Bug #26399073: MYSQL DOES NOT COMPILE WITH CLANG ON WINDOWS [noclose]

Make MySQL build with Clang for Windows again; bump the recommended version
to 6.0 and fix a number of smaller issues that showed up.

We're nowhere near warning-free, but at least we seem to compile again now.

Change-Id: I54e834d8a5d96820bab62c68639cdb3c1bda28b0

Docs/README.build

@@ -75,19 +75,22 @@ see extra/README-wolfssl.txt on how to set this up.
 
 It is possible to compile with Clang on Windows, which compiles faster
 and also yields faster binaries, but this is experimental and not officially
-supported. To compile, use LLVM 5.0.0 or newer from releases.llvm.org
+supported. To compile, use LLVM 6.0.1 or newer from releases.llvm.org
 (Clang/C2, which is Microsoft's own version of Clang, is not supported),
 and put a Windows compile of Ninja in your path. Then execute the following
 in a shell:
 
   "c:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" amd64
-  set PATH=<path to Ninja>;c:\program files\llvm\msbuild-bin;%PATH%
+  set PATH=<path to Ninja>;%PATH%
   "c:\Program Files\CMake 3.8\bin\cmake.exe" -G Ninja -DCMAKE_C_COMPILER="c:/program files/llvm/msbuild-bin/cl.exe" -DCMAKE_CXX_COMPILER="c:/program files/llvm/msbuild-bin/cl.exe" -DCMAKE_LINKER="c:/program files/llvm/bin/lld-link.exe" -DWITH_BOOST=<path to Boost> ..
   ninja
 
 This configuration also supports ASAN (-DWITH_ASAN=1), although currently only
 when linking with MSVC's linker (not with LLD).
 
+For running tests with --parallel, you may need to add --build-thread= (500 is
+a reasonable value to try).
+
 ===
 
 Note: For building with unit tests, you need to tell cmake where to find

cmake/maintainer.cmake

@@ -66,6 +66,64 @@ IF(CMAKE_COMPILER_IS_GNUCXX)
   MY_ADD_CXX_WARNING_FLAG("Wimplicit-fallthrough=2")
 ENDIF()
 
