[CMake] Enable building with UBSAN + clang-cl on windows

[dwang]

Summary

Currently both ASAN and UBSAN are supported on Windows but only ASAN is enabled in LLVM build system. This patch enables the option to build LLVM with UBSAN on windows.

Tested with clang-cl released in LLVM16.

[dwang]

• Update ubsan_ignorelist to exempt false-positives for 0-sized objects. Build crashes if those files are not exempted.
• Refine HandleLLVMOptions.cmake

[andrewng]

Apart from the two nits, the CMake changes LGTM, although I haven't tested the patch myself. I'm not particularly familiar with UBSAN, so can't really comment on the other changes to ubsan_ignorelist.txt.

llvm/cmake/modules/HandleLLVMOptions.cmake

966

Perhaps supported by clang-cl?

llvm/utils/sanitizers/ubsan_ignorelist.txt

24

Should add newline to the end of the file for "UNIX" consumers.

[dwang]

fix error message & newline at end of file

[dwang]

rebase

[dwang]

For the ubsan ignore list, the newly added files reported ubsan crashes similiar to the one reported in: https://github.com/llvm/llvm-project/issues/61775

[pgousseau]

llvm/cmake/modules/HandleLLVMOptions.cmake

968

Could we add a succint comment to explain -D_ITERATOR_DEBUG_LEVEL=0 ? Is it for performance or to workaround a bug?

[dwang]

llvm/cmake/modules/HandleLLVMOptions.cmake

968

This was a workaround for debug level mismatch between UBSAN runtime and another module. Somehow the bug does not reproduce on latest master branch anymore. I will remove this.

[dwang]

Workaround UBSAN false-positive on 0-sized objects with __declspec(empty_bases)

[dwang]

For the UBSAN crashes, I found an alternative workaround here: https://github.com/llvm/llvm-project/issues/31914. Since the errors only reproduce on windows, this seems like a cleaner fix.
I have pushed an update to outline the necessary changes.

[pgousseau]

LGTM!

[dwang]

@pgousseau Thanks for the review!
Can you maybe commit this patch for me? I do not have push permission.

[dwang]

• format code

[dwang]

rebase against main

llvm/cmake/modules/HandleLLVMOptions.cmake

if (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
   add_flag_if_supported("-Wctad-maybe-unsupported" CTAD_MAYBE_UNSPPORTED_FLAG)
 endif (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
 
 if (LLVM_COMPILER_IS_GCC_COMPATIBLE AND NOT LLVM_ENABLE_WARNINGS)
   append("-w" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 endif()
 
