Fix exception_wrapper::throwException when called before main

Summary:
[Folly] Fix `exception_wrapper::throwException` when called before `main`.

When the `exception_wrapper` is empty, then `throwException` emits a message to `std::cerr` and terminates. If called before `main` begins or after `main` ends, then `std::cerr` might not have been constructed yet or might have already been destructed. Bad. Segfault, etc. So we need to ensure that `std::cerr` is alive by holding an instance of `std::ios_base::Init`.

Reviewed By: Orvid

Differential Revision: D4576190

fbshipit-source-id: dd84b5e82eb6bd817d405baf530714e0f4c314c5

diff --git a/folly/ExceptionWrapper.cpp b/folly/ExceptionWrapper.cpp
index d819c603e269ccfc812708931b2e605eb24177a8..c6ad16675955544b311ea55a57f8fafa413a3ac1 100644 (file)
--- a/folly/ExceptionWrapper.cpp
+++ b/folly/ExceptionWrapper.cpp
@@ -26,6 +26,7 @@ namespace folly {
   } else if (eptr_) {
     std::rethrow_exception(eptr_);
   }
+  std::ios_base::Init ioinit_; // ensure std::cerr is alive
   std::cerr
       << "Cannot use `throwException` with an empty folly::exception_wrapper"
       << std::endl;