Add the ability to defer the initialization of the SyzyAsan crash reporter.

syzygy/agent/asan/rtl_impl.h

Index: syzygy/agent/asan/rtl_impl.h
diff --git a/syzygy/agent/asan/rtl_impl.h b/syzygy/agent/asan/rtl_impl.h
index c9290bcb9c62f76417e62a61e7ec958287f9e00e..6db32b3245884b45387d45e1019f8796634d1906 100644
--- a/syzygy/agent/asan/rtl_impl.h
+++ b/syzygy/agent/asan/rtl_impl.h
@@ -105,7 +105,7 @@ void WINAPI asan_SetOnExceptionCallback(OnExceptionCallback callback);
 //    experiement.
 typedef void(WINAPI* AsanExperimentCallback)(const char* experiment_name,
                                              const char* experiment_group);
-// Calls @p callback once for each experiement this runtime is performing.
+// Calls @p callback once for each experiment this runtime is performing.
 // @param callback a function that will be invoked recursively zero or more
 //     times to enumerate the experiments and their state.
 void WINAPI asan_EnumExperiments(AsanExperimentCallback callback);
@@ -113,6 +113,29 @@ void WINAPI asan_EnumExperiments(AsanExperimentCallback callback);
 
 int asan_CrashForException(EXCEPTION_POINTERS* exception);
 
+// This functions allows manually initializing the crash reporter used by the
+// runtime.
+//
+// It should only be used if the deferred initialization flag has been used by
+// the instrumented image (via the corresponding environment variable or at
+// instrumentation time) and should only be called once. Trying to initialize
+// the crash reporter a second time will result in undefined behavior.
+//
+// Manually controlling the initialization of the crash reporter is useful when
+// there's no crash reporter available at initialization time (i.e. the
+// instrumented process hasn't been initialized it yet). In addition to
+// instrumenting with the deferred initialization flag, the instrumented image
+// should do something like the following:
+//
+//   InitializeCrashReporter();
+//   typedef VOID(WINAPI* SyzyAsanInitializeCrashReporterFn)();
+//   HMODULE handle = ::GetModuleHandle(L"syzyasan_rtl.dll");
+//   SyzyAsanInitializeCrashReporterFn syzyasan_init_crash_reporter =
+//       reinterpret_cast<SyzyAsanInitializeCrashReporterFn>(
+//             ::GetProcAddress(handle, "asan_InitializeCrashReporter"));
+//   syzyasan_init_crash_reporter();
+void WINAPI asan_InitializeCrashReporter();
+
 }  // extern "C"
 
 #endif  // SYZYGY_AGENT_ASAN_RTL_IMPL_H_