[libc++] Honor __SANITIZER_DISABLE_CONTAINER_OVERFLOW__ in libc++

Address sanitizer recently got a new macro __SANITIZER_DISABLE_CONTAINER_OVERFLOW__
which is intended to disable container overflow checks in libraries
(either the standard library or user libraries that might provide such
checks). This patch makes libc++ honor that macro and, in addition,
cleans up how these checks are enabled for string (which is special)
by introducing a macro just for string.

Author: ldionne

libcxx/include/__debug_utils/sanitizers.h

@@ -17,7 +17,16 @@
 #  pragma GCC system_header
 #endif
 
-#if __has_feature(address_sanitizer)
+// _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS determines whether the containers should provide ASAN container
+// overflow checks. Some containers like std::string need stricter requirements in order to enable these
+// checks and also need to check that the library was built with sanitizer support (_LIBCPP_INSTRUMENTED_WITH_ASAN).
+#if __has_feature(address_sanitizer) && !defined(__SANITIZER_DISABLE_CONTAINER_OVERFLOW__)
+#  define _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS 1
+#else
+#  define _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS 0
+#endif
+
+#if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
 
 extern "C" {
 _LIBCPP_EXPORTED_FROM_ABI void
@@ -28,12 +37,12 @@ _LIBCPP_EXPORTED_FROM_ABI int
 __sanitizer_verify_double_ended_contiguous_container(const void*, const void*, const void*, const void*);
 }
 
-#endif // __has_feature(address_sanitizer)
+#endif // _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // ASan choices
-#if __has_feature(address_sanitizer)
+#if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
 #  define _LIBCPP_HAS_ASAN_CONTAINER_ANNOTATIONS_FOR_ALL_ALLOCATORS 1
 #endif
 
@@ -57,7 +66,7 @@ _LIBCPP_HIDE_FROM_ABI void __annotate_double_ended_contiguous_container(
     const void* __last_old_contained,
     const void* __first_new_contained,
     const void* __last_new_contained) {
-#if !__has_feature(address_sanitizer)
+#if !_LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
   (void)__first_storage;
   (void)__last_storage;
   (void)__first_old_contained;
@@ -86,7 +95,7 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void __annotate_contiguous_c
     const void* __last_storage,
     const void* __old_last_contained,
     const void* __new_last_contained) {
-#if !__has_feature(address_sanitizer)
+#if !_LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
   (void)__first_storage;
   (void)__last_storage;
   (void)__old_last_contained;

libcxx/include/deque

@@ -932,7 +932,7 @@ private:
     (void)__end;
     (void)__annotation_type;
     (void)__place;
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     // __beg - index of the first item to annotate
     // __end - index behind the last item to annotate (so last item + 1)
     // __annotation_type - __asan_unposion or __asan_poison
@@ -1025,23 +1025,23 @@ private:
       std::__annotate_double_ended_contiguous_container<_Allocator>(
           __mem_beg, __mem_end, __old_beg, __old_end, __new_beg, __new_end);
     }
-#  endif // __has_feature(address_sanitizer)
+#  endif // _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
   }
 
   _LIBCPP_HIDE_FROM_ABI void __annotate_new(size_type __current_size) const _NOEXCEPT {
     (void)__current_size;
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     if (__current_size == 0)
       __annotate_from_to(0, __map_.size() * __block_size, __asan_poison, __asan_back_moved);
     else {
       __annotate_from_to(0, __start_, __asan_poison, __asan_front_moved);
       __annotate_from_to(__start_ + __current_size, __map_.size() * __block_size, __asan_poison, __asan_back_moved);
     }
-#  endif // __has_feature(address_sanitizer)
+#  endif // _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
   }
 
   _LIBCPP_HIDE_FROM_ABI void __annotate_delete() const _NOEXCEPT {
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     if (empty()) {
       for (size_t __i = 0; __i < __map_.size(); ++__i) {
         __annotate_whole_block(__i, __asan_unposion);
@@ -1050,35 +1050,35 @@ private:
       __annotate_from_to(0, __start_, __asan_unposion, __asan_front_moved);
       __annotate_from_to(__start_ + size(), __map_.size() * __block_size, __asan_unposion, __asan_back_moved);
     }
-#  endif // __has_feature(address_sanitizer)
+#  endif // _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
   }
 
   _LIBCPP_HIDE_FROM_ABI void __annotate_increase_front(size_type __n) const _NOEXCEPT {
     (void)__n;
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     __annotate_from_to(__start_ - __n, __start_, __asan_unposion, __asan_front_moved);
 #  endif
   }
 
   _LIBCPP_HIDE_FROM_ABI void __annotate_increase_back(size_type __n) const _NOEXCEPT {
     (void)__n;
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     __annotate_from_to(__start_ + size(), __start_ + size() + __n, __asan_unposion, __asan_back_moved);
 #  endif
   }
 
   _LIBCPP_HIDE_FROM_ABI void __annotate_shrink_front(size_type __old_size, size_type __old_start) const _NOEXCEPT {
     (void)__old_size;
     (void)__old_start;
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     __annotate_from_to(__old_start, __old_start + (__old_size - size()), __asan_poison, __asan_front_moved);
 #  endif
   }
 
   _LIBCPP_HIDE_FROM_ABI void __annotate_shrink_back(size_type __old_size, size_type __old_start) const _NOEXCEPT {
     (void)__old_size;
     (void)__old_start;
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     __annotate_from_to(__old_start + size(), __old_start + __old_size, __asan_poison, __asan_back_moved);
 #  endif
   }
@@ -1091,7 +1091,7 @@ private:
   __annotate_whole_block(size_t __block_index, __asan_annotation_type __annotation_type) const _NOEXCEPT {
     (void)__block_index;
     (void)__annotation_type;
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
     __map_const_iterator __block_it = __map_.begin() + __block_index;
     const void* __block_start       = std::__to_address(*__block_it);
     const void* __block_end         = std::__to_address(*__block_it + __block_size);
@@ -1104,7 +1104,7 @@ private:
     }
 #  endif
   }
-#  if __has_feature(address_sanitizer)
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
 
 public:
   _LIBCPP_HIDE_FROM_ABI bool __verify_asan_annotations() const _NOEXCEPT {
@@ -1166,7 +1166,7 @@ public:
   }
 
 private:
-#  endif // __has_feature(address_sanitizer)
+#  endif // _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
   _LIBCPP_HIDE_FROM_ABI bool __maybe_remove_front_spare(bool __keep_one = true) {
     if (__front_spare_blocks() >= 2 || (!__keep_one && __front_spare_blocks())) {
       __annotate_whole_block(0, __asan_unposion);

libcxx/include/string

@@ -678,14 +678,18 @@ basic_string<char32_t> operator""s( const char32_t *str, size_t len );
 _LIBCPP_PUSH_MACROS
 #  include <__undef_macros>
 
-#  if __has_feature(address_sanitizer) && _LIBCPP_INSTRUMENTED_WITH_ASAN
+// Since std::string is partially instantiated in the built library, we require that the library
+// has been built with ASAN support in order to enable the container checks in std::string.
+//
+// The _LIBCPP_STRING_INTERNAL_MEMORY_ACCESS macro disables AddressSanitizer (ASan) instrumentation
+// for a specific function, allowing memory accesses that would normally trigger ASan errors to proceed
+// without crashing. This is useful for accessing parts of objects memory, which should not be accessed,
+// such as unused bytes in short strings, that should never be accessed by other parts of the program.
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS && _LIBCPP_INSTRUMENTED_WITH_ASAN
+#    define _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS_FOR_STRING 1
 #    define _LIBCPP_STRING_INTERNAL_MEMORY_ACCESS __attribute__((__no_sanitize__("address")))
-// This macro disables AddressSanitizer (ASan) instrumentation for a specific function,
-// allowing memory accesses that would normally trigger ASan errors to proceed without crashing.
-// This is useful for accessing parts of objects memory, which should not be accessed,
-// such as unused bytes in short strings, that should never be accessed
-// by other parts of the program.
 #  else
+#    define _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS_FOR_STRING 0
 #    define _LIBCPP_STRING_INTERNAL_MEMORY_ACCESS
 #  endif
 
@@ -749,7 +753,7 @@ public:
   //
   // This string implementation doesn't contain any references into itself. It only contains a bit that says whether
   // it is in small or large string mode, so the entire structure is trivially relocatable if its members are.
-#  if __has_feature(address_sanitizer) && _LIBCPP_INSTRUMENTED_WITH_ASAN
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS_FOR_STRING
   // When compiling with AddressSanitizer (ASan), basic_string cannot be trivially
   // relocatable. Because the object's memory might be poisoned when its content
   // is kept inside objects memory (short string optimization), instead of in allocated
@@ -764,7 +768,7 @@ public:
       void>;
 #  endif
 
-#  if __has_feature(address_sanitizer) && _LIBCPP_INSTRUMENTED_WITH_ASAN
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS_FOR_STRING
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pointer __asan_volatile_wrapper(pointer const& __ptr) const {
     if (__libcpp_is_constant_evaluated())
       return __ptr;
@@ -2321,7 +2325,7 @@ private:
   __annotate_contiguous_container(const void* __old_mid, const void* __new_mid) const {
     (void)__old_mid;
     (void)__new_mid;
-#  if _LIBCPP_INSTRUMENTED_WITH_ASAN
+#  if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS_FOR_STRING
 #    if defined(__APPLE__)
     // TODO: remove after addressing issue #96099 (https://llvm.org/PR96099)
     if (!__is_long())

libcxx/test/extensions/libcxx/asan/disable_container_overflow_checks.sh.cpp

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// XFAIL: FROZEN-CXX03-HEADERS-FIXME
+
+//
+// Check that libc++ honors when __SANITIZER_DISABLE_CONTAINER_OVERFLOW__ is set.
+//
+
+// RUN: %{cxx} %s %{flags} %{compile_flags} -D__SANITIZER_DISABLE_CONTAINER_OVERFLOW__
+// RUN: %{cxx} %s %{flags} %{compile_flags} -fsanitize=address -D__SANITIZER_DISABLE_CONTAINER_OVERFLOW__
+
+#include <vector>
+#include <string>
+#include <deque>
+
+#if _LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS
+#  error "Container overflow checks should be disabled in libc++"
+#endif
+
+int main(int, char**) {}

libcxx/test/libcxx/type_traits/is_trivially_relocatable.compile.pass.cpp

@@ -103,7 +103,7 @@ static_assert(!std::__libcpp_is_trivially_relocatable<std::array<NotTriviallyCop
 static_assert(std::__libcpp_is_trivially_relocatable<std::array<std::unique_ptr<int>, 1> >::value, "");
 
 // basic_string
-#if !__has_feature(address_sanitizer) || !_LIBCPP_INSTRUMENTED_WITH_ASAN
+#if !_LIBCPP_ENABLE_ASAN_CONTAINER_CHECKS_FOR_STRING
 struct MyChar {
   char c;
 };