Force hidden symbol visibility for allocation operators

third_party/libc++/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
 
 # Sanitizer builds need to override operator new, operator delete, and
 # some exception handling symbols, so libc++ must be a shared library
 # to prevent duplicate symbol errors when linking.
@@ skipping 80 matching lines @@
     "trunk/src/stdexcept.cpp",
     "trunk/src/string.cpp",
     "trunk/src/strstream.cpp",
     "trunk/src/system_error.cpp",
     "trunk/src/thread.cpp",
     "trunk/src/typeinfo.cpp",
     "trunk/src/utility.cpp",
     "trunk/src/valarray.cpp",
     "trunk/src/variant.cpp",
   ]
+  if (libcpp_is_static) {
+    # Current gcc and clang do not allow declaring several allocation
+    # operators with hidden visibility [1] [2], however we don't want
+    # these symbols exported on static builds.  This is a workaround
+    # that takes advantage of an ELF visibility merging rule that
+    # picks the "most hidden" visibility of all versions of a symbol,
+    # even if the symbol is undefined.
+    #
+    # [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81107
+    # [2] https://bugs.llvm.org/show_bug.cgi?id=33473
+    sources += [ "alloc_visibility_overrides.S" ]
+  }
   configs -= [
     "//build/config/compiler:chromium_code",
     "//build/config/compiler:no_rtti",
     "//build/config/gcc:no_exceptions",
   ]
   configs += [
     ":config",
     ":no_libstdcpp",
     "//build/config/compiler:no_chromium_code",
     "//build/config/compiler:rtti",
@@ skipping 24 matching lines @@
       # Normally the generator takes care of RPATH. Our case is special because
       # the generator is unaware of the libc++.so dependency. Note that setting
       # RPATH here is a potential security issue. See the following for another
       # example of this issue: https://code.google.com/p/gyp/issues/detail?id=315
       "-Wl,-rpath,\$ORIGIN/",
     ]
   }
 
   lib_dirs = [ root_build_dir ]
 }