[libcxx-commits] [libcxx] [libcxxabi] [ASan][libc++] std::basic_string annotations (PR #72677)

[Louis Dionne via libcxx-commits]

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@@ -543,6 +543,18 @@ function(cxx_add_basic_build_flags target)
   # library.
   target_compile_definitions(${target} PRIVATE -D_LIBCPP_BUILDING_LIBRARY)
 
+  # Define _LIBCPP_INSTRUMENTED_WITH_ASAN while building the library with ASan.
+  # Normally, the _LIBCPP_INSTRUMENTED_WITH_ASAN flag is used to keep information whether
+  # dylibs are built with AddressSanitizer. However, when building libc++,
+  # this flag needs to be defined so that the resulting dylib has all ASan functionalities normally guarded by this flag.
+  # If the _LIBCPP_INSTRUMENTED_WITH_ASAN flag is not defined, then parts of the ASan instrumentation code in libc++
+  # will not be compiled into it resulting in true positives.
+  # For context, read: https://github.com/llvm/llvm-project/pull/72677#pullrequestreview-1765402800
+  string(FIND "${LLVM_USE_SANITIZER}" "Address" building_with_asan)
+  if (NOT "${building_with_asan}" STREQUAL "-1")
+    target_compile_definitions(${target} PRIVATE -D_LIBCPP_INSTRUMENTED_WITH_ASAN)
+  endif()
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ldionne wrote:

You don't need this part since you are encoding it in the `__config_site` header. You can remove this but move the comment to below.

https://github.com/llvm/llvm-project/pull/72677