Introduce -fsanitize-trap= flag.

This flag controls whether a given sanitizer traps upon detecting
an error. It currently only supports UBSan. The existing flag
-fsanitize-undefined-trap-on-error has been made an alias of
-fsanitize-trap=undefined.

This change also cleans up some awkward behavior around the combination
of -fsanitize-trap=undefined and -fsanitize=undefined. Previously we
would reject command lines containing the combination of these two flags,
as -fsanitize=vptr is not compatible with trapping. This required the
creation of -fsanitize=undefined-trap, which excluded -fsanitize=vptr
(and -fsanitize=function, but this seems like an oversight).

Now, -fsanitize=undefined is an alias for -fsanitize=undefined-trap,
and if -fsanitize-trap=undefined is specified, we treat -fsanitize=vptr
as an "unsupported" flag, which means that we error out if the flag is
specified explicitly, but implicitly disable it if the flag was implied
by -fsanitize=undefined.

Differential Revision: http://reviews.llvm.org/D10464

llvm-svn: 240105

clang/docs/UsersManual.rst

@@ -970,12 +970,9 @@ are listed below.
       includes all of the checks listed below other than
       ``unsigned-integer-overflow``.
 
-   -  ``-fsanitize=undefined-trap``: This includes all sanitizers
-      included by ``-fsanitize=undefined``, except those that require
-      runtime support. This group of sanitizers is intended to be
-      used in conjunction with the ``-fsanitize-undefined-trap-on-error``
-      flag. This includes all of the checks listed below other than
-      ``unsigned-integer-overflow`` and ``vptr``.
+   -  ``-fsanitize=undefined-trap``: This is a deprecated alias for
+      ``-fsanitize=undefined``.
+
    -  ``-fsanitize=dataflow``: :doc:`DataFlowSanitizer`, a general data
       flow analysis.
    -  ``-fsanitize=cfi``: :doc:`control flow integrity <ControlFlowIntegrity>`
@@ -1069,15 +1066,6 @@ are listed below.
       through. This mode may use extra memory in programs that copy
       uninitialized memory a lot.
 
-   Extra features of UndefinedBehaviorSanitizer:
-
-   -  ``-fsanitize-undefined-trap-on-error``: Causes traps to be emitted
-      rather than calls to runtime libraries when a problem is detected.
-      This option is intended for use in cases where the sanitizer runtime
-      cannot be used (for instance, when building libc or a kernel module).
-      This is only compatible with the sanitizers in the ``undefined-trap``
-      group.
-
    The ``-fsanitize=`` argument must also be provided when linking, in
    order to link to the appropriate runtime library. When using
    ``-fsanitize=vptr`` (or a group that includes it, such as
@@ -1101,11 +1089,39 @@ are listed below.
    sanitizers (e.g. :doc:`AddressSanitizer`) may not support recovery,
    and always crash the program after the issue is detected.
 
+   Note that the ``-fsanitize-trap`` flag has precedence over this flag.
+   This means that if a check has been configured to trap elsewhere on the
+   command line, or if the check traps by default, this flag will not have
+   any effect unless that sanitizer's trapping behavior is disabled with
+   ``-fno-sanitize-trap``.
+
+   For example, if a command line contains the flags ``-fsanitize=undefined
+   -fsanitize-trap=undefined``, the flag ``-fsanitize-recover=alignment``
+   will have no effect on its own; it will need to be accompanied by
+   ``-fno-sanitize-trap=alignment``.
+
+**-f[no-]sanitize-trap=check1,check2,...**
+
+   Controls which checks enabled by the ``-fsanitize=`` flag trap. This
+   option is intended for use in cases where the sanitizer runtime cannot
+   be used (for instance, when building libc or a kernel module), or where
+   the binary size increase caused by the sanitizer runtime is a concern.
+
+   This flag is only compatible with ``local-bounds``,
+   ``unsigned-integer-overflow`` and sanitizers in the ``undefined``
+   group other than ``vptr``. If this flag is supplied together with
+   ``-fsanitize=undefined``, the ``vptr`` sanitizer will be implicitly
+   disabled.
+
 **-f[no-]sanitize-coverage=[type,features,...]**
 
    Enable simple code coverage in addition to certain sanitizers.
    See :doc:`SanitizerCoverage` for more details.
 
