c++ - 尝试访问超出范围的数组时出现段错误，原因不明

Question

我正在做一个学校项目(我被允许用 C++ 为我的 Science Fair 项目进行模拟)，直到现在一切都很顺利(除了另一个我有问题的错误)。为了完全理解我在做什么，我建议你快速浏览一下 this page.

好的。下面是我的代码。当您尝试运行它时，您可以清楚地看到某些机器人的 x 和 y 坐标为负数，这是不应该发生的。我已经对所有操作进行了三重检查，对我来说一切都很好。我用了this帮助我理解数组中的 X 和 Y 相对位置。我的错误有什么明显的问题吗？我仍然习惯于多维数组，所以请考虑到这一点。另外，我知道其中大部分效率很低；清理它本身就是一个项目。谢谢，节日快乐!

*我的问题来自靠近底部的 moveBot 函数。让您阅读不必要的部分似乎是不对的。

更新代码:

// NANORG SIMULATION
// CREATED BY JACOB HARTMANN FOR THE SCIENCE FAIR (2013)
// CODED IN C++

#include <iostream>
#include <string>
#include <stdlib.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <cstdlib>

#include "bot.h"

using namespace std;

signed int map [40][70]; //2D array  x first, then y
int mapBot [40][70]; //If bot is there, 1. If not, 0   This array keeps track if there is a bot in a location
signed int currentTick = 0; //Signed just in case something goes wrong and goes into the -s
int maxTick = 1000000; //Should always stay at 1mil
signed int totalEnergy = 0;  //For some reason, when I add this here, everything breaks.

Bot bots[50];

void setupMap();
void tick();
void updateTickOutput();
void outputMapValue(int x, int y);
void assignBotID();
void setupBot();
void moveBot();
void manualMoveBot(int botID);
void mutateBot(int botID, int level, int sT);
void ckLoc(int botIdent);
void reassignLoc(int botID);
void gatherEnergy(int botID);

int main() {
    cout << "     ----------------------" << endl;
    cout << "     NANORG Simulation V1.3.1" << endl;
    cout << "Created in C++ by Jacob Hartmann" << endl;
    cout << "     ----------------------" << endl << endl;
        srand (time(NULL));
    cout << "Setting up map.. (Step 1)" <<endl;
    setupMap();
    cout << "Assigning botIDs.. (Step 2)" << endl;
    assignBotID();
    cout << "Setting up bots.. (Step 3)" << endl;
    setupBot();
    cout << "Starting ticks.. (Step 4)" << endl;
    tick();
//  outputMapValue(5,5);
//  mutateBot(5, 2); //Just to test
/*  cout << endl << "X before: " << bots[5].x_cord << " Y before: " << bots[5].y_cord << endl;
    moveBot(5);
        cout << "X after: " << bots[5].x_cord << " Y after: " << bots[5].y_cord << endl;
    cout << "Energy before: " <<  bots[5].energy <<endl;
    gatherEnergy(5);
    cout << "Energy after: " << bots[5].energy << endl; */ //DEBUG
    return 0;
}

void setupMap(){
//  srand (time(NULL)); //Not a good idea to put it here
    for(int i = 0; i < 40; i++){
        for(int j = 0; j < 70; j++){ // We add one extra (70) so it fills the entire array. Same for above
            map[i][j] = rand() % 2 + 1; // 1==normal 2==toxic
        }
    }
//  outputMapValue(5,4); //Debugging purposes
//  outputMapValue(7,9);
    cout << "Map setup - \033[0;32mSuccessful" << "\033[0m" << endl;
}

void outputMapValue(int x, int y){
    cout << "The chunk value at (" << x+1 << ", " << y+1 << ") is: ";
    cout << map[x][y]; //Outputting the value of (x,y)
    if(map[x][y]==1){ //If (x,y) is == 1, the chunk is fine to eat
        cout << "  |  Chunk is not toxic." << endl;
    }
    if(map[x][y]==2){
        cout << "  |  Chunk is toxic." << endl;
    }
}

