Linux上的C++分段錯誤

Question

對不起，我是C++和linux的新手，我以前沒見過分段錯誤。我可以成功編譯該文件，但它只是輸出分段錯誤。

我試圖谷歌分段錯誤，但仍然沒有線索如何解決我的代碼。

希望有人能救我並告訴我什麼是錯的通過具體說明我犯的錯誤。 我將不勝感激！非常感謝！

#include <iostream> 
#include <cstdlib> 
#include <pthread.h> 
#include <unistd.h> 
#include <time.h> 
#include <cstring> 
#include <semaphore.h> 

using namespace std; 

#define NUM_THREADS  36 
#define MAX 36 

char matrix[6][6]; //result sheet 

//queue elements 
char queue[MAX], head=0, tail=0; 


int row=0,col=0; 
int runtime=1; // track the number of times we have run the dispatch 
funciton 

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 

void dispatch(){ 

    row = runtime/6; 
    sleep(1); //wait 1 second to generate column number 
    col = runtime % 6 - 1; 
    if (runtime % 6 == 0) 
     col = 5; 

    runtime++; 

} 


void enqueue(char c){ 
    queue[tail] = c; 
    tail = (tail+1)%MAX ; 
} 

char dequeue(){ 
    char temp = queue[head]; 
    head = (head+1)%MAX ; 
return temp; 
} 




//master thread 
void *qcTask(void *args) { 
//simulate product convey delay 
    sleep(1); 

    pthread_mutex_lock(&mutex); 

    dispatch(); 

    sleep(rand()%6+5); 

    if(rand()%100<90) 
     enqueue('Q'); 

    else 
     enqueue('U'); 

    pthread_mutex_unlock(&mutex); 

    pthread_exit(NULL); 
} 



int main (int argc, char* argv[]){ 


    int input = atoi(argv[1]); 
    //error handling 
    if(argc!=2 || input < 0 || input>36){ 
     cout<<"Input is illegal!"; 
    } 

    else{ 
     pthread_t threads[input]; 


     int rc, i, count = 0; 

     srand(time(NULL)); 

    for(i = 0;i<input;i++){ 

     rc = pthread_create(&threads[i], NULL, qcTask, NULL); 
     if (rc){ 
      cout << "Error:unable to create thread," << rc << endl; 
      exit(-1); 

    } 
    } 

    for (i = 0; i < input; i++){ 
     rc = pthread_join(threads[i], NULL); 
     if (rc){ 
      cout << "Error:unable to join," << rc << endl; 
      exit(-1); 
     } 
      } 

    //initize matrix with default value 'i' 
    for (int i = 0; i < 6; i++){ 
     for (int j = 0; j < 6; j++){ 
      matrix[i][j] = 'I'; 
     } 
    } 

    //fill the result sheet 
    for(int i=0;i<6;i++){ 
     for (int j = 0; j < 6; j++){ 
      matrix[i][j]=dequeue(); 
     } 

    } 

    for (int i = 0; i < 6; i++){ 
     for (int j = 0; j < 6; j++){ 
      cout << matrix[i][j]; 
      if (matrix[i][j] == 'U') 
       count++; 
     } 
     cout << endl; 
    } 

    cout << count << " products are unqualified."; 
    pthread_exit(NULL); 

    } 
} 

Answer 1

分段故障（段錯誤/ SIGSEGV）簡單地意味着該OS檢測到你的程序嘗試分配給它的地址空間之外訪問存儲器。可能有很多的原因（幾乎總是由中的錯誤引起的代碼）。 實例包括：

• 訪問一個未初始化的指針

• 寫過去的數組的末尾（或其它容器）

• 解引用nullptr

• 寫入或讀free'd memory

還有更多..