链接到 Lua 5.2.4 的问题，即使在内联编译源代码时也是如此

Question

我有一个文件configuration.cpp:

#include "configuration.hpp"

struct game_config* get_game_config(lua_State *L, char* script)
{
    debug("Attempting to load configuration from %s", script);
    // Execute the script
    luaL_dofile(L, script);

    // The environment should now be prepped, we can get the config variables
    struct game_config* game_config;

    lua_getglobal(L, "WINDOW_WIDTH");
    game_config->screen_width = lua_tointeger(L, -1);
    lua_getglobal(L, "WINDOW_HEIGHT");
    game_config->screen_height = lua_tointeger(L, -1);
    lua_getglobal(L, "GAME_TITLE");
    game_config->game_title = lua_tostring(L, -1);

    debug("Loaded config for %s, at %dx%d", game_config->game_title, game_config->screen_width, game_config->screen_height);

    return game_config;
};

其中包括 configuration.hpp:

#ifndef CONFIGURATION_HPP_INCLUDED
#define CONFIGURATION_HPP_INCLUDED

#include "common.hpp"
#include "scripting.hpp"

// Data structures

struct game_config {
    int screen_width;
    int screen_height;

    const char *game_title;
};

/*
 * get_config
 * run a script and retrieve configuration data from it
 */

struct game_config *get_game_config(lua_State*, char *);

#endif // CONFIGURATION_HPP_INCLUDED

其中包括 scripting.hpp，其中以下行导入 Lua5.2:

#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"

当我将这些行添加到 configuration.cpp 时，程序编译并运行。但是，当它们在任何其他文件中时（configuration.hpp、scripting.hpp），它不会：

||=== Build: debug in rpfreedom (compiler: GNU GCC Compiler) ===|
src/configuration.cpp||In function ‘game_config* get_game_config(lua_State*, char*)’:|
src/configuration.cpp|13|warning: ‘game_config’ is used uninitialized in this function [-Wuninitialized]|
src/main.cpp||In function ‘int main()’:|
src/main.cpp|13|warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]|
build/debug/configuration.o||In function `get_game_config(lua_State*, char*)':|
/home/leo/projects/rpfreedom/src/configuration.cpp|7|undefined reference to `luaL_loadfilex(lua_State*, char const*, char const*)'|
/home/leo/projects/rpfreedom/src/configuration.cpp|7|undefined reference to `lua_pcallk(lua_State*, int, int, int, int, int (*)(lua_State*))'|
/home/leo/projects/rpfreedom/src/configuration.cpp|12|undefined reference to `lua_getglobal(lua_State*, char const*)'|
/home/leo/projects/rpfreedom/src/configuration.cpp|13|undefined reference to `lua_tointegerx(lua_State*, int, int*)'|
/home/leo/projects/rpfreedom/src/configuration.cpp|14|undefined reference to `lua_getglobal(lua_State*, char const*)'|
/home/leo/projects/rpfreedom/src/configuration.cpp|15|undefined reference to `lua_tointegerx(lua_State*, int, int*)'|
/home/leo/projects/rpfreedom/src/configuration.cpp|16|undefined reference to `lua_getglobal(lua_State*, char const*)'|
/home/leo/projects/rpfreedom/src/configuration.cpp|17|undefined reference to `lua_tolstring(lua_State*, int, unsigned long*)'|
build/debug/scripting.o||In function `scripting_init()':|
/home/leo/projects/rpfreedom/src/scripting.cpp|7|undefined reference to `luaL_newstate()'|
/home/leo/projects/rpfreedom/src/scripting.cpp|20|undefined reference to `lua_settop(lua_State*, int)'|
build/debug/scripting.o||In function `scripting_report_errors(lua_State*, int)':|
/home/leo/projects/rpfreedom/src/scripting.cpp|30|undefined reference to `lua_tolstring(lua_State*, int, unsigned long*)'|
/home/leo/projects/rpfreedom/src/scripting.cpp|31|undefined reference to `lua_settop(lua_State*, int)'|
build/debug/scripting.o:(.rodata+0x88)||undefined reference to `luaopen_base(lua_State*)'|
Makefile|203|recipe for target 'bin/debug/rpfreedom' failed|
Makefile|160|recipe for target 'debug' failed|
||=== Build failed: 15 error(s), 2 warning(s) (0 minute(s), 1 second(s)) ===|

显然，包含 configuration.hpp 是有效的，因为没有关于 game_config 结构的错误，它在那里定义；递归包含也是如此，因为 debug() 宏遵循路径 debug.hpp -> common.hpp -> configuration.hpp -> configuration.cpp。那么，为什么 Lua header 文件的 #includes 不能以类似的方式工作？

