From c603cba2c23c7a7ef2afba6dabed3c049827c905 Mon Sep 17 00:00:00 2001
From: stbuehler <stbuehler@152afb58-edef-0310-8abb-c4023f1b3aa9>
Date: Mon, 26 Oct 2009 15:12:18 +0000
Subject: mod_magnet: add traceback for printing lua errors

git-svn-id: svn://svn.lighttpd.net/lighttpd/trunk@2682 152afb58-edef-0310-8abb-c4023f1b3aa9
---
 NEWS             |  1 +
 src/mod_magnet.c | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 06d25926..afc46534 100644
--- a/NEWS
+++ b/NEWS
@@ -152,6 +152,7 @@ NEWS
   * Fix mod_cgi hang on "crash-before-header-sent" bug
   * Set content-length in mod_compress (fixes #2089, thx liming)
   * Mark recv-queue closed if backend connection got closed in mod_proxy_core (fixes #2090, thx liming)
+  * mod_magnet: add traceback for printing lua errors
 
 - 1.5.0-r19.. -
   * -F option added for spawn-fcgi
diff --git a/src/mod_magnet.c b/src/mod_magnet.c
index 48b33f00..d1260396 100644
--- a/src/mod_magnet.c
+++ b/src/mod_magnet.c
@@ -695,9 +695,36 @@ static int magnet_attach_content(server *srv, connection *con, plugin_data *p, l
 	return 0;
 }
 
+static int traceback (lua_State *L) {
+	if (!lua_isstring(L, 1))  /* 'message' not a string? */
+		return 1;  /* keep it intact */
+	lua_getfield(L, LUA_GLOBALSINDEX, "debug");
+	if (!lua_istable(L, -1)) {
+		lua_pop(L, 1);
+		return 1;
+	}
+	lua_getfield(L, -1, "traceback");
+	if (!lua_isfunction(L, -1)) {
+		lua_pop(L, 2);
+		return 1;
+	}
+	lua_pushvalue(L, 1);  /* pass error message */
+	lua_pushinteger(L, 2);  /* skip this function and traceback */
+	lua_call(L, 2, 1);  /* call debug.traceback */
+	return 1;
+}
+
+static int push_traceback(lua_State *L, int narg) {
+	int base = lua_gettop(L) - narg;  /* function index */
+	lua_pushcfunction(L, traceback);
+	lua_insert(L, base);
+	return base;
+}
+
 static handler_t magnet_attract(server *srv, connection *con, plugin_data *p, buffer *name) {
 	lua_State *L;
 	int lua_return_value = -1;
+	int errfunc;
 	/* get the script-context */
 
 
@@ -812,7 +839,9 @@ static handler_t magnet_attract(server *srv, connection *con, plugin_data *p, bu
 
 	lua_setfenv(L, -2); /* on the stack should be a modified env (sp -= 1) */
 
-	if (lua_pcall(L, 0, 1, 0)) {
+	errfunc = push_traceback(L, 0);
+	if (lua_pcall(L, 0, 1, errfunc)) {
+		lua_remove(L, errfunc);
 		log_error_write(srv, __FILE__, __LINE__,
 			"ss",
 			"lua_pcall():",
@@ -825,6 +854,7 @@ static handler_t magnet_attract(server *srv, connection *con, plugin_data *p, bu
 
 		return HANDLER_FINISHED;
 	}
+	lua_remove(L, errfunc);
 
 	/* we should have the function-copy and the return value on the stack */
 	assert(lua_gettop(L) == 2);
-- 
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