[CFI] Diagnose when we CFI in diagnostic mode is unavailable on a toolchain.

Summary:
Namely, we must have proper C++ABI support in UBSan runtime. We don't
have a good way to check for that, so just assume that C++ABI support is
there whenever -fsanitize=vptr is supported (i.e. only on handful of
platforms).

Exact diagnostic is also tricky. It's not "cfi" that is unsupported,
just the diagnostic mode. So, I suggest to report that
"-fno-sanitize-trap=cfi-foobar" is incompatible with a given target
toolchain.

Test Plan: regression test suite

Reviewers: pcc

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D10751

llvm-svn: 240716

1 files changed, 17 insertions, 1 deletions

diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 14c37025eb3..e203aac582a 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -26,6 +26,7 @@ using namespace llvm::opt;
 
 enum : SanitizerMask {
   NeedsUbsanRt = Undefined | Integer | CFI,
+  NeedsUbsanCxxRt = Vptr | CFI,
   NotAllowedWithTrap = Vptr,
   RequiresPIE = Memory | DataFlow,
   NeedsUnwindTables = Address | Thread | Memory | DataFlow,
@@ -194,7 +195,7 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   SanitizerMask DiagnosedKinds = 0;  // All Kinds we have diagnosed up to now.
                                      // Used to deduplicate diagnostics.
   SanitizerMask Kinds = 0;
-  SanitizerMask Supported = setGroupBits(TC.getSupportedSanitizers());
+  const SanitizerMask Supported = setGroupBits(TC.getSupportedSanitizers());
   ToolChain::RTTIMode RTTIMode = TC.getRTTIMode();
 
   const Driver &D = TC.getDriver();
@@ -282,6 +283,21 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
         << lastArgumentForMask(D, Args, Kinds & NeedsLTO) << "-flto";
   }
 
+  // Report error if there are non-trapping sanitizers that require
+  // c++abi-specific  parts of UBSan runtime, and they are not provided by the
+  // toolchain. We don't have a good way to check the latter, so we just
+  // check if the toolchan supports vptr.
+  if (~Supported & Vptr) {
+    if (SanitizerMask KindsToDiagnose =
+            Kinds & ~TrappingKinds & NeedsUbsanCxxRt) {
+      SanitizerSet S;
+      S.Mask = KindsToDiagnose;
+      D.Diag(diag::err_drv_unsupported_opt_for_target)
+          << ("-fno-sanitize-trap=" + toString(S)) << TC.getTriple().str();
+      Kinds &= ~KindsToDiagnose;
+    }
+  }
+
   // Warn about incompatible groups of sanitizers.
   std::pair<SanitizerMask, SanitizerMask> IncompatibleGroups[] = {
       std::make_pair(Address, Thread), std::make_pair(Address, Memory),