+.. option:: -fsanitize-undefined-trap-on-error
+
+   Deprecated alias for ``-fsanitize-trap=undefined``.
+
 .. option:: -fno-assume-sane-operator-new
 
    Don't assume that the C++'s new operator is sane.

clang/include/clang/Basic/Sanitizers.def

@@ -90,18 +90,17 @@ SANITIZER_GROUP("cfi", CFI,
 // Safe Stack
 SANITIZER("safe-stack", SafeStack)
 
-// -fsanitize=undefined-trap includes sanitizers from -fsanitize=undefined
-// that can be used without runtime support, generally by providing extra
-// -fsanitize-undefined-trap-on-error flag.
-SANITIZER_GROUP("undefined-trap", UndefinedTrap,
+// -fsanitize=undefined includes all the sanitizers which have low overhead, no
+// ABI or address space layout implications, and only catch undefined behavior.
+SANITIZER_GROUP("undefined", Undefined,
                 Alignment | Bool | ArrayBounds | Enum | FloatCastOverflow |
                     FloatDivideByZero | IntegerDivideByZero | NonnullAttribute |
                     Null | ObjectSize | Return | ReturnsNonnullAttribute |
-                    Shift | SignedIntegerOverflow | Unreachable | VLABound)
+                    Shift | SignedIntegerOverflow | Unreachable | VLABound |
+                    Function | Vptr)
 
-// -fsanitize=undefined includes all the sanitizers which have low overhead, no
-// ABI or address space layout implications, and only catch undefined behavior.
-SANITIZER_GROUP("undefined", Undefined, UndefinedTrap | Function | Vptr)
+// -fsanitize=undefined-trap is an alias for -fsanitize=undefined.
+SANITIZER_GROUP("undefined-trap", UndefinedTrap, Undefined)
 
 SANITIZER_GROUP("integer", Integer,
                 SignedIntegerOverflow | UnsignedIntegerOverflow | Shift |

clang/include/clang/Driver/Options.td

@@ -561,8 +561,13 @@ def fno_sanitize_recover_EQ
     : CommaJoined<["-"], "fno-sanitize-recover=">,
       Group<f_clang_Group>,
       HelpText<"Disable recovery for specified sanitizers">;
+def fsanitize_trap_EQ : CommaJoined<["-"], "fsanitize-trap=">, Group<f_clang_Group>,
+                        Flags<[CC1Option, CoreOption]>,
+                        HelpText<"Enable trapping for specified sanitizers">;
+def fno_sanitize_trap_EQ : CommaJoined<["-"], "fno-sanitize-trap=">, Group<f_clang_Group>,
+                           HelpText<"Disable trapping for specified sanitizers">;
 def fsanitize_undefined_trap_on_error : Flag<["-"], "fsanitize-undefined-trap-on-error">,
-                                        Group<f_clang_Group>, Flags<[CC1Option]>;
+                                        Group<f_clang_Group>;
 def fno_sanitize_undefined_trap_on_error : Flag<["-"], "fno-sanitize-undefined-trap-on-error">,
                                            Group<f_clang_Group>;
 def fsanitize_link_cxx_runtime : Flag<["-"], "fsanitize-link-c++-runtime">,

clang/include/clang/Driver/SanitizerArgs.h

@@ -23,13 +23,13 @@ class ToolChain;
 class SanitizerArgs {
   SanitizerSet Sanitizers;
   SanitizerSet RecoverableSanitizers;
+  SanitizerSet TrapSanitizers;
 
