mdbx-docs: fix/refine C++ API docs by Doxygen.

docs/Doxyfile.in

@@ -424,7 +424,7 @@ SUBGROUPING            = YES
 # SEPARATE_MEMBER_PAGES.
 # The default value is: NO.
 
-INLINE_GROUPED_CLASSES = NO
+INLINE_GROUPED_CLASSES = YES
 
 # When the INLINE_SIMPLE_STRUCTS tag is set to YES, structs, classes, and unions
 # with only public data fields or simple typedef fields will be shown inline in
@@ -434,7 +434,7 @@ INLINE_GROUPED_CLASSES = NO
 # Man pages) or section (for LaTeX and RTF).
 # The default value is: NO.
 
-INLINE_SIMPLE_STRUCTS  = NO
+INLINE_SIMPLE_STRUCTS  = YES
 
 # When TYPEDEF_HIDES_STRUCT tag is enabled, a typedef of a struct, union, or
 # enum is documented as struct, union, or enum with the name of the typedef. So
@@ -660,7 +660,7 @@ SORT_BRIEF_DOCS        = NO
 # detailed member documentation.
 # The default value is: NO.
 
-SORT_MEMBERS_CTORS_1ST = NO
+SORT_MEMBERS_CTORS_1ST = YES
 
 # If the SORT_GROUP_NAMES tag is set to YES then doxygen will sort the hierarchy
 # of group names into alphabetical order. If set to NO the group names will
@@ -941,7 +941,12 @@ EXCLUDE_PATTERNS       =
 # Note that the wildcards are matched against the file with absolute path, so to
 # exclude all test directories use the pattern */test/*
 
-EXCLUDE_SYMBOLS        =
+EXCLUDE_SYMBOLS        = NOMINMAX __ORDER_BIG_ENDIAN__ __ORDER_LITTLE_ENDIAN__ \
+	 __has_include __has_attribute __has_builtin __has_cpp_attribute __has_extension __has_feature \
+	HAVE_STRUCT_IOVEC MDBX_STRINGIFY_HELPER MDBX_STRINGIFY \
+	MDBX_NOSANITIZE_ENUM MDBX_PRINTF_ARGS \
+	CONSTEXPR_ENUM_FLAGS_OPERATIONS DEFINE_ENUM_FLAG_OPERATORS \
+	bool false true __dll_export __dll_import
 
 # The EXAMPLE_PATH tag can be used to specify one or more files or directories
 # that contain example code fragments that are included (see the \include
@@ -2216,7 +2221,12 @@ INCLUDE_FILE_PATTERNS  =
 # recursively expanded use the := operator instead of the = operator.
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
-PREDEFINED             = DOXYGEN
+PREDEFINED             = DOXYGEN MDBX_DECLARE_EXCEPTION \
+	MDBX_CXX01_CONSTEXPR MDBX_CXX01_CONSTEXPR_VAR \
+	MDBX_CXX11_CONSTEXPR MDBX_CXX11_CONSTEXPR_VAR \
+	MDBX_CXX14_CONSTEXPR MDBX_CXX14_CONSTEXPR_VAR \
+	MDBX_CXX17_CONSTEXPR MDBX_CXX20_CONSTEXPR \
+	MDBX_CXX17_NOEXCEPT
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
 # tag can be used to specify a list of macro names that should be expanded. The

mdbx.h

@@ -209,7 +209,8 @@ typedef mode_t mdbx_mode_t;
 #pragma warning(pop)
 #endif
 
-/** @} close c_api
+/** end of c_api @}
+ *
  * \defgroup api_macros Common Macros
  * @{ */
 
@@ -574,7 +575,7 @@ typedef mode_t mdbx_mode_t;
 
 #endif /* DEFINE_ENUM_FLAG_OPERATORS */
 
-/** @} end of Common Macros */
+/** end of api_macros @} */
 
 /*----------------------------------------------------------------------------*/
 
@@ -961,7 +962,7 @@ LIBMDBX_API const char *mdbx_dump_val(const MDBX_val *key, char *const buf,
 /** \brief Panics with message and causes abnormal process termination. */
 LIBMDBX_API void mdbx_panic(const char *fmt, ...) MDBX_PRINTF_ARGS(1, 2);
 
-/** @} end of logging & debug */
+/** end of c_debug @} */
 
 /** \brief Environment flags
  * \ingroup c_opening
@@ -1361,7 +1362,7 @@ enum MDBX_env_flags_t {
    * \ref mdbx_txn_begin() for particular write transaction. \see sync_modes */
   MDBX_UTTERLY_NOSYNC = MDBX_SAFE_NOSYNC | UINT32_C(0x100000),
 
