c++ - Lua C API 内存泄漏？ (valgrind)

Question

我正在尝试编写一个嵌入了 Lua 的 C 程序。而且，我尝试了一个非常简单的程序来启动，它只是创建 Lua 上下文，然后销毁它:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
extern "C" {
    #include <lua.h>
    #include <lauxlib.h>
    #include <lualib.h>
}

int main(int argc, char *argv[]) {
    lua_State *L = lua_open();
    luaL_openlibs(L);

    lua_close(L);
    fprintf(stderr, "%s: %d\n", __FILE__, __LINE__);
    return(0);
}

我是这样编译的:(我实际上使用的是 Torch7，所以..)

g++ -c -g3 -O2 -Wall -Werror -I/usr/local/torch/install/include/ -fPIC pure_lua_test.C -o pure_lua_test.o
g++ -g3 -O2 -Wall -Werror -I/usr/local/torch/install/include/ -fPIC -o pure_lua_test pure_lua_test.o -L/usr/local/torch/install/lib/ -lluajit

当我自己运行它时，它会打印

pure_lua_test.C: 16

正如预期的那样，(就在返回之前)。

但是，当我用 valgrind 运行它时，(如 valgrind ./pure_lua_test )

我明白了

==9165== Memcheck, a memory error detector
==9165== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==9165== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
==9165== Command: ./pure_lua_test
==9165== 
==9165== Invalid read of size 4
==9165==    at 0x4E9EE97: lua_pushcclosure (in /usr/local/src/torch-2015-05-25/install/lib/libluajit.so)
==9165==    by 0x4EB4CDD: luaL_openlibs (in /usr/local/src/torch-2015-05-25/install/lib/libluajit.so)
==9165==    by 0x400700: main (pure_lua_test.C:13)
==9165==  Address 0x8 is not stack'd, malloc'd or (recently) free'd
==9165== 
==9165== 
==9165== Process terminating with default action of signal 11 (SIGSEGV)
==9165==  Access not within mapped region at address 0x8
==9165==    at 0x4E9EE97: lua_pushcclosure (in /usr/local/src/torch-2015-05-25/install/lib/libluajit.so)
==9165==    by 0x4EB4CDD: luaL_openlibs (in /usr/local/src/torch-2015-05-25/install/lib/libluajit.so)
==9165==    by 0x400700: main (pure_lua_test.C:13)
==9165==  If you believe this happened as a result of a stack
==9165==  overflow in your program's main thread (unlikely but
==9165==  possible), you can try to increase the size of the
==9165==  main thread stack using the --main-stacksize= flag.
==9165==  The main thread stack size used in this run was 8388608.
==9165== 
==9165== HEAP SUMMARY:
==9165==     in use at exit: 0 bytes in 0 blocks
==9165==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==9165== 
==9165== All heap blocks were freed -- no leaks are possible
==9165== 
==9165== For counts of detected and suppressed errors, rerun with: -v
==9165== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

有人知道这是怎么回事吗？为什么在 valgrind 中使用 SIGSEGV？这是我应该担心的事情吗？基本上，我希望验证我为 Torch 编写的插件没有内存泄漏......但是，如果它失败了，那么，我有点卡住了。

Answer 1

这个问题的原因似乎是 Valgrind，而不是 LuaJIT。 Valgrind 是 blocking MAP_32BIT which breaks LuaJIT .为了演示，在 lua_State * L 上添加对 NULL 的检查，您会看到它在 Valgrind 下运行时为 NULL，而非 NULL同时定期运行。

这是我对您的示例所做的修改:

if(L == NULL) {
    printf("Could not create luaL_newstate()\n");
} else {
    luaL_openlibs(L);
    lua_close(L);
    printf("I can create luaL_newstate fine!\n");
}

当我正常运行时:

$ ./pure_lua_test 
I can create luaL_newstate fine!

但是当我在 Valgrind 下运行它时:

$ valgrind ./pure_lua_test
==8211== Memcheck, a memory error detector
==8211== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==8211== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==8211== Command: ./pure_lua_test
==8211== 
Could not create luaL_newstate()
==8211== 

GDB 还报告应用程序正常退出:

(gdb) run
Starting program: /tmp/pure_lua_test 
I can create luaL_newstate fine!
[Inferior 1 (process 8621) exited normally]

这是一个完整的 MCVE:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
extern "C" {
        #include <lua.h>
        #include <lauxlib.h>
        #include <lualib.h>
}

int main(int argc, char *argv[]) {
    lua_State *L;
    L = luaL_newstate();

    if(L == NULL) {
        printf("Could not create luaL_newstate()\n");
    } else {
        luaL_openlibs(L);

        lua_close(L);
        printf("I can create luaL_newstate fine!\n");
    }

    return(0);
}

Here是一篇关于 MAP_32BIT 的好文章。希望这能以任何方式提供帮助。