CMake: Disable ENABLE_EXPORTS for executables with MSVC

The MSVC linker won't produce a .lib file for an executable that doesn't
export anything, and LLVM doesn't maintain dllexport annotations or .def
files listing all C++ symbols. It also doesn't support exporting all
symbols, like binutils ld.

CMake 3.2 changed the Ninja generator to list both the .exe and .lib
files as outputs of executable build targets. Ninja would always re-link
executables with ENABLE_EXPORTS because the .lib output file was not
present, and therefore the target was out of date.

llvm-svn: 232662

CMakeLists.txt

@@ -557,7 +557,7 @@ if( ${CMAKE_SYSTEM_NAME} MATCHES SunOS )
 endif( ${CMAKE_SYSTEM_NAME} MATCHES SunOS )
 
 # Make sure we don't get -rdynamic in every binary. For those that need it,
-# use set_target_properties(target PROPERTIES ENABLE_EXPORTS 1)
+# use export_executable_symbols(target).
 set(CMAKE_SHARED_LIBRARY_LINK_CXX_FLAGS "")
 
 include(AddLLVM)

cmake/modules/AddLLVM.cmake

@@ -490,6 +490,12 @@ macro(add_llvm_executable name)
   endif( LLVM_COMMON_DEPENDS )
 endmacro(add_llvm_executable name)
 
+function(export_executable_symbols target)
+  if (NOT MSVC) # MSVC's linker doesn't support exporting all symbols.
+    set_target_properties(${target} PROPERTIES ENABLE_EXPORTS 1)
+  endif()
+endfunction()
+
 
 set (LLVM_TOOLCHAIN_TOOLS
   llvm-ar

examples/ExceptionDemo/CMakeLists.txt

@@ -15,4 +15,4 @@ add_llvm_example(ExceptionDemo
   ExceptionDemo.cpp
   )
 
-set_target_properties(ExceptionDemo PROPERTIES ENABLE_EXPORTS 1)
+export_executable_symbols(ExceptionDemo)

tools/bugpoint/CMakeLists.txt

@@ -31,7 +31,7 @@ add_llvm_tool(bugpoint
   ToolRunner.cpp
   bugpoint.cpp
   )
-set_target_properties(bugpoint PROPERTIES ENABLE_EXPORTS 1)
+export_executable_symbols(bugpoint)
 
 if(WITH_POLLY AND LINK_POLLY_INTO_TOOLS)
   target_link_libraries(bugpoint Polly)

tools/llc/CMakeLists.txt

@@ -17,4 +17,4 @@ set(LLVM_NO_DEAD_STRIP 1)
 add_llvm_tool(llc
   llc.cpp
   )
-set_target_properties(llc PROPERTIES ENABLE_EXPORTS 1)
+export_executable_symbols(llc)

tools/lli/CMakeLists.txt

@@ -39,4 +39,4 @@ add_llvm_tool(lli
   RemoteTarget.cpp
   RemoteTargetExternal.cpp
   )
-set_target_properties(lli PROPERTIES ENABLE_EXPORTS 1)
+export_executable_symbols(llvm-stress)

tools/llvm-stress/CMakeLists.txt

@@ -7,4 +7,4 @@ set(LLVM_LINK_COMPONENTS
 add_llvm_tool(llvm-stress
   llvm-stress.cpp
   )
-set_target_properties(llvm-stress PROPERTIES ENABLE_EXPORTS 1)
+export_executable_symbols(llvm-stress)

tools/opt/CMakeLists.txt

@@ -31,7 +31,7 @@ add_llvm_tool(opt
   PrintSCC.cpp
   opt.cpp
   )
-set_target_properties(opt PROPERTIES ENABLE_EXPORTS 1)
+export_executable_symbols(opt)
 
 if(WITH_POLLY AND LINK_POLLY_INTO_TOOLS)
   target_link_libraries(opt Polly)