Index: lib/asan/asan_flags.inc
===================================================================
--- lib/asan/asan_flags.inc
+++ lib/asan/asan_flags.inc
@@ -161,3 +161,6 @@
 ASAN_FLAG(bool, verify_asan_link_order, true,
           "Check position of ASan runtime in library list (needs to be disabled"
           " when other library has to be preloaded system-wide)")
+ASAN_FLAG(bool, disable_init, false,
+          "If true, disables all initialization of the "
+          "sanitizer after flags are parsed. Only supported on Darwin.")
Index: lib/asan/asan_internal.h
===================================================================
--- lib/asan/asan_internal.h
+++ lib/asan/asan_internal.h
@@ -111,8 +111,14 @@
 
 void ReserveShadowMemoryRange(uptr beg, uptr end, const char *name);
 
-// Add convenient macro for interface functions that may be represented as
-// weak hooks.
+#if SANITIZER_SUPPORTS_DISABLED_INIT
+void HandleDisabledInit();
+#else
+void HandleDisabledInit() { Die(); }
+#endif
+
+// Add convenient macro for interface functions that may be represented
+// as weak hooks.
 #define ASAN_MALLOC_HOOK(ptr, size)                                   \
   do {                                                                \
     if (&__sanitizer_malloc_hook) __sanitizer_malloc_hook(ptr, size); \
Index: lib/asan/asan_malloc_mac.cc
===================================================================
--- lib/asan/asan_malloc_mac.cc
+++ lib/asan/asan_malloc_mac.cc
@@ -61,4 +61,13 @@
 
 #include "sanitizer_common/sanitizer_malloc_mac.inc"
 
+namespace COMMON_MALLOC_NAMESPACE {
+void HandleDisabledInit() {
+  // On the no init path make sure we still initialize the malloc zone
+  // so Symbolication clients (e.g. `leaks`) can find an initialized
+  // malloc zone when the sanitizer dylib gets dlopen()'ed.
+  InitMallocZoneFields();
+}
+}  // namespace COMMON_MALLOC_NAMESPACE
+
 #endif
Index: lib/asan/asan_rtl.cc
===================================================================
--- lib/asan/asan_rtl.cc
+++ lib/asan/asan_rtl.cc
@@ -396,6 +396,15 @@
   // initialization steps look at flags().
   InitializeFlags();
 
+  // Stop performing init if supported by the platform and it
+  // has been requested.
+  if (SANITIZER_SUPPORTS_DISABLED_INIT && UNLIKELY(flags()->disable_init)) {
+    asan_init_is_running = false;
+    Report("AddressSanitizer init has been disabled in this process.\n");
+    HandleDisabledInit();
+    return;
+  }
+
   AsanCheckIncompatibleRT();
   AsanCheckDynamicRTPrereqs();
   AvoidCVE_2016_2143();
Index: lib/sanitizer_common/sanitizer_platform.h
===================================================================
--- lib/sanitizer_common/sanitizer_platform.h
+++ lib/sanitizer_common/sanitizer_platform.h
@@ -342,4 +342,11 @@
 #define SANITIZER_SYMBOLIZER_MARKUP 0
 #endif
 
+// Enable ability to disable dynamic library initialization.
+#if SANITIZER_MAC
+#define SANITIZER_SUPPORTS_DISABLED_INIT 1
+#else
+#define SANITIZER_SUPPORTS_DISABLED_INIT 0
+#endif
+
 #endif // SANITIZER_PLATFORM_H
Index: test/asan/TestCases/Darwin/disable_init.cc
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/disable_init.cc
@@ -0,0 +1,26 @@
+// RUN: %clangxx -g -O0 %s -o %t
+// RUN: not --crash env ASAN_OPTIONS=disable_init=0 %run %t %shared_libasan
+// RUN: env ASAN_OPTIONS=disable_init=1 %run %t %shared_libasan
+#include <dlfcn.h>
+#include <stdio.h>
+
+int main(int argc, char **argv) {
+  if (argc != 2) {
+    fprintf(stderr, "Usage: %s <dylib_path>\n", argv[0]);
+    return 1;
+  }
+  const char *dylib_path = argv[1];
+  void *handle = dlopen(dylib_path, RTLD_LAZY);
+  if (!handle) {
+    fprintf(stderr, "Failed to dlopen: %s\n", dlerror());
+    return 1;
+  }
+  // Make sure we can find a function we expect to be in the dylib.
+  void *fn = dlsym(handle, "__sanitizer_mz_size");
+  if (!fn) {
+    fprintf(stderr, "Failed to get symbol: %s\n", dlerror());
+    return 1;
+  }
+  // TODO(dliew): Actually call a function from the dylib that is safe to call.
+  return 0;
+}