-  /** @} end of SYNC MODES */
+  /** end of sync_modes @} */
 };
 #ifndef __cplusplus
 /** \ingroup c_opening */
@@ -3806,7 +3807,7 @@ MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_INLINE_API(uint32_t, mdbx_key_from_int32,
                                                (const int32_t i32)) {
   return UINT32_C(0x80000000) + i32;
 }
-/** @} */
+/** end of value2key @} */
 
 /** \defgroup key2value Key-to-Value functions
  * \brief Key-to-Value functions to
@@ -3827,7 +3828,7 @@ mdbx_int32_from_key(const MDBX_val);
 
 MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int64_t
 mdbx_int64_from_key(const MDBX_val);
-/** @} */
+/** end of value2key @} */
 
 /** \brief Retrieve statistics for a database.
  * \ingroup c_statinfo
@@ -5100,7 +5101,7 @@ LIBMDBX_API int mdbx_env_open_for_recovery(MDBX_env *env, const char *pathname,
  * leg(s). */
 LIBMDBX_API int mdbx_env_turn_for_recovery(MDBX_env *env, unsigned target_meta);
 
-/** @} B-tree Traversal */
+/** end of btree_traversal @} */
 
 /**** Attribute support functions for Nexenta (scheduled for removal)
  * *****************************************************************/
@@ -5270,10 +5271,10 @@ LIBMDBX_API int mdbx_cursor_get_attr(MDBX_cursor *cursor, MDBX_val *key,
  * \retval MDBX_EINVAL    An invalid parameter was specified. */
 LIBMDBX_API int mdbx_get_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
                               MDBX_val *data, mdbx_attr_t *pattr);
-/** @} end of Attribute support functions for Nexenta */
+/** end of nexenta @} */
 #endif /* MDBX_NEXENTA_ATTRS */
 
-/** @} end of C API */
+/** end of c_api @} */
 
 /*******************************************************************************
  * Workaround for mmaped-lookahead-cross-page-boundary bug

mdbx.h++

@@ -256,11 +256,13 @@
 #endif                          /* _MSC_VER (warnings) */
 
 //------------------------------------------------------------------------------
+/// \brief The libmdbx C++ API namespace
+/// \ingroup cxx_api
+namespace mdbx {
+
 /// \defgroup cxx_api C++ API
 /// @{
 
-namespace mdbx {
-
 // Functions whose signature depends on the `mdbx::byte` type
 // must be strictly defined as inline!
 #if defined(DOXYGEN) || (defined(__cpp_char8_t) && __cpp_char8_t >= 201811)
@@ -352,6 +354,9 @@ using path = ::std::wstring;
 using path = ::std::string;
 #endif /* mdbx::path */
 
+/// \defgroup cxx_exceptions exceptions and errors
+/// @{
+
 /// \brief Transfers C++ exceptions thru C callbacks.
 /// \details Implements saving exceptions before returning
 /// from an C++'s environment to the intermediate C code and re-throwing after
@@ -507,11 +512,17 @@ static MDBX_CXX14_CONSTEXPR size_t check_length(size_t headroom,
                                                 size_t payload);
 static MDBX_CXX14_CONSTEXPR size_t check_length(size_t headroom, size_t payload,
                                                 size_t tailroom);
+
+/// end of cxx_exceptions @}
+
 static MDBX_CXX17_CONSTEXPR size_t strlen(const char *c_str) noexcept;
 static MDBX_CXX20_CONSTEXPR void *memcpy(void *dest, const void *src,
                                          size_t bytes) noexcept;
 //------------------------------------------------------------------------------
 
+/// \defgroup cxx_data slices and buffers
+/// @{
+
 #if MDBX_HAVE_CXX20_CONCEPTS
 
 template <typename T>
@@ -2741,6 +2752,8 @@ struct pair_result : public pair {
   }
 };
 
+/// end of cxx_data @}
+
 //------------------------------------------------------------------------------
 
 /// \brief Loop control constants for readers enumeration functor and other
@@ -5877,12 +5890,18 @@ inline bool cursor::erase(const slice &key, const slice &value) {
   return data.done && erase();
 }
 
+/// end cxx_api @}
 } // namespace mdbx
 
 //------------------------------------------------------------------------------
 
+/// \brief The `std:: namespace part of libmdbx C++ API
+/// \ingroup cxx_api
 namespace std {
 
+/// \defgroup cxx_api C++ API
+/// @{
+
 inline string to_string(const ::mdbx::slice &value) {
   ostringstream out;
   out << value;
@@ -5974,10 +5993,9 @@ template <> struct hash<::mdbx::slice> {
   }
 };
 
+/// end cxx_api @}
 } // namespace std
 
 #ifdef _MSC_VER
 #pragma warning(pop)
 #endif
-
-/// @} end of C++ API