Try to fully control the mode of clang visibility macros from CMake

Author: fsfod

clang/cmake/modules/AddClang.cmake

@@ -108,8 +108,15 @@ macro(add_clang_library name)
   endif()
   llvm_add_library(${name} ${LIBTYPE} ${ARG_UNPARSED_ARGUMENTS} ${srcs})
 
-  if(NOT ARG_SHARED AND NOT ARG_STATIC)
-    target_compile_definitions("obj.${name}" PRIVATE CLANG_EXPORTS)
+  if(MSVC AND NOT CLANG_LINK_CLANG_DYLIB)
+    # Make sure all consumers also turn off visibility macros so there not trying to dllimport symbols.
+    target_compile_definitions(${name} PUBLIC CLANG_BUILD_STATIC)
+    if(TARGET "obj.${name}")
+      target_compile_definitions("obj.${name}" PUBLIC CLANG_BUILD_STATIC)
+    endif()
+  elseif(NOT ARG_SHARED AND NOT ARG_STATIC)
+    # Clang component libraries linked in to clang-cpp are declared without SHARED or STATIC
+    target_compile_definitions("obj.${name}" PUBLIC CLANG_EXPORTS)
   endif()
 
   set(libs ${name})

clang/include/clang/Support/Compiler.h

@@ -31,7 +31,6 @@
 // Marker to add to classes or functions in public headers that should not have
 // export macros added to them by the clang tool
 #define CLANG_ABI_NOT_EXPORTED
-#if defined(LLVM_BUILD_LLVM_DYLIB) || defined(LLVM_BUILD_SHARED_LIBS)
 // Some libraries like those for tablegen are linked in to tools that used
 // in the build so can't depend on the llvm shared library. If export macros
 // were left enabled when building these we would get duplicate or
@@ -64,6 +63,5 @@
 #define CLANG_TEMPLATE_ABI
 #define CLANG_EXPORT_TEMPLATE
 #endif
-#endif
 
 #endif