mdbx: support for building by GCC 4.8

Change-Id: I4ad5c5be60233ae68936e0cbca1a0f01ec786bad

CMakeLists.txt

@@ -440,7 +440,7 @@ if(MDBX_CXX_STANDARD GREATER_EQUAL 11 AND MDBX_CXX_STANDARD LESS 83)
     option(MDBX_ENABLE_TESTS "Build MDBX tests" ${BUILD_TESTING})
   endif()
   if(NOT MDBX_AVOID_CRT
-      AND NOT (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5)
+      AND NOT (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
       AND NOT (CMAKE_COMPILER_IS_CLANG AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4)
       AND NOT (MSVC AND MSVC_VERSION LESS 1900))
     option(MDBX_BUILD_CXX "Build C++ portion" ON)

cmake/compiler.cmake

@@ -773,7 +773,7 @@ if(CMAKE_CXX_COMPILER_LOADED)
   # determine library for for std::filesystem
   set(LIBCXX_FILESYSTEM "")
   if(CMAKE_COMPILER_IS_GNUCXX)
-    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+    if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.3 AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
       set(LIBCXX_FILESYSTEM "stdc++fs")
     endif()
   elseif(CMAKE_COMPILER_IS_CLANG)

mdbx.h

@@ -396,8 +396,8 @@ typedef mode_t mdbx_mode_t;
 #define cxx07_constexpr_var const
 #elif !defined(__cpp_constexpr) || __cpp_constexpr < 200704L ||                \
     (defined(__LCC__) && __LCC__ < 124) ||                                     \
-    (defined(__GNUC__) && __GNUC__ < 5 && !defined(__clang__) &&               \
+    (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 407) &&           \
-     !defined(__LCC__)) ||                                                     \
+     !defined(__clang__) && !defined(__LCC__)) ||                              \
     (defined(_MSC_VER) && _MSC_VER < 1910) ||                                  \
     (defined(__clang__) && __clang_major__ < 4)
 #define cxx07_constexpr inline
@@ -1272,7 +1272,7 @@ enum MDBX_txn_flags_t {
  * will be ready for use with \ref mdbx_txn_renew(). This flag allows to
  * preallocate memory and assign a reader slot, thus avoiding these operations
  * at the next start of the transaction. */
-#if defined(__cplusplus) && defined(_MSC_VER) && _MSC_VER < 1910
+#if defined(__cplusplus) && !defined(__cpp_constexpr) && !defined(DOXYGEN)
   MDBX_TXN_RDONLY_PREPARE = uint32_t(MDBX_RDONLY) | uint32_t(MDBX_NOMEMINIT),
 #else
   MDBX_TXN_RDONLY_PREPARE = MDBX_RDONLY | MDBX_NOMEMINIT,

src/internals.h

@@ -1399,7 +1399,7 @@ ceil_powerof2(size_t value, size_t granularity) {
    MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
 #define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
 
-#if !(defined(__cplusplus) && defined(_MSC_VER) && _MSC_VER == 1900)
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
 static __maybe_unused void static_checks(void) {
   STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
                     "Oops, MDBX_MAX_DBI or CORE_DBS?");

test/config.cc

@@ -475,14 +475,24 @@ const std::string actor_config::serialize(const char *prefix) const {
   result.append(params.pathname_log);
   result.push_back('|');
 
+#if __cplusplus > 201400
   static_assert(std::is_trivially_copyable<actor_params_pod>::value,
                 "actor_params_pod should by POD");
+#else
+  static_assert(std::is_standard_layout<actor_params_pod>::value,
+                "actor_params_pod should by POD");
+#endif
   result.append(data2hex(static_cast<const actor_params_pod *>(&params),
                          sizeof(actor_params_pod), checksum));
   result.push_back('|');
 
+#if __cplusplus > 201400
   static_assert(std::is_trivially_copyable<actor_config_pod>::value,
                 "actor_config_pod should by POD");
+#else
+  static_assert(std::is_standard_layout<actor_config_pod>::value,
+                "actor_config_pod should by POD");
+#endif
   result.append(data2hex(static_cast<const actor_config_pod *>(this),
                          sizeof(actor_config_pod), checksum));
   result.push_back('|');
@@ -527,8 +537,13 @@ bool actor_config::deserialize(const char *str, actor_config &config) {
     TRACE("<< actor_config::deserialize: slash-3\n");
     return false;
   }
+#if __cplusplus > 201400
   static_assert(std::is_trivially_copyable<actor_params_pod>::value,
                 "actor_params_pod should by POD");
+#else
+  static_assert(std::is_standard_layout<actor_params_pod>::value,
+                "actor_params_pod should by POD");
+#endif
   if (!hex2data(str, slash, static_cast<actor_params_pod *>(&config.params),
                 sizeof(actor_params_pod), checksum)) {
     TRACE("<< actor_config::deserialize: actor_params_pod(%.*s)\n",
@@ -542,8 +557,13 @@ bool actor_config::deserialize(const char *str, actor_config &config) {
     TRACE("<< actor_config::deserialize: slash-4\n");
     return false;
   }
+#if __cplusplus > 201400
   static_assert(std::is_trivially_copyable<actor_config_pod>::value,
                 "actor_config_pod should by POD");
+#else
+  static_assert(std::is_standard_layout<actor_config_pod>::value,
+                "actor_config_pod should by POD");
+#endif
   if (!hex2data(str, slash, static_cast<actor_config_pod *>(&config),
                 sizeof(actor_config_pod), checksum)) {
     TRACE("<< actor_config::deserialize: actor_config_pod(%.*s)\n",

test/keygen.cc

@@ -198,7 +198,7 @@ void __hot maker::pair(serial_t serial, const buffer &key, buffer &value,
 
 void maker::setup(const config::actor_params_pod &actor, unsigned actor_id,
                   unsigned thread_number) {
-#if !defined(_MSC_VER) || _MSC_VER > 1900
+#if defined(__cpp_constexpr)
   static_assert(unsigned(MDBX_INTEGERKEY | MDBX_REVERSEKEY | MDBX_DUPSORT |
                          MDBX_INTEGERDUP | MDBX_REVERSEDUP) < UINT16_MAX,
                 "WTF?");
@@ -317,7 +317,7 @@ void __hot maker::mk_begin(const serial_t serial, const essentials &params,
 
 void __hot maker::mk_continue(const serial_t serial, const essentials &params,
                               result &out) {
-#if !defined(_MSC_VER) || _MSC_VER > 1900
+#if defined(__cpp_constexpr)
   static_assert(
       (essentials::prng_fill_flag &
        unsigned(MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_INTEGERKEY |