void updateTickOutput() {
        //cout << "Map Size (x,y): " << " " <<  mapsizeX << "," << mapsizeY << endl;      This function used to just refresh everything, including map size, which really isn't needed.         cout << "Current Tick: " << currentTick << " " << "Max Tick: " << maxTick << endl; //Just outputting currentTick and maxTick
    cout << "Score: " << totalEnergy << endl;
}

void tick() {
        while(true){
                if(currentTick <= maxTick){
                        currentTick += 1;
            moveBot();
/*          if(currentTick >= 900000){ //If currentTick is over 900,000: we will begin to output individual ticks. Anything less and we get a seg fault.
                updateTickOutput(); //See above
            }*/
//          cout << "tick!";       This was for debugging, before I made the updateTickOutput() function to make sure that the program actually ticked
        }
            else if(currentTick == maxTick){
                        cout << endl << "Done!" << endl; //Report that we are finished with the simulation.
//          assignBotID(); //Make sure every bot has the proper ID. Moved to main()
                        break; //Kill the loop
                }
//                updateTickOutput(); //No real need for this, anymore.
        }
}


void setupBot(){
    srand(time(NULL));
    for(int botNumber=0;botNumber <= 50; botNumber++){
//          cout << "debug (botNumber): " << botNumber << endl;  //Debug feature
            bots[botNumber].x_cord = rand() % 39 + 1;
//          cout << "debug (bot x cord): " << bots[botNumber].x_cord << endl;  //Debug feature
            int bufferX = bots[botNumber].x_cord;
            bots[botNumber].y_cord = rand() % 69 + 1;
//          cout << "debug (bot y cord): " << bots[botNumber].y_cord << endl;  //Debug feature
            int bufferY = bots[botNumber].y_cord;
            if(mapBot[bufferX][bufferY] == 1){
                cout << endl <<"A bot already is here!" << endl;
                reassignLoc(botNumber);
            }
            else{
                mapBot[bufferX][bufferY] = 1; //Take the bot's cords and make sure everyone knows that a bot is there.
//              cout<< "debug (map location):"<<mapBot[bufferX][bufferY] << endl ;   Just a nice debug feature
            }
        //  if(botNumber==5){
        //      cout << "bot 5 assigned";    //I broke this entire function a while back and I used this to test if I was assigning bots correctly.
        //  }
    }

/*  cout << endl << "X: " << bots[5].x_cord+1 << endl;   //Just some debugging stuff below
    cout << "Y: " << bots[5].y_cord+1 << endl;
   //   cout << "The value at " << mapBot[bots[5].x_cord]<<","<< mapBot[bots[5].y_cord]<<" is: "  << mapBot[bots[5].x_cord][bots[5].y_cord];   //This is a very messed up debug feature, but it still works.

        cout << endl << "X: " << bots[6].x_cord+1 << endl;
        cout << "Y: " << bots[6].y_cord+1 << endl;
    cout << mapBot[6][6];
*/
    cout << "Bot setup - \033[0;32mSuccessful" << "\033[0m" << endl;
}

void assignBotID(){
    for(int i = 0; i < 50; ++i){
        bots[i].id = i + 1;
    }

/*  int botNumber = 0;
    string botName = "Bot";
    string finalName;

    string buffer;

    while(botNumber <50){
        if(botNumber < 50){
            botNumber = botNumber + 1;
            buffer = to_string(botNumber);
            finalName = botName + buffer;
            //finalName.id = botNumber;  A very very broken line.
            bots[botNumber].id = botNumber;
//          cout << finalName << ":"<< bots[botNumber].id << endl;  A super awesome debugging output to make sure the bot's id is correct
        }
        else if((botNumber = 51)){ //Redundancy :)
            break;
        }
    }*/
}

void mutateBot(int botID, int level, int sT){
    if((sT=2)){
        bots[botID].mutationLevel = bots[botID].mutationLevel + level;
    }
    else if((sT=1)){
        bots[botID].mutationLevel = bots[botID].mutationLevel - level;
    }
//  cout << botID << ":" << bots[botID].mutationLevel << endl; //Just a quick debugging feature to make sure it worked
}

