[asan] Default to -fsanitize-address-use-odr-indicator for non-Windows

[MaskRay]

Summary

This enables odr indicators on all platforms and private aliases on non-Windows.
Note that GCC also uses private aliases: this fixes bogus
The following global variable is not properly aligned. errors for interposed global variables

Fix https://github.com/google/sanitizers/issues/398
Fix https://github.com/google/sanitizers/issues/1017
Fix https://github.com/llvm/llvm-project/issues/36893 (we can restore D46665)

Global variables of non-hasExactDefinition() linkages (i.e.
linkonce/linkonce_odr/weak/weak_odr/common/external_weak) are not instrumented.
If an instrumented variable gets interposed to an uninstrumented variable due to
symbol interposition (e.g. in issue 36893, _ZTS1A in foo.so is resolved to _ZTS1A in
the executable), there may be a bogus error.

With private aliases, the register code will not resolve to a definition in
another module, and thus prevent the issue.

Cons: minor size increase. This is mainly due to extra __odr_asan_gen_* symbols.
(ELF) In addition, in relocatable files private aliases replace some relocations
referencing global symbols with .L symbols and may introduce some STT_SECTION symbols.

For lld, with -g0, the size increase is 0.07~0.09% for many configurations I
have tested: -O0, -O1, -O2, -O3, -O2 -ffunction-sections -fdata-sections
-Wl,--gc-sections. With -g1 or above, the size increase ratio will be even smaller.

This patch obsoletes D92078.

Don't migrate Windows for now: the static data member of a specialization
std::num_put<char>::id is a weak symbol, as well as its ODR indicator.
Unfortunately, link.exe (and lld without -lldmingw) generally doesn't support
duplicate weak definitions (weak symbols in different TUs likely pick different
defined external symbols and conflict).

[MaskRay]

exclude Windows for its weak symbol issue

[kstoimenov]

llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll

8

Remove extra space?

[vitalybuka]

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

777–782

It should be

UseOdrIndicator(ClUseOdrIndicator.getNumOccurrences() > 0 ? ClUseOdrIndicator : UseOdrIndicator),
ClUsePrivateAlias(ClUsePrivateAlias.getNumOccurrences() > 0 ? ClUsePrivateAlias : UseOdrIndicator),

My rule of thumb is Cl flags, which are mostly for testing, must be direct and do exactly what was asked, even if it's not useful, and they should override fronted parameters.

[MaskRay]

address comments

Thanks for the quick review:)

[sbc100]

At least for WebAssembly object files, it looks like the symbol table now contains (what look like) demangled symbols. e.g.:

$ llvm-nm /tmp/emscripten_temp/command_0.o 
00003ef5 D __odr_asan_gen__numargs
000041a6 D __odr_asan_gen__stdcmd<1068>::init
000041c3 D __odr_asan_gen__stdcmd<1069>::init
000041e0 D __odr_asan_gen__stdcmd<1070>::init
000041fd D __odr_asan_gen__stdcmd<1071>::init
0000421a D __odr_asan_gen__stdcmd<1073>::init
0000423f D __odr_asan_gen__stdcmd<1074>::init
0000425c D __odr_asan_gen__stdcmd<1075>::init
00004279 D __odr_asan_gen__stdcmd<1076>::init
0000429e D __odr_asan_gen__stdcmd<1077>::init
000042bc D __odr_asan_gen__stdcmd<1078>::init

Symbol names with colon in them currently cause issues with the emscripten compiler (when parsing the output of llvm-nm). If this is intentional we can look into re-working the parser, but I just wanted to check if this was indented behaviour? Are these characters allowed in symbol names?

[MaskRay]

In D137227#3908994, @sbc100 wrote:

At least for WebAssembly object files, it looks like the symbol table now contains (what look like) demangled symbols. e.g.:

$ llvm-nm /tmp/emscripten_temp/command_0.o 
00003ef5 D __odr_asan_gen__numargs
000041a6 D __odr_asan_gen__stdcmd<1068>::init
000041c3 D __odr_asan_gen__stdcmd<1069>::init
000041e0 D __odr_asan_gen__stdcmd<1070>::init
000041fd D __odr_asan_gen__stdcmd<1071>::init
0000421a D __odr_asan_gen__stdcmd<1073>::init
0000423f D __odr_asan_gen__stdcmd<1074>::init
0000425c D __odr_asan_gen__stdcmd<1075>::init
00004279 D __odr_asan_gen__stdcmd<1076>::init
0000429e D __odr_asan_gen__stdcmd<1077>::init
000042bc D __odr_asan_gen__stdcmd<1078>::init

Symbol names with colon in them currently cause issues with the emscripten compiler (when parsing the output of llvm-nm). If this is intensional we can look into re-working the parser, but I just wanted to check if this was indented behaviour? Are these character allows in symbol names?

