mdbx: add workaround for old MSVC and/or old Windows SDK.

Resolves https://github.com/erthink/libmdbx/issues/265.

Change-Id: I295b5d9d5ecd670ccf258791bf87379a3ca17f21

CMakeLists.txt

@@ -365,7 +365,11 @@ endif()
 if(NOT DEFINED MDBX_C_STANDARD)
   # MSVC >= 19.28 (Microsoft Visual Studio 16.8) is mad!
   #               It unable process Windows SDK headers in the C11 mode!
-  if(HAS_C11 LESS 0 OR (MSVC AND MSVC_VERSION GREATER 1927))
+  if(MSVC AND MSVC_VERSION GREATER 1927 AND NOT MSVC_VERSION GREATER 1929)
+    set(MDBX_C_STANDARD 99)
+    set(C_FALLBACK_11 OFF)
+    set(C_FALLBACK_GNU11 OFF)
+  elseif(HAS_C11 LESS 0 AND NOT C_FALLBACK_GNU11 AND NOT C_FALLBACK_11)
     set(MDBX_C_STANDARD 99)
   else()
     set(MDBX_C_STANDARD 11)
@@ -573,8 +577,10 @@ macro(target_setup_options TARGET)
     set_target_properties(${TARGET} PROPERTIES
       INTERPROCEDURAL_OPTIMIZATION $<BOOL:${INTERPROCEDURAL_OPTIMIZATION}>)
   endif()
+  if(NOT C_FALLBACK_GNU11 AND NOT C_FALLBACK_11)
     set_target_properties(${TARGET} PROPERTIES
       C_STANDARD ${MDBX_C_STANDARD} C_STANDARD_REQUIRED ON)
+  endif()
   if(MDBX_BUILD_CXX)
     set_target_properties(${TARGET} PROPERTIES
       CXX_STANDARD ${MDBX_CXX_STANDARD} CXX_STANDARD_REQUIRED ON)
@@ -685,7 +691,7 @@ if(MDBX_BUILD_TOOLS)
 
   foreach(TOOL mdbx_chk mdbx_copy mdbx_stat mdbx_dump mdbx_load mdbx_drop)
     add_executable(${TOOL} mdbx.h ${MDBX_SOURCE_DIR}/${TOOL}.c ${WINGETOPT_SRC})
-    if(MDBX_C_STANDARD)
+    if(NOT C_FALLBACK_GNU11 AND NOT C_FALLBACK_11)
       set_target_properties(${TOOL} PROPERTIES
         C_STANDARD ${MDBX_C_STANDARD} C_STANDARD_REQUIRED ON)
     endif()

cmake/compiler.cmake

@@ -264,9 +264,24 @@ endif()
 if(CMAKE_CXX_COMPILER_LOADED)
   list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_11 HAS_CXX11)
   if(HAS_CXX11 LESS 0)
-    check_compiler_flag("-std=gnu++11" CXX_FALLBACK_STDGNU11)
+    check_cxx_compiler_flag("-std=gnu++11" CXX_FALLBACK_GNU11)
-    if(NOT CXX_FALLBACK_STDGNU11)
+    if(NOT CXX_FALLBACK_GNU11)
-      check_compiler_flag("-std=c++11" CXX_FALLBACK_STD11)
+      check_cxx_compiler_flag("-std=c++11" CXX_FALLBACK_11)
+    endif()
+  endif()
+endif()
+
+# Crutch for mad C compilers and/or CMake to enabling C11
+if(CMAKE_C_COMPILER_LOADED)
+  list(FIND CMAKE_C_COMPILE_FEATURES c_std_11 HAS_C11)
+  if(HAS_C11 LESS 0)
+    if (MSVC)
+      check_c_compiler_flag("/std:c11" C_FALLBACK_11)
+    else()
+      check_c_compiler_flag("-std=gnu11" C_FALLBACK_GNU11)
+      if(NOT C_FALLBACK_GNU11)
+        check_c_compiler_flag("-std=c11" C_FALLBACK_11)
+      endif()
     endif()
   endif()
 endif()
@@ -536,14 +551,24 @@ macro(setup_compile_flags)
   if(CMAKE_CXX_COMPILER_LOADED)
     set(CXX_FLAGS ${INITIAL_CMAKE_CXX_FLAGS})
     # Crutch for old C++ compilers and/or CMake to enabling C++11
-    if(CXX_FALLBACK_STDGNU11)
+    if(CXX_FALLBACK_GNU11)
       add_compile_flags("CXX" "-std=gnu++11")
-    elseif(CXX_FALLBACK_STD11)
+    elseif(CXX_FALLBACK_11)
       add_compile_flags("CXX" "-std=c++11")
     endif()
   endif()
   if(CMAKE_C_COMPILER_LOADED)
     set(C_FLAGS ${INITIAL_CMAKE_C_FLAGS})
+    # Crutch for mad C compilers and/or CMake to enabling C11
+    if(C_FALLBACK_GNU11)
+      add_compile_flags("C" "-std=gnu11")
+    elseif(C_FALLBACK_11)
+      if(MSVC)
+        add_compile_flags("C" "/std:c11")
+      else()
+        add_compile_flags("C" "-std=c11")
+      endif()
+    endif()
   endif()
   set(EXE_LINKER_FLAGS ${INITIAL_CMAKE_EXE_LINKER_FLAGS})
   set(SHARED_LINKER_FLAGS ${INITIAL_CMAKE_SHARED_LINKER_FLAGS})