   std::vector<std::string> BlacklistFiles;
   int CoverageFeatures;
   int MsanTrackOrigins;
   int AsanFieldPadding;
   bool AsanZeroBaseShadow;
-  bool UbsanTrapOnError;
   bool AsanSharedRuntime;
   bool LinkCXXRuntimes;
 

clang/include/clang/Frontend/CodeGenOptions.def

@@ -120,8 +120,6 @@ CODEGENOPT(SanitizeCoverageTraceCmp, 1, 0) ///< Enable cmp instruction tracing
                                            ///< in sanitizer coverage.
 CODEGENOPT(SanitizeCoverage8bitCounters, 1, 0) ///< Use 8-bit frequency counters
                                                ///< in sanitizer coverage.
-CODEGENOPT(SanitizeUndefinedTrapOnError, 1, 0) ///< Set on
-                                               /// -fsanitize-undefined-trap-on-error
 CODEGENOPT(SimplifyLibCalls  , 1, 1) ///< Set when -fbuiltin is enabled.
 CODEGENOPT(SoftFloat         , 1, 0) ///< -soft-float.
 CODEGENOPT(StrictEnums       , 1, 0) ///< Optimize based on strict enum definition.

clang/include/clang/Frontend/CodeGenOptions.h

@@ -197,6 +197,9 @@ class CodeGenOptions : public CodeGenOptionsBase {
   /// continued when possible).
   SanitizerSet SanitizeRecover;
 
+  /// Set of sanitizer checks that trap rather than diagnose.
+  SanitizerSet SanitizeTrap;
+
 public:
   // Define accessors/mutators for code generation options of enumeration type.
 #define CODEGENOPT(Name, Bits, Default)

clang/lib/CodeGen/CGExpr.cpp

@@ -2300,15 +2300,24 @@ void CodeGenFunction::EmitCheck(
 
   llvm::Value *FatalCond = nullptr;
   llvm::Value *RecoverableCond = nullptr;
+  llvm::Value *TrapCond = nullptr;
   for (int i = 0, n = Checked.size(); i < n; ++i) {
     llvm::Value *Check = Checked[i].first;
+    // -fsanitize-trap= overrides -fsanitize-recover=.
     llvm::Value *&Cond =
-        CGM.getCodeGenOpts().SanitizeRecover.has(Checked[i].second)
-            ? RecoverableCond
-            : FatalCond;
+        CGM.getCodeGenOpts().SanitizeTrap.has(Checked[i].second)
+            ? TrapCond
+            : CGM.getCodeGenOpts().SanitizeRecover.has(Checked[i].second)
+                  ? RecoverableCond
+                  : FatalCond;
     Cond = Cond ? Builder.CreateAnd(Cond, Check) : Check;
   }
 
+  if (TrapCond)
+    EmitTrapCheck(TrapCond);
+  if (!FatalCond && !RecoverableCond)
+    return;
+
   llvm::Value *JointCond;
   if (FatalCond && RecoverableCond)
     JointCond = Builder.CreateAnd(FatalCond, RecoverableCond);
@@ -2326,15 +2335,6 @@ void CodeGenFunction::EmitCheck(
   }
 #endif
 
-  if (CGM.getCodeGenOpts().SanitizeUndefinedTrapOnError) {
-    assert(RecoverKind != CheckRecoverableKind::AlwaysRecoverable &&
-           "Runtime call required for AlwaysRecoverable kind!");
-    // Assume that -fsanitize-undefined-trap-on-error overrides
-    // -fsanitize-recover= options, as we can only print meaningful error
-    // message and recover if we have a runtime support.
-    return EmitTrapCheck(JointCond);
-  }
-
   llvm::BasicBlock *Cont = createBasicBlock("cont");
   llvm::BasicBlock *Handlers = createBasicBlock("handler." + CheckName);
   llvm::Instruction *Branch = Builder.CreateCondBr(JointCond, Cont, Handlers);

clang/lib/Driver/SanitizerArgs.cpp

@@ -34,6 +34,8 @@ enum : SanitizerMask {
   Unrecoverable = Address | Unreachable | Return,
   LegacyFsanitizeRecoverMask = Undefined | Integer,
   NeedsLTO = CFI,
+  TrappingSupported =
+      (Undefined & ~Vptr) | UnsignedIntegerOverflow | LocalBounds,
 };
 
 enum CoverageFeature {
@@ -116,8 +118,59 @@ static bool getDefaultBlacklist(const Driver &D, SanitizerMask Kinds,
   return false;
 }
 