The asan instrumentation just prepends __odr_asan_gen_ to the symbol name to form a new symbol name. For ELF every byte except \0 can be used in a symbol name, and this is totally fine.

I am unfamiliar with WebAssembly. Does the aforementioned parsing tool somehow skip printing _stdcmd<1068>::init symbols?

ModuleAddressSanitizer::shouldInstrumentGlobal encodes the candidate global variables.

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

777–782

Good catch. I agree with this analysis.

[sbc100]

The asan instrumentation just prepends __odr_asan_gen_ to the symbol name to form a new symbol name. For ELF every byte except \0 can be used in a symbol name, and this is totally fine.

I am unfamiliar with WebAssembly. Does the aforementioned parsing tool somehow skip printing _stdcmd<1068>::init symbols?

The parser was confused by the presence of a colon in the symbol names and generating an error. I created a patch that makes it a little more robust: https://github.com/emscripten-core/emscripten/pull/18152

So we have a fix for the proximate issue, but I just wanted to check if that new prepended symbol name was supposed to be the demanded C++ name (which it seem to be) rather than the mangled name?

This is the first time we've had these characters appearing in symbol names so I just wanted to flag that as relatively unprecedented (at least in terms of all the codebases that emscripten has been exposed to so far).

ModuleAddressSanitizer::shouldInstrumentGlobal encodes the candidate global variables.

[MaskRay]

In D137227#3909056, @sbc100 wrote:

The asan instrumentation just prepends __odr_asan_gen_ to the symbol name to form a new symbol name. For ELF every byte except \0 can be used in a symbol name, and this is totally fine.

I am unfamiliar with WebAssembly. Does the aforementioned parsing tool somehow skip printing _stdcmd<1068>::init symbols?

The parser was confused by the presence of a colon in the symbol names and generating an error. I created a patch that makes it a little more robust: https://github.com/emscripten-core/emscripten/pull/18152

So we have a fix for the proximate issue, but I just wanted to check if that new prepended symbol name was supposed to be the demanded C++ name (which it seem to be) rather than the mangled name?

I think so. The instrumentation is done at LLVM layer, not Clang layer. The LLVM layer code generally shouldn't know the different mangling schemes used by different language frontends.
For C++, we can get a mangled variable name with something like

template <typename T>
inline int var = 3;

int *x = &var<int>;

_Z3varIiE

My understanding is that all such symbols are in a COMDAT and have a linkonce_odr/weak_odr linkage: these symbols are skipped by ModuleAddressSanitizer::shouldInstrumentGlobal, so one will not see __odr_asan_gen__Z3varIiE. (And even if such a symbol name appears, it's not a big deal. Unable to demangle such non-interesting symbols is fine, IMHO.)
I do not know what the WebAssembly world does but if you can provide detail instructions for reproduce I am happy to take a look if needed.

This is the first time we've had these characters appearing in symbol names so I just wanted to flag that as relatively unprecedented (at least in terms of all the codebases that emscripten has been exposed to so far).

ModuleAddressSanitizer::shouldInstrumentGlobal encodes the candidate global variables.

clang/include/clang/Driver/Options.td

defm sanitize_address_poison_custom_array_cookie : BoolOption<"f", "sanitize-address-poison-custom-array-cookie",
   BothFlags<[], " poisoning array cookies when using custom operator new[] in AddressSanitizer">>,
   Group<f_clang_Group>;
 defm sanitize_address_globals_dead_stripping : BoolOption<"f", "sanitize-address-globals-dead-stripping",
   CodeGenOpts<"SanitizeAddressGlobalsDeadStripping">, DefaultFalse,
   PosFlag<SetTrue, [], "Enable linker dead stripping of globals in AddressSanitizer">,
   NegFlag<SetFalse, [], "Disable linker dead stripping of globals in AddressSanitizer">>,
   Group<f_clang_Group>;
 defm sanitize_address_use_odr_indicator : BoolOption<"f", "sanitize-address-use-odr-indicator",
-  CodeGenOpts<"SanitizeAddressUseOdrIndicator">, DefaultFalse,
+  CodeGenOpts<"SanitizeAddressUseOdrIndicator">, DefaultTrue,
   PosFlag<SetTrue, [], "Enable ODR indicator globals to avoid false ODR violation"
             " reports in partially sanitized programs at the cost of an increase in binary size">,
   NegFlag<SetFalse, [], "Disable ODR indicator globals">>,
   Group<f_clang_Group>;
 def sanitize_address_destructor_EQ
     : Joined<["-"], "fsanitize-address-destructor=">,
       Flags<[CC1Option]>,
       HelpText<"Set destructor type used in ASan instrumentation">,

