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

[Alexey Samsonov]

Hi pcc,

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.

http://reviews.llvm.org/D10751

Files:
  lib/Driver/SanitizerArgs.cpp
  test/Driver/fsanitize.c

Index: lib/Driver/SanitizerArgs.cpp
===================================================================
--- lib/Driver/SanitizerArgs.cpp
+++ lib/Driver/SanitizerArgs.cpp
@@ -26,6 +26,7 @@
 
 enum : SanitizerMask {
   NeedsUbsanRt = Undefined | Integer | CFI,
+  NeedsUbsanCxxRt = Vptr | CFI,
   NotAllowedWithTrap = Vptr,
   RequiresPIE = Memory | DataFlow,
   NeedsUnwindTables = Address | Thread | Memory | DataFlow,
@@ -194,7 +195,7 @@
   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 @@
         << 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),
Index: test/Driver/fsanitize.c
===================================================================
--- test/Driver/fsanitize.c
+++ test/Driver/fsanitize.c
@@ -234,6 +234,9 @@
 // RUN: %clang -target x86_64-linux-gnu -fsanitize-trap=address -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-TRAP
 // CHECK-ASAN-TRAP: error: unsupported argument 'address' to option '-fsanitize-trap'
 
+// RUN: %clang -target x86_64-apple-darwin10 -mmacosx-version-min=10.7 -flto -fsanitize=cfi-vcall -fno-sanitize-trap=cfi -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-NOTRAP-OLD-MACOS
+// CHECK-CFI-NOTRAP-OLD-MACOS: error: unsupported option '-fno-sanitize-trap=cfi-vcall' for target 'x86_64-apple-darwin10'
+
 // RUN: %clang_cl -fsanitize=address -c -MDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -MTd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -LDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL

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