Question

我正在尝试在C ++中设置一个基本的线程类，但是当我尝试创建一个线程时，我遇到了一个seg错误。以下是GDB报告的内容：

Program received signal SIGSEGV, Segmentation fault.
0x0000000000401b68 in StartThread (pFunction=
    0x401ad2 <FindPrimesThread(void*)>, pLimit=5000000) at Thread.cpp:35
35          state->mLimit = pLimit;

当我尝试这样称呼它时：

ThreadState *primesState = StartThread(FindPrimesThread, 5000000);

这是我的代码：

Thread.hpp

#ifndef THREAD_HPP
#define THREAD_HPP

#include <pthread.h>
#include "Types.hpp"

typedef struct {
    ulong       mLimit;     // Upper limit of numbers to test 
    int         mStarted;   // True if the thread started successfully
    int         mExitCode;  // Thread exit code
    pthread_t   mThreadId;  // Thread ID
} ThreadState;

// Defines a type named ThreadFunction which is a pointer to a function with void * as the parameter and
// void * as the return value.
typedef void *(*ThreadFunction)(void *);

ThreadState *StartThread
    (
    ThreadFunction const pFunction,  // Pointer to the thread function
    ulong const          pLimit      // Upper limit of numbers to test
    );

#endif

Thread.cpp

#include "Amicable.hpp"
#include "Keith.hpp"
#include "Main.hpp"
#include "Prime.hpp"
#include "Thread.hpp"

ThreadState *StartThread
    (
    ThreadFunction const pFunction,  // Pointer to the thread function
    ulong const          pLimit      // Upper limit of numbers to test
    ) {
        ThreadState *state;
        state->mLimit = pLimit;
        pthread_t threadId;
        state->mStarted = pthread_create(&threadId, NULL, pFunction, (void *)state);
        if(state->mStarted == 0){
            state->mThreadId = threadId;
        }
        return state;
    }

对这里出了什么问题有什么想法？

Answer 1

ThreadState *state;
state->mLimit = pLimit;

您正在写入尚未分配的内存

Answer 2

你在ThreadState中有一个未初始化的指针。在第35行，您创建一个指向ThreadState的指针，但您永远不会指定该指针指向任何ThreadState对象。

请记住，指针只是一个内存地址。 “ThreadState *”只是意味着“这是一个内存地址，我们可以将内存中的数据解释为我所持有的ThreadState对象。”

也许你打算做“ThreadState * state = new ThreadState（）;”？不要忘记，有人需要在使用它时删除该ThreadState对象，以免泄漏内存！

C ++线程中的分段错误

2 个答案: