openresty/luajit2 - OpenResty's maintained branch of LuaJIT.
This is the official OpenResty branch of LuaJIT. It is not to be considered a fork, since we still regularly synchronize changes from the upstream LuaJIT project (https://github.com/LuaJIT/LuaJIT).
Additionally to synchronizing upstream changes, we introduce our own changes which haven't been merged yet (or never will be). This document describes those changes that are specific to this branch.
syntax: res = isempty(tab)
Returns true
when the given Lua table contains neither non-nil array elements
nor non-nil key-value pairs, or false
otherwise.
This API can be JIT compiled.
Usage:
local isempty = require "table.isempty"
print(isempty({})) -- true
print(isempty({nil, dog = nil})) -- true
print(isempty({"a", "b"})) -- false
print(isempty({nil, 3})) -- false
print(isempty({cat = 3})) -- false
syntax: res = isarray(tab)
Returns true
when the given Lua table is a pure array-like Lua table, or
false
otherwise.
Empty Lua tables are treated as arrays.
This API can be JIT compiled.
Usage:
local isarray = require "table.isarray"
print(isarray{"a", true, 3.14}) -- true
print(isarray{"dog" = 3}) -- false
print(isarray{}) -- true
syntax: n = nkeys(tab)
Returns the total number of elements in a given Lua table (i.e. from both the array and hash parts combined).
This API can be JIT compiled.
Usage:
local nkeys = require "table.nkeys"
print(nkeys({})) -- 0
print(nkeys({ "a", nil, "b" })) -- 2
print(nkeys({ dog = 3, cat = 4, bird = nil })) -- 2
print(nkeys({ "a", dog = 3, cat = 4 })) -- 3
syntax: t = clone(tab)
Returns a shallow copy of the given Lua table.
This API can be JIT compiled.
Usage:
local clone = require "table.clone"
local x = {x=12, y={5, 6, 7}}
local y = clone(x)
... use y ...
Note: We observe 7% over-all speedup in the edgelang-fan compiler's compiling speed whose Lua is generated by the fanlang compiler.
Note bis: Deep cloning is planned to be supported by adding true
as a
second argument.
syntax: state = jit.prngstate(state?)
Returns (and optionally sets) the current PRNG state (a Lua number) currently used by the JIT compiler.
When the state
argument is non-nil, it is expected to be a number, and will
override the current PRNG state.
Usage:
local state = jit.prngstate()
local newstate = jit.prngstate(123456)
Note: This API has no effect if LuaJIT is compiled with
-DLUAJIT_DISABLE_JIT
, and will return 0
.
syntax: exdata = th_exdata(data?)
This API allows for embedding user data into a thread (lua_State
).
The retrieved exdata
value on the Lua land is represented as a cdata object
of the ctype void*
.
As of this version, retrieving the exdata
(i.e. th_exdata()
without any
argument) can be JIT compiled.
Usage:
local th_exdata = require "thread.exdata"
th_exdata(0xdeadbeefLL) -- set the exdata of the current Lua thread
local exdata = th_exdata() -- fetch the exdata of the current Lua thread
Also available are the following public C API functions for manipulating
exdata
on the C land:
void lua_setexdata(lua_State *L, void *exdata);
void *lua_getexdata(lua_State *L);
The exdata
pointer is initialized to NULL
when the main thread is created.
Any child Lua thread will inherit its parent's exdata
, but still can override
it.
Note: This API will not be available if LuaJIT is compiled with
-DLUAJIT_DISABLE_FFI
.
Note bis: This API is used internally by the OpenResty core, and it is strongly discouraged to use it yourself in the context of OpenResty.
The macros described in this section have been added to this branch.
In the luajit.h
header file, a new macro OPENRESTY_LUAJIT
was defined to
help distinguishing this OpenResty-specific branch of LuaJIT.
We use more appressive default JIT compiler options to help large OpenResty Lua applications.
The following jit.opt
options are used by default:
maxtrace=8000
maxrecord=16000
minstitch=3
maxmcode=40960 -- in KB
This optimization only applies to Intel CPUs supporting the SSE 4.2 instruction
sets. For such CPUs, and when this branch is compiled with -msse4.2
, the
string hashing function used for strings interning will be based on an
optimized crc32 implementation (see lj_str_new()
).
This optimization still provides constant-time hashing complexity (O(n)
), but
makes hash collision attacks harder for strings up to 127 bytes of size.
The bytecode option L
was added to display Lua sources line numbers.
For example, luajit -bL -e 'print(1)'
now produces bytecode dumps like below:
-- BYTECODE -- "print(1)":0-1
0001 [1] GGET 0 0 ; "print"
0002 [1] KSHORT 1 1
0003 [1] CALL 0 1 2
0004 [1] RET0 0 1
The [N]
column corresponds to the Lua source line number. For example, [1]
means "the first source line".
The bytecode option l
was updated to display the constant tables of each Lua
prototype.
For example, luajit -bl a.lua'
now produces bytecode dumps like below:
-- BYTECODE -- a.lua:0-48
KGC 0 "print"
KGC 1 "hi"
KGC 2 table
KGC 3 a.lua:17
KN 1 1000000
KN 2 1.390671161567e-309
...
- Increased the maximum number of allowed upvalues from 60 to 120.
- Various important bugfixes in the JIT compiler and Lua VM which have not been merged in upstream LuaJIT.
- Removed the GCC 4 requirement for x86 on older systems such as Solaris i386.
- In the
Makefile
file, make sure we always install the symlink for "luajit" even for alpha or beta versions. - Applied a patch to fix DragonFlyBSD compatibility. Note: this is not an officially supported target.
- Turned off string comparison optimizations for 64-bit architectures when the
build option
LUAJIT_USE_VALGRIND
is specified. LuaJIT is now (almost) valgrind clean. - feature: jit.dump: output Lua source location after every BC.
- feature: added internal memory-buffer-based trace entry/exit/start-recording
event logging, mainly for debugging bugs in the JIT compiler. it requires
-DLUA_USE_TRACE_LOGS
when building LuaJIT. - feature: save
g->jit_base
tog->saved_jit_base
beforelj_err_throw
clearsg->jit_base
which makes it impossible to get Lua backtrace in such states.
LuaJIT is a Just-In-Time (JIT) compiler for the Lua programming language.
Project Homepage: https://luajit.org/
LuaJIT is Copyright (C) 2005-2019 Mike Pall.
Additional patches for OpenResty are copyrighted by Yichun Zhang and OpenResty Inc.:
Copyright (C) 2017-2019 Yichun Zhang. All rights reserved.
Copyright (C) 2017-2019 OpenResty Inc. All rights reserved.
LuaJIT is free software, released under the MIT license. See full Copyright Notice in the COPYRIGHT file or in luajit.h.
Documentation for the official LuaJIT is available in HTML format. Please point your favorite browser to:
doc/luajit.html