+    {
+        f = std::strtold(str, endptr);
+    }
+
     /*!
     @brief scan a number literal
 
@@ -10335,7 +10185,7 @@ class lexer : public lexer_base<BasicJsonType>
     @note The scanner is independent of the current locale: token_buffer
           always holds `.`. Only the std::strtod fallback of convert_number()
           depends on the locale, and it looks up the decimal point right
-          before converting (see detail::convert_float_locale_aware()).
+          before converting (see convert_float_locale_aware()).
     */
     token_type scan_number()  // lgtm [cpp/use-of-goto] `goto` is used in this function to implement the number-parsing state machine described above. By design, any finite input will eventually reach the "done" state or return token_type::parse_error. In each intermediate state, 1 byte of the input is appended to the token_buffer vector, and only the already initialized variables token_buffer, number_type, and error_message are manipulated.
     {
@@ -10666,6 +10516,59 @@ scan_number_done:
         return token_type::uninitialized;
     }
 
+    /*!
+    @brief check whether Clinger's fast path can still succeed for this token
+
+    parse_float_fast() needs a significand below 2^53. A mantissa with 17 or
+    more significant digits is at least 10^16 and therefore always exceeds it,
+    so calling the fast path would walk the token one extra time only to
+    decline before strtod has to run anyway.
+
+    Significant digits are the mantissa's digits from the first nonzero one on;
+    the sign, the decimal point, leading zeros, and the exponent do not count.
+    The answer is derived from indices - the digits are not scanned again - so
+    this stays off the hot path of the number scanners.
+
+    @param[in] mantissa_end  offset just past the last mantissa byte in
+                             token_buffer
+    @return false if parse_float_fast() is guaranteed to decline
+    */
+    bool mantissa_fits_clinger(std::size_t mantissa_end) const
+    {
+        // 10^16 already exceeds 2^53, so 17 digits can never fit
+        constexpr std::size_t limit = 17;
+
+        const std::size_t neg = (!token_buffer.empty() && token_buffer[0] == '-') ? 1u : 0u;
+        const std::size_t has_dot = (decimal_point_position != std::string::npos) ? 1u : 0u;
+        // the JSON grammar restricts the integer part to "0" or [1-9][0-9]*, so
+        // a leading zero can only be a lone "0", which is not significant
+        const std::size_t lead_zero = (token_buffer[neg] == '0') ? 1u : 0u;
+        JSON_ASSERT(mantissa_end >= neg + has_dot + lead_zero);
+        std::size_t digits = mantissa_end - neg - has_dot - lead_zero;
+
+        if (JSON_HEDLEY_LIKELY(digits < limit))
+        {
+            return true;
+        }
+
+        // Only a number below 1 can carry further insignificant zeros, and only
+        // while the count stays at the limit does removing them change the
+        // answer - so this loop is skipped for all but a few tokens. The
+        // fraction is located through decimal_point_position rather than by
+        // searching '.'.
+        if (lead_zero != 0)
+        {
+            JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
+            for (std::size_t i = decimal_point_position + 1;
+                    digits >= limit && i < mantissa_end && token_buffer[i] == '0'; ++i)
+            {
+                --digits;
+            }
+        }
+
+        return digits < limit;
+    }
+
     /*!
     @brief convert the number text in token_buffer to its value and token type
 
@@ -10679,7 +10582,7 @@ scan_number_done:
                              token_buffer (the index of 'e'/'E', or
                              token_buffer.size() when there is no exponent);
                              used to skip Clinger's fast path when it cannot
-                             possibly succeed - see detail::mantissa_fits_clinger()
+                             possibly succeed - see mantissa_fits_clinger()
     */
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
@@ -10752,15 +10655,77 @@ scan_number_done:
         // (Eisel-Lemire, locale-independent, correctly rounded) when available;
         // otherwise the exact Clinger fast path (double only); otherwise the
         // locale-aware strtof/strtod/strtold.
-        if (convert_float_fast(num_begin, num_end, decimal_point_position, mantissa_end, value_float))
+        if (parse_float_from_chars(num_begin, num_end, value_float))
+        {
+            return token_type::value_float;
+        }
+        // Skipping a fast path that cannot succeed is lossless and saves a full
+        // extra pass over the token's bytes, which otherwise shows up on
+        // high-precision inputs such as canada.json
+        if (mantissa_fits_clinger(mantissa_end)
+                && parse_float_fast(num_begin, num_end, value_float))
         {
             return token_type::value_float;
         }
 
-        convert_float_locale_aware(token_buffer, decimal_point_position, value_float);
+        convert_float_locale_aware();
         return token_type::value_float;
     }
 