+/// Sets group bits for every group that has at least one representative already
+/// enabled in \p Kinds.
+static SanitizerMask setGroupBits(SanitizerMask Kinds) {
+#define SANITIZER(NAME, ID)
+#define SANITIZER_GROUP(NAME, ID, ALIAS)                                       \
+  if (Kinds & SanitizerKind::ID)                                               \
+    Kinds |= SanitizerKind::ID##Group;
+#include "clang/Basic/Sanitizers.def"
+  return Kinds;
+}
+
+static SanitizerMask parseSanitizeTrapArgs(const Driver &D,
+                                           const llvm::opt::ArgList &Args) {
+  SanitizerMask TrapRemove = 0; // During the loop below, the accumulated set of
+                                // sanitizers disabled by the current sanitizer
+                                // argument or any argument after it.
+  SanitizerMask TrappingKinds = 0;
+  SanitizerMask TrappingSupportedWithGroups = setGroupBits(TrappingSupported);
+
+  for (ArgList::const_reverse_iterator I = Args.rbegin(), E = Args.rend();
+       I != E; ++I) {
+    const auto *Arg = *I;
+    if (Arg->getOption().matches(options::OPT_fsanitize_trap_EQ)) {
+      Arg->claim();
+      SanitizerMask Add = parseArgValues(D, Arg, true);
+      Add &= ~TrapRemove;
+      if (SanitizerMask InvalidValues = Add & ~TrappingSupportedWithGroups) {
+        SanitizerSet S;
+        S.Mask = InvalidValues;
+        D.Diag(diag::err_drv_unsupported_option_argument) << "-fsanitize-trap"
+                                                          << toString(S);
+      }
+      TrappingKinds |= expandSanitizerGroups(Add) & ~TrapRemove;
+    } else if (Arg->getOption().matches(options::OPT_fno_sanitize_trap_EQ)) {
+      Arg->claim();
+      TrapRemove |= expandSanitizerGroups(parseArgValues(D, Arg, true));
+    } else if (Arg->getOption().matches(
+                   options::OPT_fsanitize_undefined_trap_on_error)) {
+      Arg->claim();
+      TrappingKinds |=
+          expandSanitizerGroups(UndefinedGroup & ~TrapRemove) & ~TrapRemove;
+    } else if (Arg->getOption().matches(
+                   options::OPT_fno_sanitize_undefined_trap_on_error)) {
+      Arg->claim();
+      TrapRemove |= expandSanitizerGroups(UndefinedGroup);
+    }
+  }
+
+  return TrappingKinds;
+}
+
 bool SanitizerArgs::needsUbsanRt() const {
-  return !UbsanTrapOnError && (Sanitizers.Mask & NeedsUbsanRt) &&
+  return (Sanitizers.Mask & NeedsUbsanRt & ~TrapSanitizers.Mask) &&
          !Sanitizers.has(Address) &&
          !Sanitizers.has(Memory) &&
          !Sanitizers.has(Thread);
@@ -138,12 +191,12 @@ bool SanitizerArgs::needsLTO() const {
 void SanitizerArgs::clear() {
   Sanitizers.clear();
   RecoverableSanitizers.clear();
+  TrapSanitizers.clear();
   BlacklistFiles.clear();
   CoverageFeatures = 0;
   MsanTrackOrigins = 0;
   AsanFieldPadding = 0;
   AsanZeroBaseShadow = false;
-  UbsanTrapOnError = false;
   AsanSharedRuntime = false;
   LinkCXXRuntimes = false;
 }
@@ -166,6 +219,9 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   ToolChain::RTTIMode RTTIMode = TC.getRTTIMode();
 
