Question

我有一个配置文件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;
};

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

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，程序将编译并运行。但是，当它们在任何其他文件（configuration.hpp，scripting.hpp）中时，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，这是在那里定义的; ditto for recursive includes，因为debug（）宏遵循路径debug.hpp -> common.hpp -> configuration.hpp -> configuration.cpp。那么，为什么Lua头文件的#includes不能以类似的方式工作呢？

我决定调查;我运行g++ -Iinclude -I/usr/include/lua5.2 -E src/configuration.cpp| grep lua_getglobal来查看预处理器输出，结果是......它们是。除了在源代码中的使用外，该命令还会返回：

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

所以，我不知道发生了什么。

编辑：事实证明我必须在extern C {}周围为Lua做#include。但是，现在，仅在configuration.hpp中（不在包含Lua头的scripting.hpp中）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，在scripting.cpp和scripting.hpp中使用lua_State不会受到影响。

编辑2：显然，嵌入Lua 5.2的推荐方法是用你的项目编译它，因为它非常小，所以我这样做了。但是，即使我的Makefile生成的链接命令清楚地链接了我的所有目标文件和Lua目标文件：

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

我得到了与之前相同的链接器错误。

链接器的参数顺序是否重要？

Answer 1

您显示的错误消息似乎来自您的链接器，而不是编译器。

一切都成功包括在内。一切都成功编译。但链接失败了，因为某些必需的库没有链接。

请注意错误消息引用：

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

...而不是您的源代码（错误中提到的cpp是误导性的，它们实际上是从.o文件中的调试信息中提取的）。错误消息通常是链接器发出的错误消息。

您的源代码很好。你需要修复你的makefile。

Answer 2

我最后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了这个问题。这需要额外的努力来制作跨平台，但是现在，这很好。

Answer 3

好吧，你的第一个警告正是编译器告诉你的。你的代码是：

// 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);

并且警告是：

‘game_config’ is used uninitialized in this function.

在您访问game_config之前，您尚未将指针screen_width设置为指向任何内容。也许您需要将其设置为new game_config()。我宁愿在堆栈上创建一个并按值返回：

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

无论哪种方式，最好将game_title设为std::string而不是const char *。

链接到Lua 5.2.4的问题，即使在内联编译源

3 个答案: