[cmake] Add linker option "-Wl,-z,defs" in standalone build

mgorny · mgorny · commit 4601ac04c738 · 2016-09-27T12:15:35.000Z
Add the "-Wl,-z,defs" linker option that is used to prevent underlinking. It is already used by LLVM itself but does not get propagated into stand-alone build of libc++. This patch ensures that the option is passed in independently of whether libc++ is built in-tree or out-of-tree. Patch by Lei Zhang. Differential Revision: https://reviews.llvm.org/D24119 llvm-svn: 282483
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
@@ -319,6 +319,18 @@ remove_flags(-stdlib=libc++ -stdlib=libstdc++)
 # so they don't get transformed into -Wno and -errors respectivly.
 remove_flags(-Wno-pedantic -pedantic-errors -pedantic)
 
+# FIXME: this is cribbed from HandleLLVMOptions.cmake.
+if(LIBCXX_STANDALONE_BUILD)
+  # Pass -Wl,-z,defs. This makes sure all symbols are defined. Otherwise a DSO
+  # build might work on ELF but fail on MachO/COFF.
+  if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin" OR WIN32 OR CYGWIN OR
+          ${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD" OR
+          ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD") AND
+     NOT LLVM_USE_SANITIZER)
+    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,defs")
+  endif()
+endif()
+
 # Required flags ==============================================================
 set(LIBCXX_STANDARD_VER c++11 CACHE INTERNAL "internal option to change build dialect")
 add_compile_flags_if_supported(-std=${LIBCXX_STANDARD_VER})
