wrap and export __lsan_ignore_object

Summary: As we do for some of the other sanitizer interface points.

Reviewed By: luciang, dmm-fb

Differential Revision: D40360035

fbshipit-source-id: 8f0f58495e93f9a5a061eb29db89ac176a8664f9

folly/memory/SanitizeLeak.cpp

@@ -14,13 +14,34 @@
  * limitations under the License.
  */
 
+#include <folly/memory/SanitizeLeak.h>
+
 #include <mutex>
 #include <unordered_set>
 
-#include <folly/memory/SanitizeLeak.h>
+#include <folly/lang/Extern.h>
+
+//  Leak Sanitizer interface may be found at:
+//    https://github.com/llvm/llvm-project/blob/main/compiler-rt/include/sanitizer/lsan_interface.h
+extern "C" void __lsan_ignore_object(void const*);
+
+namespace {
+
+FOLLY_CREATE_EXTERN_ACCESSOR( //
+    lsan_ignore_object_access_v,
+    __lsan_ignore_object);
+
+constexpr bool E = folly::kIsLibrarySanitizeAddress;
+
+} // namespace
 
 namespace folly {
+
 namespace detail {
+
+FOLLY_STORAGE_CONSTEXPR lsan_ignore_object_t* const //
+    lsan_ignore_object_v = lsan_ignore_object_access_v<E>;
+
 namespace {
 struct LeakedPtrs {
   std::mutex mutex;

folly/memory/SanitizeLeak.h

@@ -21,10 +21,25 @@
 namespace folly {
 
 namespace detail {
+
+using lsan_ignore_object_t = void(void const*);
+
+extern lsan_ignore_object_t* const lsan_ignore_object_v;
+
 void annotate_object_leaked_impl(void const* ptr);
 void annotate_object_collected_impl(void const* ptr);
+
 } // namespace detail
 
+//  lsan_ignore_object
+//
+//  Marks an allocation to be treated as a root when Leak Sanitizer scans for
+//  leaked allocations.
+FOLLY_ALWAYS_INLINE static void lsan_ignore_object(void const* const ptr) {
+  auto fun = detail::lsan_ignore_object_v;
+  return kIsSanitizeAddress && fun ? fun(ptr) : void();
+}
+
 /**
  * When the current compilation unit is being compiled with ASAN enabled this
  * function will suppress an intentionally leaked pointer from the LSAN report.

folly/memory/test/SanitizeLeakTest.cpp

@@ -23,6 +23,13 @@
 
 namespace folly {
 
+TEST(SanitizeLeak, lsan_ignore_object) {
+  int* ptr = new int(5);
+  EXPECT_EQ(*ptr, 5);
+  lsan_ignore_object(ptr);
+  EXPECT_EQ(*ptr, 5);
+}
+
 TEST(SanitizeLeak, ImplementationAlwaysWorks) {
   int* ptr = new int(5);
   EXPECT_EQ(*ptr, 5);