folly/Singleton: remove use of `link_whole`

Summary:
We used `link_whole` to make sure the `setStackTraceGetter` constructor is
always linked when using Singleton's to setup symbolizer for stack traces.
However, using `link_whole` means we always link in the singleton library, even
if it's never used.

This diff merges `SingletonStackTrace.cpp` into `Singleton.cpp` to avoid the
need for `link_whole` and to link the former if and only if we use the latter.

Reviewed By: pixelb

Differential Revision: D7230733

fbshipit-source-id: de9be51a4eefee201563523d25800ab19ea777e3

folly/Singleton.cpp

@@ -15,6 +15,7 @@
  */
 
 #include <folly/Singleton.h>
+#include <folly/portability/Config.h>
 
 #ifndef _WIN32
 #include <dlfcn.h>
@@ -30,6 +31,10 @@
 #include <folly/Format.h>
 #include <folly/ScopeGuard.h>
 
+#ifdef FOLLY_USE_SYMBOLIZER
+#include <folly/experimental/symbolizer/Symbolizer.h> // @manual
+#endif
+
 #if !defined(_WIN32) && !defined(__APPLE__) && !defined(__ANDROID__)
 #define FOLLY_SINGLETON_HAVE_DLSYM 1
 #endif
@@ -377,4 +382,46 @@ void SingletonVault::scheduleDestroyInstances() {
   std::atexit([] { SingletonVault::singleton()->destroyInstances(); });
 }
 
+// If we're using folly's Symbolizer, create a static initializer to setup
+// Singltone's to use it to print stack traces. It's important that we keep
+// this in the same compilation unit as the `SingletonVault` so that it's
+// setup/used iff singleton's are used.
+#ifdef FOLLY_USE_SYMBOLIZER
+namespace {
+
+std::string stackTraceGetter() {
+  // Get and symbolize stack trace
+  constexpr size_t kMaxStackTraceDepth = 100;
+  symbolizer::FrameArray<kMaxStackTraceDepth> addresses;
+
+  if (!getStackTraceSafe(addresses)) {
+    return "";
+  } else {
+    constexpr size_t kDefaultCapacity = 500;
+    symbolizer::ElfCache elfCache(kDefaultCapacity);
+
+    symbolizer::Symbolizer symbolizer(&elfCache);
+    symbolizer.symbolize(addresses);
+
+    symbolizer::StringSymbolizePrinter printer;
+    printer.println(addresses);
+    return printer.str();
+  }
+}
+
+struct SetStackTraceGetter {
+  SetStackTraceGetter() {
+    SingletonVault::stackTraceGetter().store(stackTraceGetter);
+  }
+};
+
+#ifdef __APPLE__
+// OS X doesn't support constructor priorities.
+SetStackTraceGetter setStackTraceGetter;
+#else
+SetStackTraceGetter __attribute__((__init_priority__(101))) setStackTraceGetter;
+#endif
+} // namespace
+#endif
+
 } // namespace folly

folly/SingletonStackTrace.cpp

-/*
- * Copyright 2015-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <folly/portability/Config.h>
-
-#ifdef FOLLY_USE_SYMBOLIZER
-#include <folly/Singleton.h>
-#include <folly/experimental/symbolizer/Symbolizer.h> // @manual
-
-namespace folly {
-
-namespace {
-
-std::string stackTraceGetter() {
-  // Get and symbolize stack trace
-  constexpr size_t kMaxStackTraceDepth = 100;
-  symbolizer::FrameArray<kMaxStackTraceDepth> addresses;
-
-  if (!getStackTraceSafe(addresses)) {
-    return "";
-  } else {
-    constexpr size_t kDefaultCapacity = 500;
-    symbolizer::ElfCache elfCache(kDefaultCapacity);
-
-    symbolizer::Symbolizer symbolizer(&elfCache);
-    symbolizer.symbolize(addresses);
-
-    symbolizer::StringSymbolizePrinter printer;
-    printer.println(addresses);
-    return printer.str();
-  }
-}
-
-struct SetStackTraceGetter {
-  SetStackTraceGetter() {
-    SingletonVault::stackTraceGetter().store(stackTraceGetter);
-  }
-};
-
-#ifdef __APPLE__
-// OS X doesn't support constructor priorities.
-SetStackTraceGetter setStackTraceGetter;
-#else
-SetStackTraceGetter __attribute__((__init_priority__(101))) setStackTraceGetter;
-#endif
-} // namespace
-} // namespace folly
-#endif