[ubsan] Have -fsanitize=vptr emit a null check if -fsanitize=null isn't available

In r309007, I made -fsanitize=null a hard prerequisite for -fsanitize=vptr. I
did not see the need for the two checks to have separate null checking logic
for the same pointer. I expected the two checks to either always be enabled
together, or to be mutually compatible.

In the mailing list discussion re: r309007 it became clear that that isn't the
case. If a codebase is -fsanitize=vptr clean but not -fsanitize=null clean,
it's useful to have -fsanitize=vptr emit its own null check. That's what this
patch does: with it, -fsanitize=vptr can be used without -fsanitize=null.

Differential Revision: https://reviews.llvm.org/D36112

llvm-svn: 309846

1 files changed, 0 insertions, 7 deletions

diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index f4fe06af25f..2a3ae51734d 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -307,13 +307,6 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
     Kinds &= ~Vptr;
   }
 
-  // Disable -fsanitize=vptr if -fsanitize=null is not enabled (the vptr
-  // instrumentation is broken without run-time null checks).
-  if ((Kinds & Vptr) && !(Kinds & Null)) {
-    Kinds &= ~Vptr;
-    D.Diag(diag::warn_drv_disabling_vptr_no_null_check);
-  }
-
   // Check that LTO is enabled if we need it.
   if ((Kinds & NeedsLTO) && !D.isUsingLTO()) {
     D.Diag(diag::err_drv_argument_only_allowed_with)