我决定调查；我运行g++ -Iinclude -I/usr/include/lua5.2 -E src/configuration.cpp| grep lua_getglobal查看预处理器输出，结果发现……是的。连同它在源代码中的使用，该命令 returns:

extern void (lua_getglobal) (lua_State *L, const char *var);

所以，我不知道发生了什么。

编辑：原来我必须在我的 #include 周围为 Lua 做 extern C {}。但是，现在，仅在 configuration.hpp 中（不在 scripting.hpp 中，其中包含 Lua header）我收到另一个错误：

include/configuration.hpp:21:37: error: ‘lua_State’ was not declared in this scope
 struct game_config *get_game_config(lua_State*, char *);

但是，lua_State在scripting.cpp和scripting.hpp中的使用不受影响。

编辑 2：显然，推荐的嵌入 Lua 5.2 的方法是将其与您的项目一起编译，因为它非常小，所以我这样做了。然而，即使我的 Makefile 生成的 link 命令清楚地 links 我的所有 object 文件和 Lua object 文件：

g++ build/release/configuration.o build/release/lua5.2.4/lparser.c.o build/release/lua5.2.4/lcode.c.o build/release/lua5.2.4/lundump.c.o build/release/lua5.2.4/lzio.c.o build/release/lua5.2.4/ldo.c.o build/release/lua5.2.4/lapi.c.o build/release/lua5.2.4/lgc.c.o build/release/lua5.2.4/lfunc.c.o build/release/lua5.2.4/ldump.c.o build/release/lua5.2.4/ltable.c.o build/release/lua5.2.4/lcorolib.c.o build/release/lua5.2.4/loslib.c.o build/release/lua5.2.4/liolib.c.o build/release/lua5.2.4/ltm.c.o build/release/lua5.2.4/lmem.c.o build/release/lua5.2.4/lctype.c.o build/release/lua5.2.4/lauxlib.c.o build/release/lua5.2.4/ldebug.c.o build/release/lua5.2.4/lobject.c.o build/release/lua5.2.4/loadlib.c.o build/release/lua5.2.4/linit.c.o build/release/lua5.2.4/lmathlib.c.o build/release/lua5.2.4/llex.c.o build/release/lua5.2.4/lstate.c.o build/release/lua5.2.4/lopcodes.c.o build/release/lua5.2.4/lstrlib.c.o build/release/lua5.2.4/lbaselib.c.o build/release/lua5.2.4/ltablib.c.o build/release/lua5.2.4/ldblib.c.o build/release/lua5.2.4/lbitlib.c.o build/release/lua5.2.4/lvm.c.o build/release/lua5.2.4/lstring.c.o build/release/scripting.o build/release/main.o  -L/usr/lib/x86_64-linux-gnu -Lm -Ldl -lsfml-graphics -lsfml-window -lsfml-audio -lsfml-network -lsfml-system   -o bin/release/rpfreedom

我遇到了和之前一样的 linker 错误。

linker 的参数顺序重要吗？

Answer 1

您显示的错误消息似乎来自您的 linker，而不是编译器。

一切都已成功包含。一切都已成功编译。但是 link 失败了，因为某些必需的库没有 link 编辑。

注意错误信息参考：

build/debug/configuration.o
...
build/debug/scripting.o
...

... 而不是您的源代码（错误中提到的 cpp 具有误导性，它们实际上是从您的 .o 文件中的调试信息中提取的）。并且错误消息通常是来自 linker.

的错误消息

你的源代码没问题。您需要修复您的 makefile。

Answer 2

好吧，你的第一个警告正是编译器告诉你的。你的代码是这样的：

// The environment should now be prepped, we can get the config variables
struct game_config* game_config;

lua_getglobal(L, "WINDOW_WIDTH");
game_config->screen_width = lua_tointeger(L, -1);

警告是：

‘game_config’ is used uninitialized in this function.

在访问 screen_width 之前，您尚未将指针 game_config 设置为指向任何内容。也许您需要将其设置为 new game_config()。我更愿意在堆栈上创建一个并按值return它：

game_config config;
lua_getglobal(L, "WINDOW_WIDTH");
config.screen_width = lua_tointeger(L, -1);
...
return config;

无论哪种方式，将 game_title 设为 std::string 可能比 const char * 更好。

Answer 3

我最终通过自己编译一个静态 Lua (liblua.a)、创建一个 lib/ 目录并将 -Llib -llua 添加到我的链接器行来纠正这个问题。这将需要额外的努力来实现跨平台，但就目前而言，没问题。

链接到 Lua 5.2.4 的问题，即使在内联编译源代码时也是如此

Problems linking to Lua 5.2.4, even when compiling sources inline

c

c++

linker

lua

linker-errors