clang/lib/Driver/SanitizerArgs.cpp

if (AllAddedKinds & SanitizerKind::Address) {
     // globals in ASan is disabled by default on most ELF targets.
     // See https://sourceware.org/bugzilla/show_bug.cgi?id=19002
     AsanGlobalsDeadStripping = Args.hasFlag(
         options::OPT_fsanitize_address_globals_dead_stripping,
         options::OPT_fno_sanitize_address_globals_dead_stripping,
         !TC.getTriple().isOSBinFormatELF() || TC.getTriple().isOSFuchsia() ||
             TC.getTriple().isPS());
 
+    // Enable ODR indicators which allow better handling of mixed instrumented
+    // and uninstrumented globals. Disable them for Windows where weak odr
+    // indicators (.weak.__odr_asan_gen*) may cause multiple definition linker
+    // errors in the absence of -lldmingw.
     AsanUseOdrIndicator =
         Args.hasFlag(options::OPT_fsanitize_address_use_odr_indicator,
                      options::OPT_fno_sanitize_address_use_odr_indicator,
-                     AsanUseOdrIndicator);
+                     !TC.getTriple().isOSWindows());
 
     if (AllAddedKinds & SanitizerKind::PointerCompare & ~AllRemove) {
       AsanInvalidPointerCmp = true;
     }
 
     if (AllAddedKinds & SanitizerKind::PointerSubtract & ~AllRemove) {
       AsanInvalidPointerSub = true;
     }
if (AsanUseAfterScope)
     CmdArgs.push_back("-fsanitize-address-use-after-scope");
 
   if (AsanPoisonCustomArrayCookie)
     CmdArgs.push_back("-fsanitize-address-poison-custom-array-cookie");
 
   if (AsanGlobalsDeadStripping)
     CmdArgs.push_back("-fsanitize-address-globals-dead-stripping");
 
-  if (AsanUseOdrIndicator)
-    CmdArgs.push_back("-fsanitize-address-use-odr-indicator");
+  if (!AsanUseOdrIndicator)
+    CmdArgs.push_back("-fno-sanitize-address-use-odr-indicator");
 
   if (AsanInvalidPointerCmp) {
     CmdArgs.push_back("-mllvm");
     CmdArgs.push_back("-asan-detect-invalid-pointer-cmp");
   }
 
   if (AsanInvalidPointerSub) {
     CmdArgs.push_back("-mllvm");

clang/test/CodeGen/asan-globals-odr.cpp

-// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefixes=CHECK,INDICATOR0,GLOB_VAR,ALIAS0
-// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefixes=CHECK,INDICATOR1,GLOB_ALIAS_INDICATOR,ALIAS1
+// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefixes=CHECK,INDICATOR1,GLOB_ALIAS_INDICATOR,ALIAS1
 // RUN: %clang_cc1 -fsanitize=address -fno-sanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefixes=CHECK,INDICATOR0,GLOB_VAR,ALIAS0
 // RUN: %clang_cc1 -fsanitize=address -fno-sanitize-address-use-odr-indicator -fsanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefixes=CHECK,INDICATOR1,GLOB_ALIAS_INDICATOR,ALIAS1
 // RUN: %clang_cc1 -fsanitize=address -fsanitize-address-use-odr-indicator -fno-sanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefixes=CHECK,INDICATOR0,GLOB_VAR,ALIAS0
 
 // No alias on Windows but indicators should work.
-// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefixes=CHECK,GLOB_VAR,ALIAS0
-// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefixes=CHECK,INDICATOR1,GLOB_VAR_INDICATOR,ALIAS0
+// RUN: %clang_cc1 -fsanitize=address -fno-sanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefixes=CHECK,GLOB_VAR,ALIAS0
+// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefixes=CHECK,INDICATOR1,GLOB_VAR_INDICATOR,ALIAS0
 
 int global;
 
 int main() {
   return global;
 }
 
 // CHECK: [[VAR:@.*global.*]] ={{.*}} global { i32, [28 x i8] } zeroinitializer, align 32

clang/test/CodeGen/asan-static-odr.cpp

-// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s
+// RUN: %clang_cc1 -fsanitize=address -fno-sanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s
 
