util.xpcall, util.compat: Add non-hacky multi-argument xpcall() for Lua 5.1

util-src/GNUmakefile

@@ -6,7 +6,8 @@ CFLAGS+=-I$(LUA_INCDIR)
 INSTALL_DATA=install -m644
 TARGET?=../util/
 
-ALL=encodings.so hashes.so net.so pposix.so signal.so table.so ringbuffer.so time.so poll.so
+ALL=encodings.so hashes.so net.so pposix.so signal.so table.so \
+    ringbuffer.so time.so poll.so compat.so
 
 ifdef RANDOM
 ALL+=crand.so

util-src/compat.c

@@ -0,0 +1,29 @@
+
+#include <lua.h>
+#include <lauxlib.h>
+
+
+static int lc_xpcall (lua_State *L) {
+  int ret;
+  int n_arg = lua_gettop(L);
+  /* f, msgh, p1, p2... */
+  luaL_argcheck(L, n_arg >= 2, 2, "value expected");
+  lua_pushvalue(L, 1);  /* f to top */
+  lua_pushvalue(L, 2);  /* msgh to top */
+  lua_replace(L, 1); /* msgh to 1 */
+  lua_replace(L, 2); /* f to 2 */
+  /* msgh, f, p1, p2... */
+  ret = lua_pcall(L, n_arg - 2, LUA_MULTRET, 1);
+  lua_pushboolean(L, ret == 0);
+  lua_replace(L, 1);
+  return lua_gettop(L);
+}
+
+int luaopen_util_compat(lua_State *L) {
+	lua_createtable(L, 0, 2);
+	{
+		lua_pushcfunction(L, lc_xpcall);
+		lua_setfield(L, -2, "xpcall");
+	}
+	return 1;
+}

util/xpcall.lua

@@ -0,0 +1,9 @@
+local xpcall = xpcall;
+
+if select(2, xpcall(function (x) return x end, function () end,  "test")) ~= "test" then
+	xpcall = require"util.compat".xpcall;
+end
+
+return {
+	xpcall = xpcall;
+};