Don't allow singleton use w/o registrationComplete()

Summary: This is same as D4249032, but for now this is only enabled in dbg and dev builds. I'm planning to bump this to FATAL later, once we fix know problematic main()s.

Reviewed By: lbrandy, yfeldblum

Differential Revision: D4821763

fbshipit-source-id: 5f7930f8cbcb10275d23a89848f1ec8ee34a8020

folly/Singleton-inl.h

@@ -230,6 +230,17 @@ void SingletonHolder<T>::createInstance() {
   creating_thread_.store(std::this_thread::get_id(), std::memory_order_release);
 
   auto state = vault_.state_.rlock();
+  if (vault_.type_ != SingletonVault::Type::Relaxed &&
+      !state->registrationComplete) {
+    auto stack_trace_getter = SingletonVault::stackTraceGetter().load();
+    auto stack_trace = stack_trace_getter ? stack_trace_getter() : "";
+    if (!stack_trace.empty()) {
+      stack_trace = "Stack trace:\n" + stack_trace;
+    }
+
+    LOG(DFATAL) << "Singleton " << type().name() << " requested before "
+                << "registrationComplete() call. " << stack_trace;
+  }
   if (state->state == SingletonVault::SingletonVaultState::Quiescing) {
     return;
   }

folly/Singleton.cpp

@@ -16,6 +16,10 @@
 
 #include <folly/Singleton.h>
 
+#ifndef _WIN32
+#include <dlfcn.h>
+#endif
+
 #include <atomic>
 #include <cstdio>
 #include <cstdlib>
@@ -24,8 +28,26 @@
 
 #include <folly/ScopeGuard.h>
 
+#if !defined(_WIN32) && !defined(__APPLE__)
+static void hs_init_weak(int* argc, char** argv[])
+    __attribute__((__weakref__("hs_init")));
+#endif
+
 namespace folly {
 
+SingletonVault::Type SingletonVault::defaultVaultType() {
+#if !defined(_WIN32) && !defined(__APPLE__)
+  bool isPython = dlsym(RTLD_DEFAULT, "Py_Main");
+  bool isHaskel = &::hs_init_weak || dlsym(RTLD_DEFAULT, "hs_init");
+  bool isJVM = dlsym(RTLD_DEFAULT, "JNI_GetCreatedJavaVMs");
+  bool isD = dlsym(RTLD_DEFAULT, "_d_run_main");
+
+  return isPython || isHaskel || isJVM || isD ? Type::Relaxed : Type::Strict;
+#else
+  return Type::Relaxed;
+#endif
+}
+
 namespace detail {
 
 [[noreturn]] void singletonWarnDoubleRegistrationAndAbort(

folly/Singleton.h

@@ -358,7 +358,9 @@ class SingletonVault {
     }
   };
 
-  explicit SingletonVault(Type type = Type::Strict) : type_(type) {}
+  static Type defaultVaultType();
+
+  explicit SingletonVault(Type type = defaultVaultType()) : type_(type) {}
 
   // Destructor is only called by unit tests to check destroyInstances.
   ~SingletonVault();