   const Driver &D = TC.getDriver();
+  SanitizerMask TrappingKinds = parseSanitizeTrapArgs(D, Args);
+  NotSupported |= TrappingKinds & NotAllowedWithTrap;
+
   for (ArgList::const_reverse_iterator I = Args.rbegin(), E = Args.rend();
        I != E; ++I) {
     const auto *Arg = *I;
@@ -180,7 +236,14 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
       // sanitizers in Add are those which have been explicitly enabled.
       // Diagnose them.
       if (SanitizerMask KindsToDiagnose =
-              Add & NotSupported & ~DiagnosedKinds) {
+              Add & TrappingKinds & NotAllowedWithTrap & ~DiagnosedKinds) {
+        std::string Desc = describeSanitizeArg(*I, KindsToDiagnose);
+        D.Diag(diag::err_drv_argument_not_allowed_with)
+            << Desc << "-fsanitize-trap=undefined";
+        DiagnosedKinds |= KindsToDiagnose;
+        Add &= ~KindsToDiagnose;
+      }
+      if (SanitizerMask KindsToDiagnose = Add & NotSupported & ~DiagnosedKinds) {
         // Only diagnose the new kinds.
         std::string Desc = describeSanitizeArg(*I, KindsToDiagnose);
         D.Diag(diag::err_drv_unsupported_opt_for_target)
@@ -234,17 +297,6 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
     Kinds &= ~Vptr;
   }
 
-  // Warn about undefined sanitizer options that require runtime support.
-  UbsanTrapOnError =
-    Args.hasFlag(options::OPT_fsanitize_undefined_trap_on_error,
-                 options::OPT_fno_sanitize_undefined_trap_on_error, false);
-  if (UbsanTrapOnError && (Kinds & NotAllowedWithTrap)) {
-    D.Diag(clang::diag::err_drv_argument_not_allowed_with)
-        << lastArgumentForMask(D, Args, NotAllowedWithTrap)
-        << "-fsanitize-undefined-trap-on-error";
-    Kinds &= ~NotAllowedWithTrap;
-  }
-
   // Warn about incompatible groups of sanitizers.
   std::pair<SanitizerMask, SanitizerMask> IncompatibleGroups[] = {
       std::make_pair(Address, Thread), std::make_pair(Address, Memory),
@@ -305,6 +357,8 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   RecoverableKinds &= Kinds;
   RecoverableKinds &= ~Unrecoverable;
 
+  TrappingKinds &= Kinds;
+
   // Setup blacklist files.
   // Add default blacklist from resource directory.
   {
@@ -460,6 +514,7 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   // Finally, initialize the set of available and recoverable sanitizers.
   Sanitizers.Mask |= Kinds;
   RecoverableSanitizers.Mask |= RecoverableKinds;
+  TrapSanitizers.Mask |= TrappingKinds;
 }
 
 static std::string toString(const clang::SanitizerSet &Sanitizers) {
@@ -484,8 +539,9 @@ void SanitizerArgs::addArgs(const llvm::opt::ArgList &Args,
     CmdArgs.push_back(Args.MakeArgString("-fsanitize-recover=" +
                                          toString(RecoverableSanitizers)));
 