src/internals.h

@@ -674,7 +674,7 @@ typedef struct MDBX_lockinfo {
   /* Marker to distinguish uniqueness of DB/CLK. */
   MDBX_atomic_uint64_t mti_bait_uniqueness;
 
-  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+  MDBX_ALIGNAS(MDBX_CACHELINE_SIZE) /* cacheline ----------------------------*/
 
 #if MDBX_ENABLE_PGOP_STAT
   /* Statistics of costly ops of all (running, completed and aborted)
@@ -682,7 +682,7 @@ typedef struct MDBX_lockinfo {
   MDBX_pgop_stat_t mti_pgop_stat;
 #endif /* MDBX_ENABLE_PGOP_STAT*/
 
-  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+  MDBX_ALIGNAS(MDBX_CACHELINE_SIZE) /* cacheline ----------------------------*/
 
   /* Write transaction lock. */
 #if MDBX_LOCKING > 0
@@ -708,7 +708,7 @@ typedef struct MDBX_lockinfo {
   /* Shared anchor for tracking readahead edge and enabled/disabled status. */
   pgno_t mti_readahead_anchor;
 
-  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+  MDBX_ALIGNAS(MDBX_CACHELINE_SIZE) /* cacheline ----------------------------*/
 
   /* Readeaders registration lock. */
 #if MDBX_LOCKING > 0
@@ -723,7 +723,7 @@ typedef struct MDBX_lockinfo {
 
 #if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
     (!defined(__cplusplus) && defined(_MSC_VER))
-  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+  MDBX_ALIGNAS(MDBX_CACHELINE_SIZE) /* cacheline ----------------------------*/
   MDBX_reader mti_readers[] /* dynamic size */;
 #endif /* C99 */
 } MDBX_lockinfo;

src/osal.h

@@ -56,18 +56,21 @@
 #include <string.h>
 #include <time.h>
 
-/* C11 stdalign.h */
+/* C11' alignas() */
 #if __has_include(<stdalign.h>)
 #include <stdalign.h>
-#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
-#define alignas(N) _Alignas(N)
-#elif defined(_MSC_VER)
-#define alignas(N) __declspec(align(N))
-#elif __has_attribute(__aligned__) || defined(__GNUC__)
-#define alignas(N) __attribute__((__aligned__(N)))
-#else
-#error "FIXME: Required _alignas() or equivalent."
 #endif
+#if defined(alignas) || defined(__cplusplus)
+#define MDBX_ALIGNAS(N) alignas(N)
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define MDBX_ALIGNAS(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define MDBX_ALIGNAS(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define MDBX_ALIGNAS(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required alignas() or equivalent."
+#endif /* MDBX_ALIGNAS */
 
 /*----------------------------------------------------------------------------*/
 /* Systems includes */