From f6e8301932ce1bb1c059826ded8807e7f8cdfc79 Mon Sep 17 00:00:00 2001
From: Daniel Silverstone <daniel.silverstone@codethink.co.uk>
Date: Mon, 13 Aug 2012 17:28:15 +0100
Subject: SANDBOX: Update sandbox and wrapper so that we write to stderr (dead,
 but who cares) if an error propagates all the way out

---
 lib/supple/sandbox.lua | 12 +++++++++++-
 src/wrapper.c          |  8 +++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/lib/supple/sandbox.lua b/lib/supple/sandbox.lua
index bcb2cb8..f4025bc 100644
--- a/lib/supple/sandbox.lua
+++ b/lib/supple/sandbox.lua
@@ -31,6 +31,8 @@ local load = load
 local setfenv = setfenv
 local gc = collectgarbage
 local unpack = unpack
+local xpcall = xpcall
+local traceback = debug.traceback
 
 local function set_limits(ltab)
    local count = ltab.count
@@ -162,6 +164,14 @@ local function run()
    return fn(comms._wait)
 end
 
+local function wrapper_run()
+   local ok, retcode = xpcall(run, traceback)
+   if not ok then
+      error(retcode)
+   end
+   return retcode
+end
+
 return {
-   run = run,
+   run = wrapper_run,
 }
diff --git a/src/wrapper.c b/src/wrapper.c
index 7cb52e3..d4f1412 100644
--- a/src/wrapper.c
+++ b/src/wrapper.c
@@ -68,7 +68,13 @@ main(int argc, char **argv)
 	parg.retcode = 0;
 	
 	success = lua_cpcall(L, &protected_main, &parg);
-	
+
+        if (success != 0) {
+		size_t l;
+		const char *s = lua_tolstring(L, 1, &l);
+		write(2, s, l);
+        }
+
 	lua_close(L);
 	
 	return ((success == 0) && (parg.retcode == 0)) ? EXIT_SUCCESS :
-- 
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