 // No alias on Windows but indicators should work.
-// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s
+// RUN: %clang_cc1 -fsanitize=address -fno-sanitize-address-use-odr-indicator -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s
 
 static int global;
 
 int main() {
   return global;
 }
 
 // CHECK-NOT: __odr_asan_gen
 // CHECK-NOT: private alias
 // CHECK: [[VAR:@.*global.*]] ={{.*}} global { i32, [28 x i8] } zeroinitializer, align 32
 // CHECK: @0 = internal global {{.*}} [[VAR]] to i64), {{.*}}, i64 -1 }]
 // CHECK: call void @__asan_register_globals(i64 ptrtoint (ptr @0 to i64), i64 1)
 // CHECK: call void @__asan_unregister_globals(i64 ptrtoint (ptr @0 to i64), i64 1)

clang/test/Driver/fsanitize.c

 // RUN:     FileCheck %s --check-prefix=CHECK-ASAN-OUTLINE-OK
 // CHECK-ASAN-OUTLINE-OK: "-mllvm" "-asan-instrumentation-with-call-threshold=0"
 // RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fno-sanitize-address-outline-instrumentation %s -### 2>&1 | \
 // RUN:     FileCheck %s --check-prefix=CHECK-NO-CHECK-ASAN-CALLBACK
 // RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fsanitize-address-outline-instrumentation -fno-sanitize-address-outline-instrumentation %s -### 2>&1 | \
 // RUN:     FileCheck %s --check-prefix=CHECK-NO-CHECK-ASAN-CALLBACK
 // CHECK-NO-CHECK-ASAN-CALLBACK-NOT: "-mllvm" "-asan-instrumentation-with-call-threshold=0"
 
-// RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fsanitize-address-use-odr-indicator %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR
-// RUN: %clang_cl --target=x86_64-windows -fsanitize=address -fsanitize-address-use-odr-indicator -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR
-// CHECK-ASAN-ODR-INDICATOR: -cc1{{.*}}-fsanitize-address-use-odr-indicator
+// RUN: %clang --target=x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR
+// RUN: %clang_cl --target=x86_64-windows -fsanitize=address -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR-OFF
+// CHECK-ASAN-ODR-INDICATOR-NOT: "-fsanitize-address-use-odr-indicator"
 
 // RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fno-sanitize-address-use-odr-indicator %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR-OFF
 // RUN: %clang_cl --target=x86_64-windows -fsanitize=address -fno-sanitize-address-use-odr-indicator -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR-OFF
-// CHECK-ASAN-ODR-INDICATOR-OFF-NOT: -cc1{{.*}}address-generate-odr-globals
+// CHECK-ASAN-ODR-INDICATOR-OFF: "-cc1" {{.*}} "-fno-sanitize-address-use-odr-indicator"
 
-// RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fno-sanitize-address-use-odr-indicator -fsanitize-address-use-odr-indicator %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR-BOTH
-// RUN: %clang_cl --target=x86_64-windows -fsanitize=address -fno-sanitize-address-use-odr-indicator -fsanitize-address-use-odr-indicator -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR-BOTH
-// CHECK-ASAN-ODR-INDICATOR-BOTH: -cc1{{.*}}-fsanitize-address-use-odr-indicator
+// RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fno-sanitize-address-use-odr-indicator -fsanitize-address-use-odr-indicator %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR
+// RUN: %clang_cl --target=x86_64-windows -fsanitize=address -fno-sanitize-address-use-odr-indicator -fsanitize-address-use-odr-indicator -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR
 
-// RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fsanitize-address-use-odr-indicator -fno-sanitize-address-use-odr-indicator %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR-BOTH-OFF
-// CHECK-ASAN-ODR-INDICATOR-BOTH-OFF-NOT: -cc1{{.*}}address-generate-odr-globals
-
-// RUN: %clang --target=x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-WITHOUT-ODR-INDICATOR
-// CHECK-ASAN-WITHOUT-ODR-INDICATOR-NOT: -cc1{{.*}}address-generate-odr-globals
+// RUN: %clang --target=x86_64-linux-gnu -fsanitize=address -fsanitize-address-use-odr-indicator -fno-sanitize-address-use-odr-indicator %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-ODR-INDICATOR-OFF
 
