Make sure to build libc++abi without -fsanitize=vptr.

The existing suppression that dealt with this will stop working after
a libc++abi roll.

Bug: 1181057,609786
Change-Id: I8a4716d90a0a20de622dbb8c15daab1d44aec473
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2716602
Commit-Queue: Nico Weber <thakis@chromium.org>
Commit-Queue: Arthur Eubanks <aeubanks@google.com>
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Arthur Eubanks <aeubanks@google.com>
Cr-Commit-Position: refs/heads/master@{#856913}

buildtools/third_party/libc++abi/BUILD.gn

@@ -74,6 +74,14 @@ source_set("libc++abi") {
     "//buildtools/third_party/libc++:config",
   ]
 
+  # private_typeinfo.cpp implements __dynamic_cast(), which is the runtime
+  # bit that implements dynamic_cast<>(). But ubsan's vptr check inserts
+  # dynamic_cast<>()s, which leads to infinite recursion. So make sure we don't
+  # pass -fsanitize=vptr.
+  configs -= [ "//build/config/sanitizers:default_sanitizer_flags" ]
+  configs +=
+      [ "//build/config/sanitizers:default_sanitizer_flags_but_ubsan_vptr" ]
+
   if (export_libcxxabi_from_executables || libcxx_is_shared) {
     configs -= [ "//build/config/gcc:symbol_visibility_hidden" ]
     configs += [ "//build/config/gcc:symbol_visibility_default" ]

tools/ubsan/vptr_blacklist.txt

@@ -124,9 +124,3 @@ type:*StartPageService*
 # Remove once function attribute level blacklisting is implemented.
 # See crbug.com/476063.
 fun:*forbidGCDuringConstruction*
-
-#############################################################################
-# UBsan goes into an infinite recursion when __dynamic_cast instrumented with
-# "vptr". See crbug.com/609786.
-
-src:*/third_party/libc\+\+abi/trunk/src/private_typeinfo.cpp