From 9b2de5f4fcef8d77873bbda7db7f6e6d4f596154 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Sat, 30 Mar 2019 14:35:07 -0700
Subject: [PATCH] ircd::json::stack: Add conditional exception rollback toggle.

---
 include/ircd/json/stack.h | 8 ++++++--
 ircd/json.cc              | 9 +++++++--
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/include/ircd/json/stack.h b/include/ircd/json/stack.h
index c51c7d4a7..56bfe9778 100644
--- a/include/ircd/json/stack.h
+++ b/include/ircd/json/stack.h
@@ -248,7 +248,7 @@ struct ircd::json::stack::const_chase
 /// rollback() pitfall.
 ///
 /// - Destruction under an exception is equivalent to a decommit() and will
-/// perform a rollback().
+/// perform a rollback() if exception_rollback is set.
 ///
 /// Flushes are avoided under the scope of a checkpoint, but they are still
 /// forced if the json::stack buffer fills up. In this case all active
@@ -261,6 +261,7 @@ struct ircd::json::stack::checkpoint
 	size_t point {0};
 	size_t vc {0};
 	bool committed {true};
+	bool exception_rollback {true};
 
   public:
 	bool committing() const;     ///< When false, destructor will rollback()
@@ -268,7 +269,10 @@ struct ircd::json::stack::checkpoint
 	bool decommit();             ///< Sets committing() to false.
 	bool rollback();             ///< Performs rollback of buffer.
 
-	checkpoint(stack &s, const bool &committed = true);
+	checkpoint(stack &s,
+	           const bool &committed = true,
+	           const bool &exception_rollback = true);
+
 	checkpoint(checkpoint &&) = delete;
 	checkpoint(const checkpoint &) = delete;
 	~checkpoint() noexcept;
diff --git a/ircd/json.cc b/ircd/json.cc
index 723387643..e9050bfef 100644
--- a/ircd/json.cc
+++ b/ircd/json.cc
@@ -1459,7 +1459,8 @@ ircd::json::stack::member::_post_append()
 //
 
 ircd::json::stack::checkpoint::checkpoint(stack &s,
-                                          const bool &committed)
+                                          const bool &committed,
+                                          const bool &exception_rollback)
 :s{&s}
 ,pc{s.cp}
 ,point
@@ -1486,6 +1487,10 @@ ircd::json::stack::checkpoint::checkpoint(stack &s,
 {
 	committed
 }
+,exception_rollback
+{
+	exception_rollback
+}
 {
 	s.cp = this;
 }
@@ -1496,7 +1501,7 @@ noexcept
 	if(!s)
 		return;
 
-	if(std::uncaught_exceptions())
+	if(std::uncaught_exceptions() && exception_rollback)
 		decommit();
 
 	if(!committing())