 // RUN: %clang --target=x86_64-linux-gnu -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ONLY-TRACK-ORIGINS
 // CHECK-ONLY-TRACK-ORIGINS: warning: argument unused during compilation: '-fsanitize-memory-track-origins'
 
 // RUN: %clang --target=x86_64-linux-gnu -fsanitize=memory -fno-sanitize=memory -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-DISABLED-MSAN
 // CHECK-TRACK-ORIGINS-DISABLED-MSAN-NOT: warning: argument unused
 
 // RUN: %clang --target=x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-NO-EXTRA-TRACK-ORIGINS

compiler-rt/test/asan/TestCases/Linux/odr-violation.cpp

 // FIXME: https://code.google.com/p/address-sanitizer/issues/detail?id=316
 // XFAIL: android
 // Fails with debug checks: https://bugs.llvm.org/show_bug.cgi?id=46862
 // XFAIL: !compiler-rt-optimized && !riscv64
 //
 // We use fast_unwind_on_malloc=0 to have full unwinding even w/o frame
 // pointers. This setting is not on by default because it's too expensive.
 //
+// Note, -asan-use-private-alias=1 -asan-use-odr-indicator=1 is the default.
+// -fno-sanitize-address-use-odr-indicator turns off both.
+//
 // Different size: detect a bug if detect_odr_violation>=1
-// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared %s -o %dynamiclib
-// RUN: %clangxx_asan -g %s %ld_flags_rpath_exe -o %t-ODR-EXE
+// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared -fno-sanitize-address-use-odr-indicator %s -o %dynamiclib
+// RUN: %clangxx_asan -g -fno-sanitize-address-use-odr-indicator %s %ld_flags_rpath_exe -o %t-ODR-EXE
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=1 not %run %t-ODR-EXE 2>&1 | FileCheck %s
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=2 not %run %t-ODR-EXE 2>&1 | FileCheck %s
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=0     %run %t-ODR-EXE 2>&1 | FileCheck %s --check-prefix=DISABLED
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0                        not %run %t-ODR-EXE 2>&1 | FileCheck %s
 //
 // Same size: report a bug only if detect_odr_violation>=2.
-// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared %s -o %dynamiclib -DSZ=100
+// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared -fno-sanitize-address-use-odr-indicator %s -o %dynamiclib -DSZ=100
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=1     %run %t-ODR-EXE 2>&1 | FileCheck %s --check-prefix=DISABLED
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=2 not %run %t-ODR-EXE 2>&1 | FileCheck %s
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0                        not %run %t-ODR-EXE 2>&1 | FileCheck %s
 // RUN: echo "odr_violation:foo::ZZZ" > %t.supp
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=2:suppressions=%t.supp  not %run %t-ODR-EXE 2>&1 | FileCheck %s
 // RUN: echo "odr_violation:foo::G" > %t.supp
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=2:suppressions=%t.supp      %run %t-ODR-EXE 2>&1 | FileCheck %s --check-prefix=DISABLED
 // RUN: rm -f %t.supp
 //
 // Use private aliases for global variables without indicator symbol.
-// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared -mllvm -asan-use-private-alias %s -o %dynamiclib -DSZ=100
-// RUN: %clangxx_asan -g -mllvm -asan-use-private-alias %s %ld_flags_rpath_exe -o %t-ODR-EXE
+// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared -mllvm -asan-use-odr-indicator=0 %s -o %dynamiclib -DSZ=100
+// RUN: %clangxx_asan -g -mllvm -asan-use-odr-indicator=0 %s %ld_flags_rpath_exe -o %t-ODR-EXE
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0 %run %t-ODR-EXE 2>&1 | FileCheck %s --check-prefix=DISABLED
 
 // Use private aliases for global variables: use indicator symbol to detect ODR violation.
-// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared -mllvm -asan-use-private-alias -mllvm -asan-use-odr-indicator  %s -o %dynamiclib -DSZ=100
-// RUN: %clangxx_asan -g -mllvm -asan-use-private-alias -mllvm -asan-use-odr-indicator %s %ld_flags_rpath_exe -o %t-ODR-EXE
+// RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared %s -o %dynamiclib -DSZ=100
+// RUN: %clangxx_asan -g %s %ld_flags_rpath_exe -o %t-ODR-EXE
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0 not %run %t-ODR-EXE 2>&1 | FileCheck %s
 