 macro(append_common_sanitizer_flags)
-  if (NOT MSVC)
+  if (NOT MSVC OR CLANG_CL)
     # Append -fno-omit-frame-pointer and turn on debug info to get better
     # stack traces.
     add_flag_if_supported("-fno-omit-frame-pointer" FNO_OMIT_FRAME_POINTER)
     if (NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" AND
         NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "RELWITHDEBINFO")
       add_flag_if_supported("-gline-tables-only" GLINE_TABLES_ONLY)
     endif()
     # Use -O1 even in debug mode, otherwise sanitizers slowdown is too large.
elseif (LLVM_USE_SANITIZER STREQUAL "Address;Undefined" OR
             LLVM_USE_SANITIZER STREQUAL "Undefined;Address")
       append_common_sanitizer_flags()
       append("-fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
       append("${LLVM_UBSAN_FLAGS}" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     else()
       message(FATAL_ERROR "This sanitizer not yet supported in a MinGW environment: ${LLVM_USE_SANITIZER}")
     endif()
   elseif(MSVC)
-    if (LLVM_USE_SANITIZER STREQUAL "Address")
-      append_common_sanitizer_flags()
-      append("/fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
-      if (NOT CLANG_CL)
-        # Not compatible with /RTC flags.
-        foreach (flags_opt_to_scrub
-            CMAKE_CXX_FLAGS_${uppercase_CMAKE_BUILD_TYPE} CMAKE_C_FLAGS_${uppercase_CMAKE_BUILD_TYPE})
-          string (REGEX REPLACE "(^| )/RTC[1csu]*($| )" " "
-            "${flags_opt_to_scrub}" "${${flags_opt_to_scrub}}")
-        endforeach()
-      endif()
-      if (LINKER_IS_LLD_LINK)
-        if (LLVM_HOST_TRIPLE MATCHES "i[2-6]86-.*")
-          set(arch "i386")
-        else()
-          set(arch "x86_64")
-        endif()
+    if (NOT LLVM_USE_SANITIZER MATCHES "^(Address|Undefined|Address;Undefined|Undefined;Address)$")
+      message(FATAL_ERROR "This sanitizer not yet supported in the MSVC environment: ${LLVM_USE_SANITIZER}")
+    append_common_sanitizer_flags()
+      # Prepare ASAN runtime if needed
+      if (LLVM_USE_SANITIZER MATCHES ".*Address.*")
         if (${LLVM_USE_CRT_${uppercase_CMAKE_BUILD_TYPE}} MATCHES "^(MT|MTd)$")
           append("/wholearchive:clang_rt.asan-${arch}.lib /wholearchive:clang_rt.asan_cxx-${arch}.lib"
             CMAKE_EXE_LINKER_FLAGS)
           append("/wholearchive:clang_rt.asan_dll_thunk-${arch}.lib"
             CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
         else()
           append("clang_rt.asan_dynamic-${arch}.lib /wholearchive:clang_rt.asan_dynamic_runtime_thunk-${arch}.lib"
             CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
         endif()
       endif()
+    endif()
+    if (LLVM_USE_SANITIZER MATCHES ".*Address.*")
+      if (NOT CLANG_CL)
+        append("/fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+        # Not compatible with /RTC flags.
+        foreach (flags_opt_to_scrub
+            CMAKE_CXX_FLAGS_${uppercase_CMAKE_BUILD_TYPE} CMAKE_C_FLAGS_${uppercase_CMAKE_BUILD_TYPE})
+          string (REGEX REPLACE "(^| )/RTC[1csu]*($| )" " "
+            "${flags_opt_to_scrub}" "${${flags_opt_to_scrub}}")
+        endforeach()
       else()
-      message(FATAL_ERROR "This sanitizer not yet supported in the MSVC environment: ${LLVM_USE_SANITIZER}")
+        append("-fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)   
+      endif()     
+    endif()
+    if (LLVM_USE_SANITIZER MATCHES ".*Undefined.*") 
+      if (NOT CLANG_CL)
+        message(FATAL_ERROR "This sanitizer is only supported by clang-cl: Undefined")
+      endif()
+      append("-D_ITERATOR_DEBUG_LEVEL=0" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      append(${LLVM_UBSAN_FLAGS} CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     endif()
   else()
     message(FATAL_ERROR "LLVM_USE_SANITIZER is not supported on this platform.")
   endif()
   if (LLVM_USE_SANITIZE_COVERAGE)
     append("-fsanitize=fuzzer-no-link" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   endif()
   if (LLVM_USE_SANITIZER MATCHES ".*Undefined.*")

llvm/utils/sanitizers/ubsan_ignorelist.txt

 # This blacklist should be applied when LLVM is built
 # with -fsanitize=undefined instrumentation. It exists
 # because libstdc++ has some undefined behavior issues
 # in some of the headers, in particular, stl_tree.h.
 
 # upcast of address with insufficient space for an object of type std::_Rb_tree_node<...>
 src:*bits/stl_tree.h
 
 # libstdc++ 4.8 creates a null reference when calling
 # data() on an empty vector: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59829
 src:*bits/stl_iterator.h
 src:*bits/stl_vector.h
 
 # libstdc++ 8.0.1 casts an under-aligned pointer to type type_info:
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85930
 src:*bits/shared_ptr_base.h
+
+# UBSAN reports false-positive for 0-sized objects
+# https://github.com/llvm/llvm-project/issues/61775
+src:*/ADT/StringMap.h
+src:*/Support/AllocatorBase.h
+src:*/ADT/StringMapEntry.h
+src:*/ADT/SmallPtrSet.h