C ++线程中的分段错误

Question

我试图在C ++中建立一个基本的线程类，但是当我尝试创建线程时却遇到了段错误。 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：

线程.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

线程.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;
    }

对这里出什么问题有任何想法吗？

Answer 1

ThreadState *state;
state->mLimit = pLimit;

您正在写入尚未分配的内存

Answer 2

您在ThreadState中有一个未初始化的指针。 在第35行，您创建了一个指向ThreadState的指针，但从未分配该指针指向任何ThreadState对象。

记住，指针只是一个内存地址。 “ ThreadState *”仅表示“这是一个内存地址，我们可以将内存中的数据解释为我持有的作为ThreadState对象的地址。”

也许您打算执行“ ThreadState * state = new ThreadState（）;”？ 别忘了，有人在使用完该线程状态对象后将需要删除它，以免泄漏内存！