 // Same as above but with clang switches.
 // RUN: %clangxx_asan -g -DBUILD_SO=1 -fPIC -shared -fsanitize-address-use-odr-indicator %s -o %dynamiclib -DSZ=100
 // RUN: %clangxx_asan -g -fsanitize-address-use-odr-indicator %s %ld_flags_rpath_exe -o %t-ODR-EXE
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0 not %run %t-ODR-EXE 2>&1 | FileCheck %s
 
 // GNU driver doesn't handle .so files properly.

compiler-rt/test/asan/TestCases/Linux/odr_indicators.cpp

-// RUN: %clangxx_asan -fPIC %s -o %t
+// RUN: %clangxx_asan -fno-sanitize-address-use-odr-indicator -fPIC %s -o %t
 // RUN: %env_asan_opts=report_globals=2 %run %t 2>&1 | FileCheck %s --check-prefixes=CHECK,INDICATOR0
 
 // RUN: %clangxx_asan -fsanitize-address-use-odr-indicator -fPIC %s -o %t
 // RUN: %env_asan_opts=report_globals=2 %run %t 2>&1 | FileCheck %s --check-prefixes=CHECK,INDICATOR1
 
 #include <stdio.h>
 
 int test_global_1;

llvm/include/llvm/Transforms/Instrumentation/AddressSanitizer.h

 /// Public interface to the address sanitizer module pass for instrumenting code
 /// to check for various memory errors.
 ///
 /// This adds 'asan.module_ctor' to 'llvm.global_ctors'. This pass may also
 /// run intependently of the function address sanitizer.
 class AddressSanitizerPass : public PassInfoMixin<AddressSanitizerPass> {
 public:
   AddressSanitizerPass(const AddressSanitizerOptions &Options,
-                       bool UseGlobalGC = true, bool UseOdrIndicator = false,
+                       bool UseGlobalGC = true, bool UseOdrIndicator = true,
                        AsanDtorKind DestructorKind = AsanDtorKind::Global);
   PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
   void printPipeline(raw_ostream &OS,
                      function_ref<StringRef(StringRef)> MapClassName2PassName);
   static bool isRequired() { return true; }
 
 private:
   AddressSanitizerOptions Options;

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

 static cl::opt<uint32_t> ClForceExperiment(
     "asan-force-experiment",
     cl::desc("Force optimization experiment (for testing)"), cl::Hidden,
     cl::init(0));
 
 static cl::opt<bool>
     ClUsePrivateAlias("asan-use-private-alias",
                       cl::desc("Use private aliases for global variables"),
-                      cl::Hidden, cl::init(false));
+                      cl::Hidden, cl::init(true));
 
 static cl::opt<bool>
     ClUseOdrIndicator("asan-use-odr-indicator",
                       cl::desc("Use odr indicators to improve ODR reporting"),
-                      cl::Hidden, cl::init(false));
+                      cl::Hidden, cl::init(true));
 
 static cl::opt<bool>
     ClUseGlobalsGC("asan-globals-live-support",
                    cl::desc("Use linker features to support dead "
                             "code stripping of globals"),
                    cl::Hidden, cl::init(true));
 
 // This is on by default even though there is a bug in gold:
private:
   FunctionCallee AMDGPUAddressShared;
   FunctionCallee AMDGPUAddressPrivate;
 };
 
 class ModuleAddressSanitizer {
 public:
   ModuleAddressSanitizer(Module &M, bool CompileKernel = false,
                          bool Recover = false, bool UseGlobalsGC = true,
-                         bool UseOdrIndicator = false,
+                         bool UseOdrIndicator = true,
                          AsanDtorKind DestructorKind = AsanDtorKind::Global)
       : CompileKernel(ClEnableKasan.getNumOccurrences() > 0 ? ClEnableKasan
                                                             : CompileKernel),
         Recover(ClRecover.getNumOccurrences() > 0 ? ClRecover : Recover),
         UseGlobalsGC(UseGlobalsGC && ClUseGlobalsGC && !this->CompileKernel),
         // Enable aliases as they should have no downside with ODR indicators.
-        UsePrivateAlias(UseOdrIndicator || ClUsePrivateAlias),
-        UseOdrIndicator(UseOdrIndicator || ClUseOdrIndicator),
+        UsePrivateAlias(ClUsePrivateAlias.getNumOccurrences() > 0
+                            ? ClUsePrivateAlias
+                            : UseOdrIndicator),
+        UseOdrIndicator(ClUseOdrIndicator.getNumOccurrences() > 0
+                            ? ClUseOdrIndicator
+                            : UseOdrIndicator),
         // Not a typo: ClWithComdat is almost completely pointless without
         // ClUseGlobalsGC (because then it only works on modules without
         // globals, which are rare); it is a prerequisite for ClUseGlobalsGC;
         // and both suffer from gold PR19002 for which UseGlobalsGC constructor
         // argument is designed as workaround. Therefore, disable both
         // ClWithComdat and ClUseGlobalsGC unless the frontend says it's ok to
         // do globals-gc.
         UseCtorComdat(UseGlobalsGC && ClWithComdat && !this->CompileKernel),

llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll

 @dyn_init_global = global i32 0, align 4
 @blocked_global = global i32 0, align 4
 @_ZZ4funcvE10static_var = internal global i32 0, align 4
 @.str = private unnamed_addr constant [14 x i8] c"Hello, world!\00", align 1
 @llvm.global_ctors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 65535, ptr @_GLOBAL__sub_I_asan_globals.cpp, ptr null }]
 
 ; Check that globals were instrumented:
 
-; CHECK: @global = global { i32, [28 x i8] } zeroinitializer, align 32
-; CHECK: @.str = internal constant { [14 x i8], [18 x i8] } { [14 x i8] c"Hello, world!\00", [18 x i8] zeroinitializer }, align 32
+; CHECK: @global = global { i32, [28 x i8] } zeroinitializer, comdat, align 32
+; CHECK: @.str = internal constant { [14 x i8], [18 x i8] } { [14 x i8] c"Hello, world!\00", [18 x i8] zeroinitializer }, comdat({{.*}}), align 32
 
 ; Check emitted location descriptions:
 ; CHECK: [[VARNAME:@___asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
 ; NOALIAS: @__asan_global_global = {{.*}}i64 ptrtoint (ptr @global to i64){{.*}} section "asan_globals"{{.*}}, !associated
 ; NOALIAS: @__asan_global_.str = {{.*}}i64 ptrtoint (ptr @{{.str|1}} to i64){{.*}} section "asan_globals"{{.*}}, !associated
 ; ALIAS: @__asan_global_global = {{.*}}i64 ptrtoint (ptr @0 to i64){{.*}} section "asan_globals"{{.*}}, !associated
 ; ALIAS: @__asan_global_.str = {{.*}}i64 ptrtoint (ptr @4 to i64){{.*}} section "asan_globals"{{.*}}, !associated
 

llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll

 ; Check that we disable the use of comdat sections for the garbage collection
 ; of globals.
 ; This is to avoid false negative ODR violations detection at link time.
 ; We keep using comdats for garbage collection if odr indicators are
 ; enabled as indicator symbols will cause link time odr violations.
 ; This is to fix PR 47925.
 ;
-; RUN: opt < %s -passes=asan             -asan-globals-live-support=1 -S | FileCheck %s --check-prefixes=CHECK,NOCOMDAT
+; RUN: opt < %s -passes=asan -asan-globals-live-support=1 -asan-use-odr-indicator=0 -S | FileCheck %s --check-prefixes=CHECK,NOCOMDAT
 ; Check that enabling odr indicators enables comdat for globals.
-; RUN: opt < %s -passes=asan             -asan-globals-live-support=1 -asan-use-odr-indicator=1 -S | FileCheck %s --check-prefixes=CHECK,COMDAT
+; RUN: opt < %s -passes=asan -asan-globals-live-support=1 -S | FileCheck %s --check-prefixes=CHECK,COMDAT
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 ; Globals:
 @global = global i32 0, align 4
 @dyn_init_global = global i32 0, align 4
 @blocked_global = global i32 0, align 4
 @_ZZ4funcvE10static_var = internal global i32 0, align 4

 
 ; NOCOMDAT: @global = global { i32, [28 x i8] } zeroinitializer, align 32
 ; NOCOMDAT: @dyn_init_global = global { i32, [28 x i8] } zeroinitializer, align 32
 ; NOCOMDAT: @_ZZ4funcvE10static_var = internal global { i32, [28 x i8] } zeroinitializer, align 32
 ; NOCOMDAT: @.str = internal constant { [14 x i8], [18 x i8] } { [14 x i8] c"Hello, world!\00", [18 x i8] zeroinitializer }, align 32
 
