Lua-gdb

gdb extension for lua5.3+.

tested on GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1.

Features

Pretty printer

• struct TValue
• struct TString
• struct Table
• struct LClosure
• struct CClosure
• struct lua_State

Command

• luacoroutines [L]

List all coroutines. Without arguments, uses the current value of "L" as the lua_State*. You can provide an alternate lua_State as the first argument.

• luastack [L]

Prints values on the Lua C stack. Without arguments, uses the current value of "L" as the lua_State*. You can provide an alternate lua_State as the first argument.

• luatraceback [L]

Dumps Lua execution stack, as debug.traceback() does. Without arguments, uses the current value of "L" as the lua_State*. You can provide an alternate lua_State as the first argument.

• luagetlocal [L [f]]

Print all variables of the function at level 'f' of the stack 'coroutine'. With no arguments, Dump all variables of the current funtion in the stack of 'L'.

Usage (step by step)

• compile lua with debug symbols

cd lua-5.3.4
make linux CFLAGS=-g

• start gdb

gdb lua-5.3.4/src/lua

• set a breakpoint

(gdb) break os_time
Breakpoint 1 at 0x42c9fe: file loslib.c, line 324.

• run examples/dbg.lua

(gdb) run examples/dbg.lua
Starting program: /usr/local/bin/lua examples/dbg.lua

Breakpoint 1, os_time (L=0x64b9c8) at loslib.c:324
324     static int os_time (lua_State *L) {

will hit the breakpoint os_time.

• load the extension

(gdb) source lua-gdb.py
Loading Lua Runtime support.

• list all coroutines

(gdb) luacoroutines
m <coroutine 0x645018> = {[source] = [C]:-1, [func] = 0x427ff9 <luaB_coresume>}
  <coroutine 0x64b9c8> = {[source] = [C]:-1, [func] = 0x42c9f2 <os_time>}
  <coroutine 0x645638> = {[source] = [C]:-1, [func] = ?}

• dump stack

(gdb) luastack 0x64b9c8
#0      0x64bb30        <os_time>
#1      0x64bb20        2
#2      0x64bb10        5
#3      0x64bb00        10
#4      0x64baf0        "kkk"
#5      0x64bae0        1
#6      0x64bad0        "nil"
#7      0x64bac0        "nil"
#8      0x64bab0        <lclosure 0x64b920> = {[file] = "@examples/dbg.lua", [linestart] = 17, [lineend] = 20, [nupvalues] = 1 '\001'}

• dump traceback

(gdb) luatraceback 0x64b9c8
stack traceback:
        [C]:-1: in 0x42c9f2 <os_time>
        "@examples/dbg.lua":19: in ?

• list all variables of a closure in the traceback

(gdb) luagetlocal 0x64b9c8 1
call info: "@examples/dbg.lua":19: in ?
        upval _ENV = 3.2627937150349253e-317
        ..... (*vararg) = 1
        ..... (*vararg) = "kkk"
        local x = 10
        local i = 5
        local n = 2

• enjoy it!