void ckLoc(int botIdent){
    int bufferX;
    int bufferY;
    bufferX = bots[botIdent].x_cord;  //Just set the buffers. Uses a bit more memory, but that is okay.
    bufferY = bots[botIdent].y_cord;
//  cout << bufferX << endl << bufferY;
    if(mapBot[bufferX][bufferY] ==1){
        cout << "Bot lives here!";
        reassignLoc(botIdent);
    }
}

void reassignLoc(int botID){
    bots[botID].x_cord = rand() % 39 + 1;
    bots[botID].y_cord = rand() % 69 + 1;
    ckLoc(botID);
}

void moveBot(){
    for(int botID=1;botID<=50;botID++){
        int direction = 0;
    //  int bufX = bots[botID].x_cord;
    //  int bufY = bots[botID].y_cord;
        direction = rand() % 4 + 1;
        if(direction == 1){ //NORTH
            if(bots[botID].y_cord==0 || mapBot[bots[botID].x_cord][bots[botID].y_cord=-1] == 1){
                //cout << "error moving bot - N ";
                manualMoveBot(botID);
            }
            else{
                //cout << "BufferY: " << bufferY;
                bots[botID].y_cord -= 1;
                    gatherEnergy(botID);
            }
        }
        else if(direction == 2){ //EAST
            if(bots[botID].x_cord == 39 || mapBot[bots[botID].x_cord+=1][bots[botID].y_cord] == 1){
                //cout << "error moving bot - E";
                manualMoveBot(botID);
            }
            else{
                bots[botID].x_cord += 1;
                    gatherEnergy(botID);
            }
        }
            else if(direction == 3){ //SOUTH
                    if(bots[botID].y_cord  == 69 || mapBot[bots[botID].x_cord][bots[botID].y_cord+=1] == 1){
                             //cout << "error moving bot - S ";
                            manualMoveBot(botID);
                    }
                    else{
                            bots[botID].y_cord += 1;
                    gatherEnergy(botID);
                    }
            }
            else if(direction == 4){ //WEST
                    if(bots[botID].x_cord  == 0 or mapBot[bots[botID].x_cord=-1][bots[botID].y_cord] == 1){
                            //cout << "error moving bot - W";
                            manualMoveBot(botID);
                    }
                    else{
                            bots[botID].x_cord -= 1;
                    gatherEnergy(botID);
                    }
            }
//  gatherEnergy(botID); //Moved this to indivdual (spelling) stuff above. Just in case :)
//  cout << endl << "Direction: " << direction << endl; //Debug
    }
}

void manualMoveBot(int botID){
                int direction = 0;
 //               int bufX = bots[botID].x_cord;
//                int bufY = bots[botID].y_cord;
                direction = rand() % 4 + 1;
                if(direction == 1){ //NORTH
                        if(bots[botID].y_cord==0 || mapBot[bots[botID].x_cord][bots[botID].y_cord-1] == 1){
                                //cout << "error moving bot - N ";
                                manualMoveBot(botID);
                        }
                        else{
                                //cout << "BufferY: " << bufferY;
                                bots[botID].y_cord -= 1;
                               gatherEnergy(botID);
                        }
                }
                else if(direction == 2){ //EAST
                        if(bots[botID].x_cord == 39 || mapBot[bots[botID].x_cord+1][bots[botID].y_cord] == 1){
                                //cout << "error moving bot - E";
                                manualMoveBot(botID);
                        }
                        else{
                                bots[botID].x_cord += 1;
                               gatherEnergy(botID);
                        }
                }
                else if(direction == 3){ //SOUTH
                        if(bots[botID].y_cord  == 69 || mapBot[bots[botID].x_cord][bots[botID].y_cord+1] == 1){
                                 //cout << "error moving bot - S ";
                                manualMoveBot(botID);
                        }
                        else{
                                bots[botID].y_cord -= 1;
                                gatherEnergy(botID);
                        }
                }
                else if(direction == 4){ //WEST
                        if(bots[botID].x_cord  == 0 or mapBot[bots[botID].x_cord-1][bots[botID].y_cord] == 1){
                                //cout << "error moving bot - W";
                                manualMoveBot(botID);
                        }
                        else{
                                bots[botID].x_cord += 1;
                                gatherEnergy(botID);
        }
    }
}