-  if (UbsanTrapOnError)
-    CmdArgs.push_back("-fsanitize-undefined-trap-on-error");
+  if (!TrapSanitizers.empty())
+    CmdArgs.push_back(
+        Args.MakeArgString("-fsanitize-trap=" + toString(TrapSanitizers)));
 
   for (const auto &BLPath : BlacklistFiles) {
     SmallString<64> BlacklistOpt("-fsanitize-blacklist=");
@@ -528,7 +584,9 @@ SanitizerMask parseArgValues(const Driver &D, const llvm::opt::Arg *A,
   assert((A->getOption().matches(options::OPT_fsanitize_EQ) ||
           A->getOption().matches(options::OPT_fno_sanitize_EQ) ||
           A->getOption().matches(options::OPT_fsanitize_recover_EQ) ||
-          A->getOption().matches(options::OPT_fno_sanitize_recover_EQ)) &&
+          A->getOption().matches(options::OPT_fno_sanitize_recover_EQ) ||
+          A->getOption().matches(options::OPT_fsanitize_trap_EQ) ||
+          A->getOption().matches(options::OPT_fno_sanitize_trap_EQ)) &&
          "Invalid argument in parseArgValues!");
   SanitizerMask Kinds = 0;
   for (int i = 0, n = A->getNumValues(); i != n; ++i) {

clang/lib/Frontend/CompilerInvocation.cpp

@@ -555,8 +555,6 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
       Args.hasArg(OPT_fsanitize_coverage_8bit_counters);
   Opts.SanitizeMemoryTrackOrigins =
       getLastArgIntValue(Args, OPT_fsanitize_memory_track_origins_EQ, 0, Diags);
-  Opts.SanitizeUndefinedTrapOnError =
-      Args.hasArg(OPT_fsanitize_undefined_trap_on_error);
   Opts.SSPBufferSize =
       getLastArgIntValue(Args, OPT_stack_protector_buffer_size, 8, Diags);
   Opts.StackRealignment = Args.hasArg(OPT_mstackrealign);
@@ -666,6 +664,9 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   parseSanitizerKinds("-fsanitize-recover=",
                       Args.getAllArgValues(OPT_fsanitize_recover_EQ), Diags,
                       Opts.SanitizeRecover);
+  parseSanitizerKinds("-fsanitize-trap=",
+                      Args.getAllArgValues(OPT_fsanitize_trap_EQ), Diags,
+                      Opts.SanitizeTrap);
 
   Opts.CudaGpuBinaryFileNames =
       Args.getAllArgValues(OPT_fcuda_include_gpubinary);

clang/test/CodeGen/bounds-checking.c

@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -fsanitize=local-bounds -emit-llvm -triple x86_64-apple-darwin10 %s -o - | FileCheck %s
-// RUN: %clang_cc1 -fsanitize=array-bounds -O -fsanitize-undefined-trap-on-error -emit-llvm -triple x86_64-apple-darwin10 -DNO_DYNAMIC %s -o - | FileCheck %s
+// RUN: %clang_cc1 -fsanitize=array-bounds -O -fsanitize-trap=array-bounds -emit-llvm -triple x86_64-apple-darwin10 -DNO_DYNAMIC %s -o - | FileCheck %s
 
 // CHECK-LABEL: @f
 double f(int b, int i) {

clang/test/CodeGen/catch-undef-behavior.c

@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -fsanitize=alignment,null,object-size,shift-base,shift-exponent,return,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize-recover=alignment,null,object-size,shift-base,shift-exponent,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-UBSAN
-// RUN: %clang_cc1 -fsanitize-undefined-trap-on-error -fsanitize=alignment,null,object-size,shift-base,shift-exponent,return,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize-recover=alignment,null,object-size,shift-base,shift-exponent,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-TRAP
+// RUN: %clang_cc1 -fsanitize-trap=alignment,null,object-size,shift-base,shift-exponent,return,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize-recover=alignment,null,object-size,shift-base,shift-exponent,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize=alignment,null,object-size,shift-base,shift-exponent,return,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize-recover=alignment,null,object-size,shift-base,shift-exponent,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-TRAP
 // RUN: %clang_cc1 -fsanitize=null -fsanitize-recover=null -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK-NULL
 // RUN: %clang_cc1 -fsanitize=signed-integer-overflow -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK-OVERFLOW
 // REQUIRES: asserts