Handle LLVM_USE_SANITIZER=Address;Undefined (and the other way around)

[filcab]

Summary

Handle LLVM_USE_SANITIZER=Address;Undefined to enable ASan and UBSan
If UBSan is compatible with more of the other sanitizers, maybe we should
deal with this in a better way where we allow combining UBSan with any of
the other sanitizers.

[filcab]

Ping!

[samsonov]

LGTM after fixing a nit below. We don't plan to support running UBSan with any other sanitizer except for ASan in the short term.

cmake/modules/HandleLLVMOptions.cmake

401 ↗

(On Diff #18324)

You can use a single append() statement:

append("-fsanitize=address,undefined -fno-sanitize=...")

llvm/trunk/cmake/modules/HandleLLVMOptions.cmake

elseif (LLVM_USE_SANITIZER MATCHES "Memory(WithOrigins)?")
       endif()
     elseif (LLVM_USE_SANITIZER STREQUAL "Undefined")
       append_common_sanitizer_flags()
       append("-fsanitize=undefined -fno-sanitize=vptr,function -fno-sanitize-recover"
               CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     elseif (LLVM_USE_SANITIZER STREQUAL "Thread")
       append_common_sanitizer_flags()
       append("-fsanitize=thread" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+    elseif (LLVM_USE_SANITIZER STREQUAL "Address;Undefined" OR
+            LLVM_USE_SANITIZER STREQUAL "Undefined;Address")
+      append_common_sanitizer_flags()
+      append("-fsanitize=address,undefined -fno-sanitize=vptr,function -fno-sanitize-recover"
+              CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     else()
       message(WARNING "Unsupported value of LLVM_USE_SANITIZER: ${LLVM_USE_SANITIZER}")
     endif()
   else()
     message(WARNING "LLVM_USE_SANITIZER is not supported on this platform.")
   endif()
   if (LLVM_USE_SANITIZE_COVERAGE)
     append("-fsanitize-coverage=4" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)