void gatherEnergy(int botID){
//  int mV = map[bufferX][bufferY];  //Eeeeh, doesn't work here
    int x = bots[botID].x_cord;
    int y = bots[botID].y_cord;
//  cout << "id: " << botID << endl;
//  cout << "x: " << x;
//  cout << endl << "y: " << y << endl;
    if(1==map[x][y]){  //Good chunk
        bots[botID].energy += 2000;
        totalEnergy += 2000;
    //  cout << totalEnergy << endl; //Debug
    }
    else if(2==map[x][y]){ //Bad chunk (toxic)
        mutateBot(botID, 1, 2);
    }
}

Answer 1

你有几个问题。

最主要的是数组的索引:
所以对于 Bot bots[50]; 有效索引是 [0; 49].
对于 map，根据竞赛，它应该是 int mapBot [40][70];
因此您可以访问从 mapBot[0][0] 到 mapBot[39][69] 的元素。

你在一些比较中混淆了 = 和 ==。
当 == 进行比较时，= 进行赋值。我看到您添加了额外的括号以删除警告。您必须更仔细地阅读/理解警告信息。例如，else if((currentTick = maxTick)){ in tick 应该是 else if (currentTick == maxTick) {.< br/>同样在 mutateBot...

在 AssigningBotID 中，您在访问数组之前递增索引并进行冗余检查。以下就足够了:

void assignBotID() {
    for (int i = 0; i < 50; ++i) {
        bots[i].id = i /* + 1 */; // uncomment if id should be [1; 50]

        // A super awesome debugging output to make sure the bot's id is correct
        //std::cout << "Bot" << i << ":"<< bots[i].id << endl;
    }
}

在 manualMoveBot 中，您的测试可能会改变位置，因为您使用了 +=:mapBot[bots[botID].x_cord += 1][bots[botID].y_cord] == 1应该是 mapBot[bots[botID].x_cord + 1][bots[botID].y_cord] == 1

您的逻辑忘记更新mapBot:旧位置应设置为0，新位置应设置为 1。请注意，在初始化期间，它并不总是设置...

编辑:您应该只调用 srand (time(NULL)); 一次(main() 中的那个)

setupBot() 应该是这样的(因此 reassignLoc 和 ckLoc 可能会被删除):

void setupBot() {
    for (int i = 0; i < 50; ++i) {
        int x, y;
        do {
            x = rand() % 40; // [0; 39]
            y = rand() % 70; // [0; 69]
        while (mapBot[x][y] == 1);

        bots[i].x_cord = x;
        bots[i].y_cord = y;
        mapBot[x][y] = 1;
    }
    cout << "Bot setup - \033[0;32mSuccessful" << "\033[0m" << endl;
}

mutateBot 尚未修复:将 = 替换为 == 进行比较。

void moveBot() {
    for (int i = 0; i < 50; ++i) {
        manualMoveBot(botID);
    }
}

void manualMoveBot(int botID) {
    const int oldX = bots[botID].x_cord;
    const int oldY = bots[botID].y_cord;
    int newX = oldX;
    int newY = oldY;
    int direction = rand() % 4 + 1;

    if (direction == 1) { // NORTH
        newY = oldY - 1;
    } else if (direction == 2) { // EAST
        newX = oldX + 1;
    } else if (direction == 3) { // SOUTH
        newY = oldY + 1;
    } else if (direction == 4) { // WEST
        newX = oldX - 1;
    }

    if (newX < 0 || 40 <= newX
        || newY < 0 || 70 <= newY
        || mapBot[newX][newY] == 1) {
        cout << "error moving bot";
#if 0
        // if this code is active, we may have infinite loop
        // when bot is completely surrounded.
        manualMoveBot(int botID);
#endif
        return;
    }
    bots[botID].x_cord = newX;
    bots[botID].y_cord = newY;
    mapBot[newX][newY] = 1;
    mapBot[oldX][oldY] = 0;
    gatherEnergy(botID);
}