+# Clang 6.0 and newer on Windows seems to enable -Weverything; turn off some
+# that are way too verbose for us.
+IF(WIN32 AND CMAKE_C_COMPILER_ID MATCHES "Clang")
+  # We don't need C++98 compatibility.
+  MY_ADD_CXX_WARNING_FLAG("Wno-c++98-compat")
+  MY_ADD_CXX_WARNING_FLAG("Wno-c++98-compat-pedantic")
+
+  # Also warns on using NULL.
+  MY_ADD_CXX_WARNING_FLAG("Wno-zero-as-null-pointer-constant")
+
+  # Should be enabled globally, but too noisy right now.
+  MY_ADD_CXX_WARNING_FLAG("Wno-old-style-cast")
+  MY_ADD_CXX_WARNING_FLAG("Wno-extra-semi")
+  MY_ADD_CXX_WARNING_FLAG("Wno-reserved-id-macro")
+  MY_ADD_CXX_WARNING_FLAG("Wno-documentation")
+  MY_ADD_CXX_WARNING_FLAG("Wno-documentation-pedantic")
+  MY_ADD_CXX_WARNING_FLAG("Wno-documentation-unknown-command")
+  MY_ADD_CXX_WARNING_FLAG("Wno-missing-variable-declarations")
+  MY_ADD_CXX_WARNING_FLAG("Wno-cast-qual")
+  MY_ADD_CXX_WARNING_FLAG("Wno-language-extension-token")
+  MY_ADD_CXX_WARNING_FLAG("Wno-shorten-64-to-32")
+  MY_ADD_CXX_WARNING_FLAG("Wno-shadow")
+  MY_ADD_CXX_WARNING_FLAG("Wno-deprecated")  # FIXME
+  MY_ADD_CXX_WARNING_FLAG("Wno-inconsistent-missing-destructor-override")
+  MY_ADD_CXX_WARNING_FLAG("Wno-c++2a-compat")
+  MY_ADD_CXX_WARNING_FLAG("Wno-macro-redefined")
+  MY_ADD_CXX_WARNING_FLAG("Wno-unused-const-variable")
+  MY_ADD_CXX_WARNING_FLAG("Wno-gnu-anonymous-struct")
+
+  # Various things we don't want to warn about.
+  MY_ADD_CXX_WARNING_FLAG("Wno-global-constructors")
+  MY_ADD_CXX_WARNING_FLAG("Wno-exit-time-destructors")
+  MY_ADD_CXX_WARNING_FLAG("Wno-undefined-func-template")
+  MY_ADD_CXX_WARNING_FLAG("Wno-nonportable-system-include-path")
+  MY_ADD_CXX_WARNING_FLAG("Wno-sign-conversion")
+  MY_ADD_CXX_WARNING_FLAG("Wno-unused-exception-parameter")
+  MY_ADD_CXX_WARNING_FLAG("Wno-missing-prototypes")
+  MY_ADD_CXX_WARNING_FLAG("Wno-shadow-field-in-constructor")
+  MY_ADD_CXX_WARNING_FLAG("Wno-float-equal")
+  MY_ADD_CXX_WARNING_FLAG("Wno-float-conversion")
+  MY_ADD_CXX_WARNING_FLAG("Wno-double-promotion")
+  MY_ADD_CXX_WARNING_FLAG("Wno-covered-switch-default")
+  MY_ADD_CXX_WARNING_FLAG("Wno-used-but-marked-unused")
+  MY_ADD_CXX_WARNING_FLAG("Wno-conversion")
+  MY_ADD_CXX_WARNING_FLAG("Wno-sign-conversion")
+  MY_ADD_CXX_WARNING_FLAG("Wno-microsoft-pure-definition")  # False positives.
+  MY_ADD_CXX_WARNING_FLAG("Wno-format-nonliteral")
+  MY_ADD_CXX_WARNING_FLAG("Wno-format-pedantic")
+  MY_ADD_CXX_WARNING_FLAG("Wno-cast-align")
+  MY_ADD_CXX_WARNING_FLAG("Wno-gnu-zero-variadic-macro-arguments")
+  MY_ADD_CXX_WARNING_FLAG("Wno-comma")
+  MY_ADD_CXX_WARNING_FLAG("Wno-sign-compare")
+  MY_ADD_CXX_WARNING_FLAG("Wno-switch-enum")
+  MY_ADD_CXX_WARNING_FLAG("Wno-implicit-fallthrough")  # Does not take the same signals as GCC.
+  MY_ADD_CXX_WARNING_FLAG("Wno-unused-macros")
+  MY_ADD_CXX_WARNING_FLAG("Wno-disabled-macro-expansion")
+ENDIF()
+
 #
 # Extra flags not supported on all versions/compilers
 #

cmake/os/Windows.cmake

@@ -81,6 +81,13 @@ IF(WITH_MSCRT_DEBUG)
   ADD_DEFINITIONS(-DMY_MSCRT_DEBUG)
   ADD_DEFINITIONS(-D_CRTDBG_MAP_ALLOC)
 ENDIF()
+
+IF(WIN32_CLANG)
+  # RapidJSON doesn't understand the Win32/Clang combination.
+  ADD_DEFINITIONS(-DRAPIDJSON_HAS_CXX11_RVALUE_REFS=1)
+  ADD_DEFINITIONS(-DRAPIDJSON_HAS_CXX11_NOEXCEPT=1)
+  ADD_DEFINITIONS(-DRAPIDJSON_HAS_CXX11_RANGE_FOR=1)
+ENDIF()
 
 OPTION(WIN_DEBUG_NO_INLINE "Disable inlining for debug builds on Windows" OFF)