如何创建存储Contentor结构体的10×10矩阵并为元素创建线程

Let's walk through the key problems in your code that are breaking matrix storage and thread behavior, then fix them step by step:

Critical Issues in the Original Code #

• Mismatched Matrix Allocation: You can't assign a malloc result to a statically declared 2D array (struct Contentor parque[10][10]). Static arrays live on the stack, while malloc gives heap memory — pick one approach.
• Invalid String Assignment: Directly assigning string literals to char arrays with = "" won't work in C. Use strcpy or memset to initialize/modify struct character arrays properly.
• Wrong Thread Parameter: When creating threads, you're passing 1 instead of a pointer to the target Contentor struct. The thread function expects a Contentor*, so this causes undefined behavior.
• Backwards Empty Slot Check: strcmp(parque[i][j].nSerie,"") returns 0 when strings are equal (empty). Your condition checks for non-zero, meaning you're treating occupied slots as free and vice versa.
• Unseeded Random Numbers: rand() uses a fixed seed by default, so you'll get the same delay sequence every run. Use srand(time(NULL)) to seed it for true randomness.
• Sleep in the Wrong Place: Putting sleep(randomNumber) in the main thread pauses the entire loop, not individual worker threads. The delay should happen inside the thread function.
• Redundant Thread Attribute Setup: Reinitializing pthread_attr_t attr inside the nested loop is inefficient — initialize it once outside the loop.
• Invalid String Copy in Thread: char destino[4] = arg_struct->porto; is invalid syntax for copying char arrays. Use strcpy instead.

Fixed Code Implementation #

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <time.h>
#include <unistd.h>

struct Contentor {
    char nSerie[36];
    char porto[4];
};

void* direcionaParaDestino(void* arg) {
    struct Contentor *contentor = (struct Contentor*) arg;
    
    // Safely copy the porto value
    char destino[4];
    strcpy(destino, contentor->porto);
    
    // Generate random delay (0-4 seconds, max 5 total)
    int delay = rand() % 5;
    sleep(delay);
    
    // Process destination routing
    if(strcmp(destino, "ANR") == 0) {
        printf("Contentor %s routed to ANR after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "BUS") == 0) {
        printf("Contentor %s routed to BUS after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "DXB") == 0) {
        printf("Contentor %s routed to DXB after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "GUA") == 0) {
        printf("Contentor %s routed to GUA after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "HAM") == 0) {
        printf("Contentor %s routed to HAM after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "HKG") == 0) {
        printf("Contentor %s routed to HKG after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "LAX") == 0) {
        printf("Contentor %s routed to LAX after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "RTM") == 0) {
        printf("Contentor %s routed to RTM after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "SHA") == 0) {
        printf("Contentor %s routed to SHA after %d seconds\n", contentor->nSerie, delay);
    } else if (strcmp(destino, "SIN") == 0) {
        printf("Contentor %s routed to SIN after %d seconds\n", contentor->nSerie, delay);
    } else {
        printf("Contentor %s has unknown port %s\n", contentor->nSerie, destino);
    }
    
    pthread_exit(NULL);
}

int main() {
    // Seed random number generator for delays
    srand(time(NULL));
    
    // Static 10x10 matrix (stack-allocated, simpler for your use case)
    struct Contentor parque[10][10];
    
    // Initialize all slots to empty
    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 10; j++) {
            memset(parque[i][j].nSerie, 0, sizeof(parque[i][j].nSerie));
            memset(parque[i][j].porto, 0, sizeof(parque[i][j].porto));
        }
    }
    
    // Example: Populate some slots with test data
    strcpy(parque[0][0].nSerie, "SERIE001");
    strcpy(parque[0][0].porto, "LAX");
    
    strcpy(parque[2][3].nSerie, "SERIE002");
    strcpy(parque[2][3].porto, "HKG");
    
    strcpy(parque[5][5].nSerie, "SERIE003");
    strcpy(parque[5][5].porto, "SIN");
    
    pthread_t tids[10][10];
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    // Explicitly set thread to joinable (default, but clear)
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
    
    // Create threads only for occupied slots
    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 10; j++) {
            // Check if slot is occupied (nSerie is not empty)
            if(strcmp(parque[i][j].nSerie, "") != 0) {
                printf("Lugar [%d][%d] encontra-se Ocupado - creating thread\n", i, j);
                // Pass pointer to the specific Contentor struct
                int rc = pthread_create(&tids[i][j], &attr, direcionaParaDestino, &parque[i][j]);
                if(rc != 0) {
                    fprintf(stderr, "Failed to create thread for [%d][%d]\n", i, j);
                    exit(EXIT_FAILURE);
                }
            } else {
                printf("Lugar [%d][%d] encontra-se Livre\n", i, j);
            }
        }
    }
    
    // Clean up thread attributes
    pthread_attr_destroy(&attr);
    
    // Join only threads that were actually created
    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 10; j++) {
            if(strcmp(parque[i][j].nSerie, "") != 0) {
                pthread_join(tids[i][j], NULL);
            }
        }
    }
    
    printf("All threads completed processing\n");
    return EXIT_SUCCESS;
}

Key Improvements Explained #

1. Matrix Initialization: We use a static 10x10 array and initialize all char arrays with memset to ensure they start empty.
2. Proper String Handling: All string assignments use strcpy, the correct method for copying into char arrays in C.
3. Correct Thread Parameters: We pass a pointer to the specific Contentor struct when creating threads, so the thread function can access its data safely.
4. Independent Thread Delays: The random delay is moved inside the thread function, so each thread waits on its own without blocking the main loop.
5. Fixed Slot Check: We now correctly identify occupied slots with strcmp(parque[i][j].nSerie, "") != 0.
6. Clean Attribute Management: Thread attributes are initialized once and destroyed after use for proper resource cleanup.
7. Basic Error Checking: Added checks for pthread_create failures to catch issues early.

内容的提问来源于stack exchange，提问作者MyNameJeff