分离和退出线程的内存错误和泄漏？

Question

我创建了一个简单的程序，它使用线程解析日志文件并打印一个值。在阅读了creating detached threads 之后，我在我的主函数中使线程分离并销毁了属性（PTHREAD_CREATE_DETACHED）。我还退出了线程（不退出会造成更多的内存泄漏）。但是，我仍然有内存泄漏和错误，即使我很确定我不会在程序的其余部分中 malloc 任何东西。完整代码如下：

*感谢 Jonathan Leffler 解析分隔字符串的 strtok_fixed 函数

static char *strtok_fixed(char *str, char const *delims)
{
    static char  *src = NULL;
    char  *p,  *ret = 0;

    if (str != NULL)
        src = str;

    if (src == NULL || *src == '\0')    // Fix 1
        return NULL;

    ret = src;                          // Fix 2
    if ((p = strpbrk(src, delims)) != NULL)
    {
        *p  = 0;
        //ret = src;                    // Unnecessary
        src = ++p;
    }
    else
        src += strlen(src);

    return ret;
}

void * parse_log(void *arguments){

    file = fopen("oms_requests.log", "r");
    char c;

    if (file == NULL){                        //no valid file
        printf("couldn't find the file\n");
    } else {
        int f = fseek(file, -2, SEEK_END);
        if (f == 0){
            int counter = 1;
            c = fgetc(file);
            while (c != '\n'){
                counter++;
                fseek(file, -counter, SEEK_END);
                c = fgetc(file);
            }

            //now read last line in the log into buff 
            char buff[counter];
            int l = fread(buff, 1, counter, file);
            buff[counter-1] = '\0';

            if (l != counter-1){
                printf("counter is wrong\n");
            } else {
                //skip over 22 commas to get the value that I want 
                char *buffer = strtok_fixed(buff, ",");
                for (int i = 0; i < 22; i++){
                    buffer = strtok_fixed(NULL, ",");
                    if (buffer == '\0') i++;
                        printf("%s\n", buffer);
                    }
                    printf("%ld\n", strtol(buffer, NULL, 10));
                }
        } else {
            printf("error in getting to bottom of file\n");
        }
    }
    fclose(file);
}


int main(int argc, char *argv[])
{
    //create pthread attributes and set to detached 
    pthread_t thr;
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

    int l = pthread_create(&thr, &attr, parse_log, NULL);
    if (l != 0){
        printf("Didn't work\n");
        return -1;
    }

    //destroy pthread attribute and exit 
    pthread_attr_destroy(&attr);
    pthread_exit(&thr);
    return 0;
}

这是我运行程序时 valgrind 给出的报告：

==12387== HEAP SUMMARY:
==12387==     in use at exit: 272 bytes in 1 blocks
==12387==   total heap usage: 7 allocs, 6 frees, 2,510 bytes allocated
==12387==
==12387== Searching for pointers to 1 not-freed blocks
==12387== Checked 8,486,312 bytes
==12387==
==12387== 272 bytes in 1 blocks are possibly lost in loss record 1 of 1
==12387==    at 0x4C2CC70: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==12387==    by 0x4012E54: _dl_allocate_tls (dl-tls.c:296)
==12387==    by 0x4E3FDA0: pthread_create@@GLIBC_2.2.5 (allocatestack.c:589)
==12387==    by 0x400E11: main (in /afs/.ir.stanford.edu/users/d/i/dianale/CS107/assign1a/reassemble)
==12387==
==12387== LEAK SUMMARY:
==12387==    definitely lost: 0 bytes in 0 blocks
==12387==    indirectly lost: 0 bytes in 0 blocks
==12387==      possibly lost: 272 bytes in 1 blocks
==12387==    still reachable: 0 bytes in 0 blocks
==12387==         suppressed: 0 bytes in 0 blocks
==12387==
==12387== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

我也尝试过 pthread_detach(&thr) 而不是设置属性（我也尝试过同时拥有两者），但我仍然遇到完全相同的内存泄漏和错误。有没有什么办法解决这一问题？

Answer 1

Pthreads 分配一定数量的内存来维护每个线程的内部状态。分离一个线程只标志着这些资源可以在线程退出后立即回收（而不是保持状态以防其他线程可能需要它）。 Butt 这些资源将保持分配状态，直到线程完成执行。 Valgrind 可能会将它们报告为可能的“泄漏”。

还请记住，valgrind 有时会报告误报。我也没有在您的代码中看到任何可能导致泄漏的明显内容。所以我不会担心那些“可能泄漏”的消息。