From: Yedidya Feldblum <yfeldblum@fb.com>
Date: Fri, 17 Feb 2017 05:07:49 +0000 (-0800)
Subject: Fix exception_wrapper::throwException when called before main
X-Git-Tag: v2017.03.06.00~28
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=05499631dc3e1160d673a7dd57e70fc797e532dc;p=folly.git

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 d819c603..c6ad1667 100644
--- 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;