[UBSan] Embed UBSan into ASan runtime (Clang part).

[samsonov]

Summary

Change the way we use ASan and UBSan together. Instead of keeping two
separate runtimes (libclang_rt.asan and libclang_rt.ubsan), embed UBSan
into ASan and get rid of libclang_rt.ubsan. If UBSan is not supported on
a platform, all UBSan sources are just compiled into dummy empty object
files. UBSan initialization code (e.g. flag parsing) is directly called
from ASan initialization, so we are able to enforce correct
initialization order.

This mirrors the approach we already use for ASan+LSan.

This change doesn't modify the way we use standalone UBSan.

lib/Driver/SanitizerArgs.cpp

if (BlacklistFile) {
     llvm::sys::path::append(Path, BlacklistFile);
     BLPath = Path.str();
     return true;
   }
   return false;
 }
 
 bool SanitizerArgs::needsUbsanRt() const {
-  return !UbsanTrapOnError && hasOneOf(Sanitizers, NeedsUbsanRt);
+  return !UbsanTrapOnError && hasOneOf(Sanitizers, NeedsUbsanRt) &&
+         !Sanitizers.has(SanitizerKind::Address);
 }
 
 bool SanitizerArgs::requiresPIE() const {
   return AsanZeroBaseShadow || hasOneOf(Sanitizers, RequiresPIE);
 }
 
 bool SanitizerArgs::needsUnwindTables() const {
   return hasOneOf(Sanitizers, NeedsUnwindTables);

lib/Driver/ToolChains.cpp

if (!Args.hasArg(options::OPT_dynamiclib) &&
     AddCXXStdlibLibArgs(Args, CmdArgs);
   }
   assert(isTargetMacOS() || isTargetIOSSimulator());
   StringRef OS = isTargetMacOS() ? "osx" : "iossim";
   AddLinkRuntimeLib(Args, CmdArgs, (Twine("libclang_rt.") + Sanitizer + "_" +
                                     OS + "_dynamic.dylib").str(),
                     /*AlwaysLink*/ true, /*IsEmbedded*/ false,
                     /*AddRPath*/ true);
+  // Add explicit dependcy on -lc++abi, as -lc++ doesn't re-export
+  // all RTTI-related symbols that UBSan uses.
+  CmdArgs.push_back("-lc++abi");
 }
 
 void DarwinClang::AddLinkRuntimeLibArgs(const ArgList &Args,
                                         ArgStringList &CmdArgs) const {
   // Darwin only supports the compiler-rt based runtime libraries.
   switch (GetRuntimeLibType(Args)) {
   case ToolChain::RLT_CompilerRT:
     break;
void DarwinClang::AddLinkRuntimeLibArgs(const ArgList &Args,
 
   if (Sanitize.needsUbsanRt()) {
     if (!isTargetMacOS() && !isTargetIOSSimulator()) {
       // FIXME: Move this check to SanitizerArgs::filterUnsupportedKinds.
       getDriver().Diag(diag::err_drv_clang_unsupported_per_platform)
           << "-fsanitize=undefined";
     } else {
       AddLinkSanitizerLibArgs(Args, CmdArgs, "ubsan");
-      // Add explicit dependcy on -lc++abi, as -lc++ doesn't re-export
-      // all RTTI-related symbols that UBSan uses.
-      CmdArgs.push_back("-lc++abi");
     }
   }
 
   // Otherwise link libSystem, then the dynamic runtime library, and finally any
   // target specific static runtime library.
   CmdArgs.push_back("-lSystem");
 
   // Select the dynamic runtime library and the target specific static library.

lib/Driver/Tools.cpp

collectSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
   if (SanArgs.needsDfsanRt())
     StaticRuntimes.push_back("dfsan");
   if (SanArgs.needsLsanRt())
     StaticRuntimes.push_back("lsan");
   if (SanArgs.needsMsanRt())
     StaticRuntimes.push_back("msan");
   if (SanArgs.needsTsanRt())
     StaticRuntimes.push_back("tsan");
-  // WARNING: UBSan should always go last.
   if (SanArgs.needsUbsanRt()) {
-    // Check if UBSan is combined with another sanitizers.
-    if (StaticRuntimes.empty()) {
-      StaticRuntimes.push_back("ubsan_standalone");
-      if (SanArgs.linkCXXRuntimes())
-        StaticRuntimes.push_back("ubsan_standalone_cxx");
-    } else {
-      StaticRuntimes.push_back("ubsan");
-      if (SanArgs.linkCXXRuntimes())
-        StaticRuntimes.push_back("ubsan_cxx");
-    }
   }
 }
 
 // Should be called before we add system libraries (C++ ABI, libstdc++/libc++,
 // C runtime, etc). Returns true if sanitizer system deps need to be linked in.
 static bool addSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
                                  ArgStringList &CmdArgs) {
   SmallVector<StringRef, 4> SharedRuntimes, StaticRuntimes,

test/Driver/sanitizer-ld.c

 // CHECK-UBSAN-LINUX-CXX: "-lpthread"
 
 // RUN: %clang -fsanitize=address,undefined %s -### -o %t.o 2>&1 \
 // RUN:     -target i386-unknown-linux \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-ASAN-UBSAN-LINUX %s
 // CHECK-ASAN-UBSAN-LINUX: "{{.*}}ld{{(.exe)?}}"
 // CHECK-ASAN-UBSAN-LINUX: "-whole-archive" "{{.*}}libclang_rt.asan-i386.a" "-no-whole-archive"
-// CHECK-ASAN-UBSAN-LINUX: "-whole-archive" "{{.*}}libclang_rt.ubsan-i386.a" "-no-whole-archive"
-// CHECK-ASAN-UBSAN-LINUX-NOT: libclang_rt.ubsan_cxx
+// CHECK-ASAN-UBSAN-LINUX-NOT: libclang_rt.ubsan
 // CHECK-ASAN-UBSAN-LINUX-NOT: "-lstdc++"
 // CHECK-ASAN-UBSAN-LINUX: "-lpthread"
 
 // RUN: %clangxx -fsanitize=address,undefined %s -### -o %t.o 2>&1 \
 // RUN:     -target i386-unknown-linux \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-ASAN-UBSAN-LINUX-CXX %s
 // CHECK-ASAN-UBSAN-LINUX-CXX: "{{.*}}ld{{(.exe)?}}"
 // CHECK-ASAN-UBSAN-LINUX-CXX: "-whole-archive" "{{.*}}libclang_rt.asan-i386.a" "-no-whole-archive"
-// CHECK-ASAN-UBSAN-LINUX-CXX: "-whole-archive" "{{.*}}libclang_rt.ubsan-i386.a" "-no-whole-archive"
-// CHECK-ASAN-UBSAN-LINUX-CXX: "-whole-archive" "{{.*}}libclang_rt.ubsan_cxx-i386.a" "-no-whole-archive"
+// CHECK-ASAN-UBSAN-LINUX-CXX: "-whole-archive" "{{.*}}libclang_rt.asan_cxx-i386.a" "-no-whole-archive"
+// CHECK-ASAN-UBSAN-LINUX-CXX-NOT: libclang_rt.ubsan
 // CHECK-ASAN-UBSAN-LINUX-CXX: "-lstdc++"
 // CHECK-ASAN-UBSAN-LINUX-CXX: "-lpthread"
 
 // RUN: %clang -fsanitize=undefined %s -### -o %t.o 2>&1 \
 // RUN:     -target i386-unknown-linux \
 // RUN:     -resource-dir=%S/Inputs/resource_dir \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:     -shared \