Fixed clang build on macOS

- Make sure to use dynamic linking on macOS to avoid OpenSSL static linking bug
- Use -std=c++17 in CFLAGS for files in contrib
- Avoid bad support for thread_local on macOS with clang altogether

CMakeLists.txt

@@ -139,6 +139,8 @@ else ()
     set (CMAKE_CXX_EXTENSIONS 0) # https://cmake.org/cmake/help/latest/prop_tgt/CXX_EXTENSIONS.html#prop_tgt:CXX_EXTENSIONS
     set (CMAKE_CXX_STANDARD_REQUIRED ON)
     set (CXX_FLAGS_INTERNAL_COMPILER "-std=c++1z")
+    # This needs to propagate to vendored projects in contrib
+    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
 endif ()
 
 set (CMAKE_BUILD_COLOR_MAKEFILE          ON)

cmake/find_openssl.cmake

@@ -1,6 +1,10 @@
 set (OPENSSL_USE_STATIC_LIBS ${USE_STATIC_LIBRARIES})
 if (APPLE)
     set (OPENSSL_ROOT_DIR "/usr/local/opt/openssl")
+    # https://rt.openssl.org/Ticket/Display.html?user=guest&pass=guest&id=2232
+    if (USE_STATIC_LIBRARIES)
+        message(WARNING "Disable USE_STATIC_LIBRARIES if you have linking problems with OpenSSL on MacOS")
+    endif ()
 endif ()
 find_package (OpenSSL)
 if (NOT OPENSSL_FOUND)

dbms/src/Common/MemoryTracker.cpp

@@ -149,7 +149,7 @@ void MemoryTracker::setOrRaiseLimit(Int64 value)
         ;
 }
 
-#if defined(__apple_build_version__) && __apple_build_version__ <= 9000038
+#if __APPLE__ && __clang__
 __thread MemoryTracker * current_memory_tracker = nullptr;
 #else
 thread_local MemoryTracker * current_memory_tracker = nullptr;

dbms/src/Common/MemoryTracker.h

@@ -108,7 +108,7 @@ public:
   * This pointer is set when memory consumption is monitored in current thread.
   * So, you just need to pass it to all the threads that handle one request.
   */
-#if defined(__apple_build_version__) && __apple_build_version__ <= 9000038
+#if __APPLE__ && __clang__
 extern __thread MemoryTracker * current_memory_tracker;
 #else
 extern thread_local MemoryTracker * current_memory_tracker;

dbms/src/DataStreams/CapnProtoRowInputStream.h

@@ -45,8 +45,8 @@ private:
     {
       enum Type { POP, PUSH, READ };
       Type type;
-      capnp::StructSchema::Field field;
-      size_t column;
+      capnp::StructSchema::Field field = {};
+      size_t column = 0;
     };
 
     // Wrapper for classes that could throw in destructor