+    /*!
+    @brief convert the float in token_buffer with strtof/strtod/strtold
+
+    These functions expect the decimal point of the *current* locale, so it is
+    looked up right before the conversion instead of once when the lexer is
+    constructed: a locale change in between (by a parser callback, a SAX
+    handler, or another thread) must not truncate the value (#5198). The
+    token has been validated before, so if the conversion stops early and the
+    decimal point changed in the meantime, the locale changed between the
+    lookup and the call, and the conversion is repeated with the new decimal
+    point. If the decimal point did not change, a retry cannot succeed: the
+    locale's decimal point is not a single character (e.g., the two-byte
+    U+066B of ar_EG.UTF-8 or fa_IR.UTF-8) and cannot be substituted in place.
+    The value strtod parsed up to that point is kept, as before this change.
+
+    Note that changing the locale in another thread *while* strtod runs is
+    undefined behavior of the C library, which this function cannot prevent.
+    */
+    void convert_float_locale_aware()
+    {
+        const bool has_dot = decimal_point_position != std::string::npos;
+        char decimal_point = get_decimal_point();
+        for (;;)
+        {
+            const bool substitute = has_dot && decimal_point != '.';
+            if (substitute)
+            {
+                token_buffer[decimal_point_position] = static_cast<typename string_t::value_type>(decimal_point);
+            }
+
+            char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+            strtof(value_float, token_buffer.data(), &endptr);
+
+            if (substitute)
+            {
+                // get_string() hands the token to the SAX interface with '.'
+                token_buffer[decimal_point_position] = '.';
+            }
+
+            if (JSON_HEDLEY_LIKELY(endptr == token_buffer.data() + token_buffer.size()))
+            {
+                return;
+            }
+
+            // retry only if the locale changed; otherwise, this would loop forever
+            const char current_decimal_point = get_decimal_point();
+            if (current_decimal_point == decimal_point)
+            {
+                return;
+            }
+            decimal_point = current_decimal_point;
+        }
+    }
+
     /*!
     @brief contiguous fast path for scanning a number
 
@@ -26269,7 +26234,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// workaround type for MSVC
     using basic_json_t = NLOHMANN_BASIC_JSON_TPL;
-    using json_base_class_t = ::nlohmann::detail::json_base_class<CustomBaseClass>;
 
   JSON_PRIVATE_UNLESS_TESTED:
     // convenience aliases for types residing in namespace detail;
@@ -26329,6 +26293,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     using cbor_tag_handler_t = detail::cbor_tag_handler_t;
     /// how to encode BJData
     using bjdata_version_t = detail::bjdata_version_t;
+    /// base class used to inject custom functionality into each instance of basic_json
+    /// @sa https://json.nlohmann.me/api/basic_json/json_base_class_t/
+    using json_base_class_t = ::nlohmann::detail::json_base_class<CustomBaseClass>;
     /// helper type for initializer lists of basic_json values
     using initializer_list_t = std::initializer_list<detail::json_ref<basic_json>>;
 
@@ -28806,6 +28773,20 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return *get_ptr<const binary_t*>();
     }
 
+    /// @brief access the custom base class
+    /// @sa https://json.nlohmann.me/api/basic_json/as_base_class/
+    json_base_class_t& as_base_class() noexcept
+    {
+        return static_cast<json_base_class_t&>(*this);
+    }
+
+    /// @brief access the custom base class
+    /// @sa https://json.nlohmann.me/api/basic_json/as_base_class/
+    const json_base_class_t& as_base_class() const noexcept
+    {
+        return static_cast<const json_base_class_t&>(*this);
+    }
+
     /// @}
 
     ////////////////////

tests/src/unit-custom-base-class.cpp

@@ -9,6 +9,8 @@
 #include <set>
 #include <sstream>
 #include <string>
+#include <type_traits>
+#include <utility>
 
 #include "doctest_compatibility.h"
 
