SafeStack: Disable Darwin support

[vlad.tsyrklevich]

Summary

Darwin support does not appear to be used as evidenced by the fact that
the runtime has never supported non-trivial programs.

[kubamracek]

Doesn't this need any tests to be updated? Otherwise, LGTM.

[vlad.tsyrklevich]

In D50724#1199345, @kubamracek wrote:

Doesn't this need any tests to be updated? Otherwise, LGTM.

There were no Darwin-specific safestack driver tests. I ran check-clang just to make sure and it passes.

[pcc]

LGTM

lib/Driver/ToolChains/Darwin.cpp

if (Args.hasArg(options::OPT_ObjC) || Args.hasArg(options::OPT_ObjCXX))
     CmdArgs.push_back("-ObjC");
 
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles))
     getMachOToolChain().addStartObjectFileArgs(Args, CmdArgs);
 
-  // SafeStack requires its own runtime libraries
-  // These libraries should be linked first, to make sure the
-  // __safestack_init constructor executes before everything else
-  if (getToolChain().getSanitizerArgs().needsSafeStackRt()) {
-    getMachOToolChain().AddLinkRuntimeLib(Args, CmdArgs,
-                                          "libclang_rt.safestack_osx.a",
-                                          toolchains::Darwin::RLO_AlwaysLink);
-  }
-
   Args.AddAllArgs(CmdArgs, options::OPT_L);
 
   AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs, JA);
   // Build the input file for -filelist (list of linker input files) in case we
   // need it later
   for (const auto &II : Inputs) {
     if (!II.isFilename()) {
       // This is a linker input argument.
SanitizerMask Darwin::getSupportedSanitizers() const {
   Res |= SanitizerKind::Address;
   Res |= SanitizerKind::Leak;
   Res |= SanitizerKind::Fuzzer;
   Res |= SanitizerKind::FuzzerNoLink;
   Res |= SanitizerKind::Function;
   if (isTargetMacOS()) {
     if (!isMacosxVersionLT(10, 9))
       Res |= SanitizerKind::Vptr;
-    Res |= SanitizerKind::SafeStack;
     if (IsX86_64)
       Res |= SanitizerKind::Thread;
   } else if (isTargetIOSSimulator() || isTargetTvOSSimulator()) {
     if (IsX86_64)
       Res |= SanitizerKind::Thread;
   }
   return Res;
 }
 
 void Darwin::printVerboseInfo(raw_ostream &OS) const {
   CudaInstallation.print(OS);
 }