 ; Check emitted location descriptions:
 ; CHECK: [[VARNAME:@___asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
-; COMDAT: @__asan_global_global = {{.*}}i64 ptrtoint (ptr @global to i64){{.*}} section "asan_globals"{{.*}}, !associated
-; COMDAT: @__asan_global_.str = {{.*}}i64 ptrtoint (ptr @{{.str|1}} to i64){{.*}} section "asan_globals"{{.*}}, !associated
+; COMDAT: @__asan_global_global = {{.*}}i64 ptrtoint (ptr @__odr_asan_gen_global to i64){{.*}} section "asan_globals"{{.*}}, comdat($global), !associated
+; COMDAT: @__asan_global_.str = {{.*}}i64 ptrtoint (ptr @___asan_gen_ to i64){{.*}} section "asan_globals"{{.*}}, comdat($.str.{{.*}}), !associated
 
 ; The metadata has to be inserted to llvm.compiler.used to avoid being stripped
 ; during LTO.
 ; CHECK: @llvm.compiler.used {{.*}} ptr @__asan_global_global, {{.*}} section "llvm.metadata"
 
 ; Check that location descriptors and global names were passed into __asan_register_globals:
 ; CHECK: call void @__asan_register_elf_globals(i64 ptrtoint (ptr @___asan_globals_registered to i64), i64 ptrtoint (ptr @__start_asan_globals to i64), i64 ptrtoint (ptr @__stop_asan_globals to i64))
 

llvm/test/Instrumentation/AddressSanitizer/local_alias.ll

 ; Defaults
-; RUN: opt < %s -passes=asan -S | FileCheck %s --check-prefixes=CHECK-NOALIAS,CHECK-NOINDICATOR
+; RUN: opt < %s -passes=asan -S | FileCheck %s --check-prefixes=CHECK-ALIAS,CHECK-INDICATOR
 
 ; {newPM,legacyPM} x {alias0,alias1} x {odr0,odr1}
 ; RUN: opt < %s -passes=asan             -asan-use-private-alias=0 -asan-use-odr-indicator=0 -S | FileCheck %s --check-prefixes=CHECK-NOALIAS,CHECK-NOINDICATOR
 ; RUN: opt < %s -passes=asan             -asan-use-private-alias=1 -asan-use-odr-indicator=0 -S | FileCheck %s --check-prefixes=CHECK-ALIAS,CHECK-NOINDICATOR
 ; RUN: opt < %s -passes=asan             -asan-use-private-alias=0 -asan-use-odr-indicator=1 -S | FileCheck %s --check-prefixes=CHECK-NOALIAS,CHECK-INDICATOR
 ; RUN: opt < %s -passes=asan             -asan-use-private-alias=1 -asan-use-odr-indicator=1 -S | FileCheck %s --check-prefixes=CHECK-ALIAS,CHECK-INDICATOR
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"

llvm/test/Instrumentation/AddressSanitizer/odr-check-ignore.ll

-; RUN: opt < %s -passes=asan -asan-use-private-alias=0 -S | FileCheck %s --check-prefix=NOALIAS
-; RUN: opt < %s -passes=asan -asan-use-private-alias=1 -S | FileCheck %s --check-prefix=ALIAS
+; RUN: opt < %s -passes=asan -asan-use-odr-indicator=0 -asan-use-private-alias=0 -S | FileCheck %s --check-prefix=NOALIAS
+; RUN: opt < %s -passes=asan -asan-use-odr-indicator=0 -asan-use-private-alias=1 -S | FileCheck %s --check-prefix=ALIAS
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @a = global [2 x i32] zeroinitializer, align 4
 @b = private global [2 x i32] zeroinitializer, align 4
 @c = internal global [2 x i32] zeroinitializer, align 4
 @d = unnamed_addr global [2 x i32] zeroinitializer, align 4

llvm/test/Instrumentation/AddressSanitizer/win-string-literal.ll

-; RUN: opt < %s -passes=asan -S | FileCheck %s
+; RUN: opt < %s -passes=asan -asan-use-odr-indicator=0 -asan-use-private-alias=0 -S | FileCheck %s
 
 ; Generated like so:
 ; $ clang -S -emit-llvm -Xclang -disable-llvm-passes -fsanitize=address -O1 t.cpp -o t.ll
 ; const char *getstr() { return "asdf"; }
 
 ; CHECK: $"??_C@_04JIHMPGLA@asdf?$AA@" = comdat any
 
 ; CHECK: @"??_C@_04JIHMPGLA@asdf?$AA@" =