From 9aca31681a070ef9119e1bb4d7a60554100bc835 Mon Sep 17 00:00:00 2001
From: Brad Jorsch <bjorsch@wikimedia.org>
Date: Tue, 6 Feb 2018 16:07:11 -0500
Subject: [PATCH] LuaStandalone: Improve passing of numeric values

For integers from Lua to PHP, make sure they won't use exponential
notation that will confuse unserialize(), and pass the integer size from
PHP so Lua can know which numbers are representable as integers.

For doubles in both directions, increase the precision to avoid
truncation of the least significant bits.

Change-Id: Icfaff71cab0ee1aac04acf752d108049b5569380
---
 engines/LuaStandalone/LuaStandaloneEngine.php |  5 +++--
 engines/LuaStandalone/MWServer.lua            | 22 +++++++++++++------
 engines/LuaStandalone/mw_main.lua             |  2 +-
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/engines/LuaStandalone/LuaStandaloneEngine.php b/engines/LuaStandalone/LuaStandaloneEngine.php
index 728e3c05..bfc02da9 100644
--- a/engines/LuaStandalone/LuaStandaloneEngine.php
+++ b/engines/LuaStandalone/LuaStandaloneEngine.php
@@ -198,7 +198,8 @@ class Scribunto_LuaStandaloneInterpreter extends Scribunto_LuaInterpreter {
 			$options['luaPath'],
 			__DIR__ . '/mw_main.lua',
 			dirname( dirname( __DIR__ ) ),
-			$this->id
+			$this->id,
+			PHP_INT_SIZE
 		);
 		if ( php_uname( 's' ) == 'Linux' ) {
 			// Limit memory and CPU
@@ -560,7 +561,7 @@ class Scribunto_LuaStandaloneInterpreter extends Scribunto_LuaInterpreter {
 					}
 					throw new MWException( __METHOD__.': cannot convert non-finite number' );
 				}
-				return $var;
+				return sprintf( '%.17g', $var );
 			case 'string':
 				return '"' .
 					strtr( $var, [
diff --git a/engines/LuaStandalone/MWServer.lua b/engines/LuaStandalone/MWServer.lua
index c4d9fcf8..de4af3b1 100644
--- a/engines/LuaStandalone/MWServer.lua
+++ b/engines/LuaStandalone/MWServer.lua
@@ -1,11 +1,15 @@
 MWServer = {}
 
 --- Create a new MWServer object
-function MWServer:new( interpreterId )
+function MWServer:new( interpreterId, intSize )
 	interpreterId = tonumber( interpreterId )
 	if not interpreterId then
 		error( "bad argument #1 to 'MWServer:new' (must be a number or convertible to a number)", 2 )
 	end
+	intSize = tonumber( intSize )
+	if intSize ~= 4 and intSize ~= 8 then
+		error( "bad argument #2 to 'MWServer:new' (must be 4 or 8)", 2 )
+	end
 
 	obj = {
 		interpreterId = interpreterId,
@@ -16,6 +20,12 @@ function MWServer:new( interpreterId )
 		protectedEnvironments = {},
 		baseEnv = {}
 	}
+	if intSize == 4 then
+		obj.intMax = 2147483648
+	else
+		-- Lua can't represent most larger integers, so they may as well be sent to PHP as floats.
+		obj.intMax = 9007199254740992
+	end
 	setmetatable( obj, self )
 	self.__index = self
 
@@ -457,14 +467,12 @@ local serialize_replacements = {
 -- @param var The value.
 function MWServer:serialize( var )
 	local done = {}
-	local int_min = -2147483648
-	local int_max = 2147483647
 
 	local function isInteger( var )
 		return type(var) == 'number'
 			and math.floor( var ) == var
-			and var >= int_min
-			and var <= int_max
+			and var >= -self.intMax
+			and var < self.intMax
 	end
 
 	local function recursiveEncode( var, level )
@@ -473,9 +481,9 @@ function MWServer:serialize( var )
 			return 'N;'
 		elseif t == 'number' then
 			if isInteger(var) then
-				return 'i:' .. var .. ';'
+				return 'i:' .. string.format( '%d', var ) .. ';'
 			elseif var < math.huge and var > -math.huge then
-				return 'd:' .. var .. ';'
+				return 'd:' .. string.format( '%.17g', var ) .. ';'
 			elseif var == math.huge then
 				return 'd:INF;'
 			elseif var == -math.huge then
diff --git a/engines/LuaStandalone/mw_main.lua b/engines/LuaStandalone/mw_main.lua
index c8198a2d..651ab751 100644
--- a/engines/LuaStandalone/mw_main.lua
+++ b/engines/LuaStandalone/mw_main.lua
@@ -3,6 +3,6 @@ package.path = arg[1] .. '/engines/LuaStandalone/?.lua;' ..
 
 require('MWServer')
 require('mwInit')
-server = MWServer:new( arg[2] )
+server = MWServer:new( arg[2], arg[3] )
 server:execute()