C - 在非结构或 union 中请求成员 ‘x’

Question

这个问题已经有答案了:

Why should we typedef a struct so often in C? (15 个回答)

已关闭 5 年前。

上下文:我正在尝试对一款名为 Grand Theft Auto V 的游戏进行一些修改。

我正在使用GET_ENTITY_COORDS获取游戏中实体坐标的函数:

static Inline struct Vector3 GET_ENTITY_COORDS(Entity entity, BOOL alive) {
    args[0] = entity;
    args[1] = alive;
    invokeNative(0x3FEF770D40960D5A);
    struct Vector3 vector3 = { *(float*)&rets[0], *(float*)&rets[1], *(float*)&rets[2] };
    return vector3;
}

这应该返回xPos , yPos和zPos .

<小时/>

现在这是我目前正在努力解决的代码:

#include "gta.h"

void invokeNative_s(u64 hash) {
    struct Native_s** g_Natives = (struct Native_s**)NativeTableAddress;
    struct Native_s* Natives = g_Natives[hash & 0xFF];
    while (Natives != 0) {
        for (unsigned int i = 0; i < Natives->NativeCount; i++) {
            if (Natives->NativeHashes[i] == hash) {
                ((void(*)(struct NativeArg_s*))Natives->NativeFunctions[i])((struct NativeArg_s*)FreeSpaceAddress);
                return;
            }
        }
        Natives = Natives->LastNativeTable;
    }
}

struct gtaVars_s {
    BOOL init;
    int frameCount;
};

static struct gtaVars_s *gtaVars = (struct gtaVars_s*)FreeSpaceAddress+0x100;

BOOL nativeHook() {
    if (!gtaVars->init) {
        nativeArg->ArgValues = args;
        nativeArg->ReturnValue = rets;
        gtaVars->frameCount = 0;
        gtaVars->init = TRUE;
    }

    int newFrameCount = GET_FRAME_COUNT();
    if (gtaVars->frameCount < newFrameCount) {
        gtaVars->frameCount = newFrameCount;

        Ped pedID = PLAYER_PED_ID();
        Player playerID = PLAYER_ID();

        /* define player coords */
        Vector3 playerCoords = GET_ENTITY_COORDS(pedID, 1);
        char waterRadius = 10;

        SET_SUPER_JUMP_THIS_FRAME(playerID);
        SET_PLAYER_INVINCIBLE(playerID, TRUE);

        if (IS_CONTROL_JUST_PRESSED(0, Button_Tpad)) {
            // teleport to beach
            SET_ENTITY_COORDS(pedID, -1374.881, -1398.835, 6.141, FALSE, FALSE, FALSE, TRUE);

            // set water
            MODIFY_WATER(playerCoords.x, playerCoords.y, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+2, playerCoords.y, waterRadius, 10);
            MODIFY_WATER(playerCoords.x, playerCoords.y+2, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+2, playerCoords.y+2, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+4, playerCoords.y, waterRadius, 10);
            MODIFY_WATER(playerCoords.x, playerCoords.y+4, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+4, playerCoords.y+4, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+6, playerCoords.y, waterRadius, 10);
            MODIFY_WATER(playerCoords.x, playerCoords.y+6, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+6, playerCoords.y+6, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+8, playerCoords.y, waterRadius, 10);
            MODIFY_WATER(playerCoords.x, playerCoords.y+8, waterRadius, 10);
            MODIFY_WATER(playerCoords.x+8, playerCoords.y+8, waterRadius, 10);
        }
    }

    return TRUE;
}

但是我从 GET_ENTITY_COORDS 收到多个错误即使我在脚本中定义了上面的函数，它仍然可以运行:

source/gta.c:42:3: error: unknown type name ‘Vector3’
   Vector3 playerCoords = GET_ENTITY_COORDS(pedID, 1);
   ^
source/gta.c:42:26: error: incompatible types when initializing type ‘int’ using type ‘struct Vector3’
   Vector3 playerCoords = GET_ENTITY_COORDS(pedID, 1);
                          ^
source/gta.c:53:29: error: request for member ‘x’ in something not a structure or union

有谁知道这个错误的原因是什么，以及如何修复它？我将非常感激，因为我已经为此苦苦挣扎了好几天，并且希望看到它得到解决，提前谢谢您。

Answer 1

如您的一些代码片段所示Vector3的用法如下:

static Inline struct Vector3 GET_ENTITY_COORDS

因此，既然这是有效的，这意味着它被定义为(在某些我们看不到的代码中)struct，而不是定义为 typedef struct(这将允许在没有 struct 关键字的情况下使用它)。

您的错误是在将变量声明为 Vector3 时出现的:

Vector3 playerCoords = GET_ENTITY_COORDS(pedID, 1);

应该是

struct Vector3 playerCoords = GET_ENTITY_COORDS(pedID, 1);

其余的错误只是该错误的结果。解析器此时丢失。