@@ -333,3 +335,71 @@ TEST_CASE("JSON Visit Node")
         );
     CHECK(expected.empty());
 }
+
+// Test accessing members of a custom base class that are hidden by members of nlohmann::basic_json
+class base_class_with_hidden_members
+{
+  public:
+    const char* type_name() const noexcept // NOLINT(readability-convert-member-functions-to-static)
+    {
+        return "custom type_name";
+    }
+
+    std::size_t size() const noexcept
+    {
+        return m_size;
+    }
+
+    std::size_t m_size = 42;
+};
+
+using json_with_hidden_base_members =
+    nlohmann::basic_json <
+    std::map,
+    std::vector,
+    std::string,
+    bool,
+    std::int64_t,
+    std::uint64_t,
+    double,
+    std::allocator,
+    nlohmann::adl_serializer,
+    std::vector<std::uint8_t>,
+    base_class_with_hidden_members
+    >;
+
+TEST_CASE("JSON Node as_base_class")
+{
+    using json = json_with_hidden_base_members;
+
+    static_assert(std::is_same<decltype(std::declval<json&>().as_base_class()), json::json_base_class_t&>::value, "");
+    static_assert(std::is_same<decltype(std::declval<const json&>().as_base_class()), const json::json_base_class_t&>::value, "");
+    static_assert(noexcept(std::declval<json&>().as_base_class()), "");
+    static_assert(noexcept(std::declval<const json&>().as_base_class()), "");
+
+    SECTION("non-const")
+    {
+        json j = {1, 2, 3};
+
+        CHECK(std::string(j.type_name()) == "array");
+        CHECK(j.size() == 3);
+        CHECK(std::string(j.as_base_class().type_name()) == "custom type_name");
+        CHECK(j.as_base_class().size() == 42);
+        CHECK(&j.as_base_class() == &static_cast<json::json_base_class_t&>(j));
+
+        j.as_base_class().m_size = 7;
+        CHECK(j.as_base_class().size() == 7);
+        CHECK(j.size() == 3);
+    }
+
+    SECTION("const")
+    {
+        const json j = {1, 2, 3};
+
+        CHECK(std::string(j.type_name()) == "array");
+        CHECK(j.size() == 3);
+        CHECK(std::string(j.as_base_class().type_name()) == "custom type_name");
+        CHECK(j.as_base_class().size() == 42);
+        CHECK(&j.as_base_class() == &static_cast<const json::json_base_class_t&>(j));
+    }
+}

tools/amalgamate/CHANGES.md

@@ -8,6 +8,3 @@ The following changes have been made to the code with respect to <https://github
   - membership check
   - made function from `_is_within`
   - removed unused variable `actual_path`
-- Added the optional config key `external`: include paths listed there are kept as
-  `#include` directives instead of being inlined (the first directive per path; the
-  repeated ones are commented out).

tools/amalgamate/README.md

@@ -57,11 +57,6 @@ Python v.2.7.0 or higher is required.
    amalgamation. Have a look at `test/source.c.json` and `test/include.h.json`
    to see two examples.
 
-   The optional `external` list names include paths that are kept as `#include`
-   directives instead of being inlined, e.g. `["nlohmann/json.hpp"]` for a header
-   that includes another amalgamated header. Only the first directive for each
-   of these paths is kept; the repeated ones are commented out.
-
  * The `-s, --source` option should specify the path to the source directory.
    This is useful for supporting separate source and build directories.
 

tools/amalgamate/amalgamate.py

@@ -62,10 +62,6 @@ class Amalgamation(object):
         return None
 
     def __init__(self, args):
-        # include paths that are kept as #include directives instead of
-        # being inlined (e.g. a header amalgamated on its own)
-        self.external = []
-        self.included_external = []
         with open(args.config, 'r') as f:
             config = json.loads(f.read())
             for key in config:
@@ -224,14 +220,11 @@ class TranslationUnit(object):
         while include_match:
             if not _is_within(include_match, skippable_contexts):
                 include_path = include_match.group("path")
-                if include_path in self.amalgamation.external:
-                    includes.append((include_match, None))
-                else:
-                    search_same_dir = include_match.group(1) == '"'
-                    found_included_path = self.amalgamation.find_included_file(
-                        include_path, self.file_dir if search_same_dir else None)
-                    if found_included_path:
-                        includes.append((include_match, found_included_path))
+                search_same_dir = include_match.group(1) == '"'
+                found_included_path = self.amalgamation.find_included_file(
+                    include_path, self.file_dir if search_same_dir else None)
+                if found_included_path:
+                    includes.append((include_match, found_included_path))
 
             include_match = self.include_pattern.search(self.content,
                                                         include_match.end())
@@ -242,17 +235,6 @@ class TranslationUnit(object):
         for include in includes:
             include_match, found_included_path = include
             tmp_content += self.content[prev_end:include_match.start()]
-            if found_included_path is None:
-                # an external header: keep the first directive and comment
-                # out the repeated ones
-                include_path = include_match.group("path")
-                if include_path in self.amalgamation.included_external:
-                    tmp_content += "// {0}".format(include_match.group(0))
-                else:
-                    self.amalgamation.included_external.append(include_path)
-                    tmp_content += include_match.group(0)
-                prev_end = include_match.end()
-                continue
             tmp_content += "// {0}\n".format(include_match.group(0))
             if found_included_path not in self.amalgamation.included_files:
                 t = TranslationUnit(found_included_path, self.amalgamation, False)

tools/amalgamate/config_json_view.json

@@ -1,9 +0,0 @@
-{
-	"project": "JSON for Modern C++",
-	"target": "single_include/nlohmann/json_view.hpp",
-	"sources": [
-		"include/nlohmann/json_view.hpp"
-	],
-	"include_paths": ["include"],
-	"external": ["nlohmann/json.hpp"]
-}