[LLDB] Ensure LLDB symbols are exported in LLDB_EXPORT_ALL_SYMBOLS is provided.

[wallace]

Summary

If we want to export all lldb symbols (i.e LLDB_EXPORT_ALL_SYMBOLS=ON), we need to use default visibility for all LLDB libraries even if a global CMAKE_CXX_VISIBILITY_PRESET=hidden is present. In fact, there are cases in which a global llvm configuration wants CMAKE_CXX_VISIBILITY_PRESET as hidden but simultaneously LLDB_EXPORT_ALL_SYMBOLS=ON is also needed to be able to develop out-of-tree lldb plugins.

[wallace]

nits

[wallace]

another nit...

[rriddle]

lldb/cmake/modules/AddLLDB.cmake

173

Other places uses if (NOT CMAKE_SYSTEM_NAME MATCHES "Windows") to check for non-windows, should that check be used here as well? Not sure what's consistent for the lldb codebase.

[wallace]

lldb/cmake/modules/AddLLDB.cmake

173

I initially thought that it might be fine just to check the compiler id, but better be safer gating the target OS as well.

[wallace]

gate the target OS

[rriddle]

LGTM, and makes sense to me given that downstream users often want a build of LLVM with CMAKE_CXX_VISIBILITY_PRESET=hidden, but lldb should still be able to build/link/work in the presence of that (the LLDB driver and tools currently fail to link if LLVM is built CMAKE_CXX_VISIBILITY_PRESET=hidden).

[JDevlieghere]

lldb/cmake/modules/AddLLDB.cmake

175

Rather than changing the compile options directly, can we change the CXX_VISIBILITY_PRESET property?

set_target_properties((${name} PROPERTIES CXX_VISIBILITY_PRESET default)

[wallace]

lldb/cmake/modules/AddLLDB.cmake

175

Thanks @JDevlieghere , that works and is cleaner

[wallace]

Address comments

[JDevlieghere]

Thanks! LGTM

lldb/cmake/modules/AddLLDB.cmake

if(PARAM_PLUGIN)
     get_property(parent_dir DIRECTORY PROPERTY PARENT_DIRECTORY)
     if(EXISTS ${parent_dir})
       get_filename_component(category ${parent_dir} NAME)
       set_target_properties(${name} PROPERTIES FOLDER "lldb plugins/${category}")
     endif()
   else()
     set_target_properties(${name} PROPERTIES FOLDER "lldb libraries")
   endif()
+
+  # If we want to export all lldb symbols (i.e LLDB_EXPORT_ALL_SYMBOLS=ON), we
+  # need to use default visibility for all LLDB libraries even if a global
+  # `CMAKE_CXX_VISIBILITY_PRESET=hidden`is present.
+  if (LLDB_EXPORT_ALL_SYMBOLS)
+    set_target_properties(${name} PROPERTIES CXX_VISIBILITY_PRESET default)
+  endif()
 endfunction(add_lldb_library)
 
 function(add_lldb_executable name)
   cmake_parse_arguments(ARG
     "GENERATE_INSTALL"
     "INSTALL_PREFIX;ENTITLEMENTS"
     "LINK_LIBS;CLANG_LIBS;LINK_COMPONENTS;BUILD_RPATH;INSTALL_RPATH"
     ${ARGN}
     )