SL-10190: Introduce LLCoros::saveException() and rethrow().

This mechanism uses a queue of std::exception_ptrs to transport an (otherwise)
uncaught exception from a terminated coroutine to the thread's main fiber. The
main loop calls LLCoros::rethrow() just after giving some cycles to ready
coroutines that frame.

# Conflicts:
#	indra/llcommon/llcoros.cpp
#	indra/llcommon/llcoros.h
#	indra/newview/llappviewer.cpp

1 files changed, 22 insertions, 3 deletions

diff --git a/indra/llcommon/llcoros.cpp b/indra/llcommon/llcoros.cpp
index 6a534951ff..a182d305e8 100644
--- a/indra/llcommon/llcoros.cpp
+++ b/indra/llcommon/llcoros.cpp
@@ -35,6 +35,7 @@
 // STL headers
 // std headers
 #include <atomic>
+#include <stdexcept>
 // external library headers
 #include <boost/bind.hpp>
 #include <boost/fiber/fiber.hpp>
@@ -214,6 +215,22 @@ std::string LLCoros::logname()
     return data.mName.empty()? data.getKey() : data.mName;
 }
 
+void LLCoros::saveException(const std::string& name, std::exception_ptr exc)
+{
+    mExceptionQueue.emplace(name, exc);
+}
+
+void LLCoros::rethrow()
+{
+    if (! mExceptionQueue.empty())
+    {
+        ExceptionData front = mExceptionQueue.front();
+        mExceptionQueue.pop();
+        LL_WARNS("LLCoros") << "Rethrowing exception from coroutine " << front.name << LL_ENDL;
+        std::rethrow_exception(front.exception);
+    }
+}
+
 void LLCoros::setStackSize(S32 stacksize)
 {
     LL_DEBUGS("LLCoros") << "Setting coroutine stack size to " << stacksize << LL_ENDL;
@@ -330,9 +347,11 @@ void LLCoros::toplevel(std::string name, callable_t callable)
     }
     catch (...)
     {
-        // Any OTHER kind of uncaught exception will cause the viewer to
-        // crash, hopefully informatively.
-        CRASH_ON_UNHANDLED_EXCEPTION(STRINGIZE("coroutine " << name));
+        // Stash any OTHER kind of uncaught exception in the rethrow() queue
+        // to be rethrown by the main fiber.
+        LL_WARNS("LLCoros") << "Capturing uncaught exception in coroutine "
+                            << name << LL_ENDL;
+        LLCoros::instance().saveException(name, std::current_exception());
     }
 }