Lua-5.3-style APIs for Lua 5.2 and 5.1.

This is a small module that aims to make it easier to write code in a Lua-5.3-style that is compatible with Lua 5.1, Lua 5.2, and Lua 5.3. This does not make Lua 5.2 (or even Lua 5.1) entirely compatible with Lua 5.3, but it brings the API closer to that of Lua 5.3.

It includes:

• For writing Lua: The Lua module compat53, which can be require'd from Lua scripts and run in Lua 5.1, 5.2, and 5.3, including a backport of the utf8 module, the 5.3 table module, and the string packing functions straight from the Lua 5.3 sources.
• For writing C: A C header and file which can be linked to your Lua module written in C, providing some functions from the C API of Lua 5.3 that do not exist in Lua 5.2 or 5.1, making it easier to write C code that compiles with all three versions of liblua.

require("compat53")

compat53 makes changes to your global environment and does not return a meaningful return value, so the usual idiom of storing the return of require in a local variable makes no sense.

When run under Lua 5.3, this module does nothing.

When run under Lua 5.2 or 5.1, it replaces some of your standard functions and adds new ones to bring your environment closer to that of Lua 5.3. It also tries to load the backported utf8, table, and string packing modules automatically. If unsuccessful, pure Lua versions of the new table functions are used as a fallback, and Roberto's struct library is tried for string packing.

There are two ways of adding the C API compatibility functions/macros to your project:

• If COMPAT53_PREFIX is not #defined, compat-5.3.h #includes compat-5.3.c, and all functions are made static. You don't have to compile/link/add compat-5.3.c yourself. This is useful for one-file projects.
• If COMPAT53_PREFIX is #defined, all exported functions are renamed behind the scenes using this prefix to avoid linker conflicts with other code using this package. This doesn't change the way you call the compatibility functions in your code. You have to compile and link compat-5.3.c to your project yourself. You can change the way the functions are exported using the COMPAT53_API macro (e.g. if you need some __declspec magic).

• the utf8 module backported from the Lua 5.3 sources
• string.pack, string.packsize, and string.unpack from the Lua 5.3 sources or from the struct module. (struct is not 100% compatible to Lua 5.3's string packing!)
• math.maxinteger and math.mininteger, math.tointeger, math.type, and math.ult
• ipairs respects __index metamethod
• table.move
• table library respects metamethods

For Lua 5.1 additionally:

• load and loadfile accept mode and env parameters
• table.pack and table.unpack
• string patterns may contain embedded zeros
• string.rep accepts sep argument
• string.format calls tostring on arguments for %s
• math.log accepts base argument
• xpcall takes additional arguments
• pcall and xpcall can execute functions that yield
• pairs respects __pairs metamethod
• rawlen (but # still doesn't respect __len for tables)
• package.searchers as alias for package.loaders
• package.searchpath
• coroutine functions dealing with the main coroutine
• coroutine.create accepts functions written in C
• return code of os.execute
• io.write and file:write return file handle
• io.lines and file:lines accept format arguments (like io.read)
• debug.setmetatable returns object
• debug.getuservalue and debug.setuservalue

• lua_KContext
• lua_KFunction
• lua_dump (extra strip parameter, ignored)
• lua_getfield (return value)
• lua_geti and lua_seti
• lua_getglobal (return value)
• lua_getmetafield (return value)
• lua_gettable (return value)
• lua_getuservalue and lua_setuservalue (limited compatibility)
• lua_isinteger
• lua_numbertointeger
• lua_callk and lua_pcallk (limited compatibility)
• lua_rawget and lua_rawgeti (return values)
• lua_rawgetp and lua_rawsetp
• luaL_requiref (now checks package.loaded first)
• lua_rotate
• lua_stringtonumber

For Lua 5.1 additionally:

• LUA_OK
• LUA_OP* macros for lua_arith and lua_compare
• lua_Unsigned
• luaL_Stream
• LUA_FILEHANDLE
• lua_absindex
• lua_arith
• lua_compare
• lua_len, lua_rawlen, and luaL_len
• lua_copy
• lua_pushglobaltable
• luaL_testudata
• luaL_setfuncs, luaL_newlibtable, and luaL_newlib
• luaL_setmetatable
• luaL_getsubtable
• luaL_traceback
• luaL_fileresult
• luaL_checkversion (with empty body, only to avoid compile errors)
• luaL_tolstring
• luaL_buffinitsize, luaL_prepbuffsize, and luaL_pushresultsize
• lua_pushunsigned, lua_tounsignedx, lua_tounsigned, luaL_checkunsigned, luaL_optunsigned, if LUA_COMPAT_APIINTCASTS is defined.

• bit operators
• integer division operator
• utf8 escape sequences
• 64 bit integers
• coroutine.isyieldable
• Lua 5.1: _ENV, goto, labels, ephemeron tables, etc. See lua-compat-5.2 for a detailed list.
• the following C API functions/macros:
  • lua_isyieldable
  • lua_getextraspace
  • lua_arith (new operators missing)
  • lua_push(v)fstring (new formats missing)
  • lua_upvalueid (5.1)
  • lua_upvaluejoin (5.1)
  • lua_version (5.1)
  • lua_yieldk (5.1)
  • luaL_execresult (5.1)
  • luaL_loadbufferx (5.1)
  • luaL_loadfilex (5.1)

The emulation of lua_(p)callk for previous Lua versions is not 100% perfect, because the continuation functions in Lua 5.2 have different signatures than the ones in Lua 5.3 (and Lua 5.1 doesn't have continuation functions at all). But with the help of a small macro the same code can be used for all three Lua versions (the 5.1 version won't support yielding though).

Original Lua 5.3 code (example adapted from the Lua 5.3 manual):

static int k (lua_State *L, int status, lua_KContext ctx) {
  ...  /* code 2 */
}

int original_function (lua_State *L) {
  ...     /* code 1 */
  return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1);
}

Portable version:

LUA_KFUNCTION( k ) {
  ...  /* code 2; parameters L, status, and ctx available here */
}

int original_function (lua_State *L) {
  ...     /* code 1 */
  return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1);
}

• For Lua-5.2-style APIs under Lua 5.1, see lua-compat-5.2, which also is the basis for most of the code in this project.
• For Lua-5.1-style APIs under Lua 5.0, see Compat-5.1

This package contains code written by:

• The Lua Team
• Philipp Janda (@siffiejoe)
• Tomás Guisasola Gorham (@tomasguisasola)
• Hisham Muhammad (@hishamhm)
• Renato Maia (@renatomaia)