[PATCH] Introduce -fsanitize-trap= flag.

[Alexey Samsonov]

I'm mostly happy with this patch. Accepting it, so that you can land it without yet another round of review, but please consider addressing the comments below.

Thank you for doing this!


================
Comment at: lib/Driver/SanitizerArgs.cpp:147
@@ +146,3 @@
+      Add &= ~TrapRemove;
+      if ((Add & ~TrappingSupportedWithGroups) != 0) {
+        SanitizerSet S;
----------------
  if (SanitizerMask InvalidValues = Add & ~TrappingSupportedWithGroups) {
    SanitizerSet S;
    S.Mask = InvalidValues;
    //....
  }

================
Comment at: lib/Driver/SanitizerArgs.cpp:165
@@ +164,3 @@
+      Arg->claim();
+      TrapRemove |= Undefined | UndefinedGroup;
+    }
----------------
  TrapRemove |= expandSanitizerGroups(UndefinedGroup);

================
Comment at: lib/Driver/SanitizerArgs.cpp:239
@@ +238,3 @@
+      SanitizerMask KindsToDiagnose = Add & NotSupported & ~DiagnosedKinds;
+      if (KindsToDiagnose & Vptr) {
+        D.Diag(diag::err_drv_argument_not_allowed_with)
----------------
I don't think this is right. Suppose `-fsanitize=vptr` is not supported on target foo (by corresponding toolchain). Then
  clang -target foo -fsanitize=vptr a.cc
would produce confusing
  "-fsanitize=vptr" is not allowed with "-fsanitize-trap=undefined"

I think you would need separate clause for that
  if (SanitizerMask KindsToDiagnose = Add & TrappingKinds & NotAllowedWithTrap & ~DiagnosedKinds) {
    std::string Desc = describeSanitizeArg(*I, KindsToDiagnose);
    D.Diag(diag::err_drv_argument_not_allowed_with) << Desc << lastTrapArgumentForMask(KindsToDiagnose);
    DiagnosedKinds |= KindsToDiagnose;
  }

http://reviews.llvm.org/D10464

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