Question

请在我的程序中调用以下函数，以帮助我解决SIGSEGV错误：

int* calculateFitness(int** population, int** townDistancesMatrix, int chromoSize){
    int sum = 0;
    static int* Fitnesses;
    Fitnesses = malloc(sizeof(int)*chromoSize); 
    for(int i=0; i<chromoSize; i++){
        int indexOne = 0;
        int indexTwo = 0;
        for(int j=0; j<chromoSize-1; j++){
            indexOne = population[i][j];
            indexTwo = population[i][j+1];
            //printf("\n%d %d",indexOne-1,indexTwo-1);
            sum += townDistancesMatrix[indexOne-1][indexTwo-1];
        }
        indexOne = population[i][0];
        sum += townDistancesMatrix[indexTwo-1][indexOne-1];
        Fitnesses[i] = sum;
        sum = 0;
    }
    return Fitnesses;
}

对于较小的输入（例如5个镇），程序运行没有问题，所以我首先怀疑它是stackoverflow的原因，因为程序始终运行一段时间（直到所有运行的i的值都相似（i=20），然后停止运行并给出此错误（在GDB中）：

程序收到信号SIGSEGV，分段错误。 0x0000000008000b9b在Untitled1.c：97的calculateFitness（人口= 0x7ffffffedcd0，townDistancesMatrix = 0x8403470，chromoSize = 48）中 97 sum + = townDistancesMatrix [indexOne-1] [indexTwo-1];

但是，我在calculateFitness中没有递归函数调用，因此我认为这可能是由于函数中的局部变量较大，但是局部变量又很小又很小，而且我的数组也是动态创建的，所以不要继续使用堆栈（也许问题出在我的嵌套循环上？）。

我还运行了valgrind（尽管我对它的报告还不太熟悉，我只是用它来获取一些提示），这是报告：

==198== error calling PR_SET_PTRACER, vgdb might block
==198== Use of uninitialised value of size 8
==198==    at 0x108B41: calculateFitness (Untitled1.c:92)
==198==    by 0x108866: main (Untitled1.c:29)
==198==
==198== Use of uninitialised value of size 8
==198==    at 0x108B6E: calculateFitness (Untitled1.c:93)
==198==    by 0x108866: main (Untitled1.c:29)
==198==
==198== Invalid read of size 4
==198==    at 0x108B9B: calculateFitness (Untitled1.c:97)
==198==    by 0x108866: main (Untitled1.c:29)
==198==  Address 0x522d43c is 4 bytes before a block of size 192 alloc'd
==198==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck- 
amd64-linux.so)
==198==    by 0x108A56: readDistances (Untitled1.c:74)
==198==    by 0x1087EB: main (Untitled1.c:19)
==198==
==198== Invalid read of size 8
==198==    at 0x108B87: calculateFitness (Untitled1.c:97)
==198==    by 0x108866: main (Untitled1.c:29)
==198==  Address 0x522d278 is 8 bytes before a block of size 384 alloc'd
==198==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck- 
amd64-linux.so)
==198==    by 0x108A20: readDistances (Untitled1.c:71)
==198==    by 0x1087EB: main (Untitled1.c:19)
==198==
==198==
==198== Process terminating with default action of signal 11 (SIGSEGV)
==198==  Access not within mapped region at address 0xFFFFFFFFFC000018
==198==    at 0x108B9B: calculateFitness (Untitled1.c:97)
==198==    by 0x108866: main (Untitled1.c:29)
==198==  If you believe this happened as a result of a stack
==198==  overflow in your program's main thread (unlikely but
==198==  possible), you can try to increase the size of the
==198==  main thread stack using the --main-stacksize= flag.
==198==  The main thread stack size used in this run was 8388608.

//...

==198== LEAK SUMMARY:
==198==    definitely lost: 0 bytes in 0 blocks
==198==    indirectly lost: 0 bytes in 0 blocks
==198==      possibly lost: 0 bytes in 0 blocks
==198==    still reachable: 13,632 bytes in 70 blocks
==198==         suppressed: 0 bytes in 0 blocks

我搜索了该错误的某些部分，例如“仍然可以到达”，这似乎不是我需要注意的地方，但是即使搜索了第一部分，我也不确定。我究竟做错了什么？如果确实是stackoverflow，那么除了递归之外，还有其他导致stackoverflow的原因吗？

Answer 1

int main(){
  int* population[POPSIZE];

和

for(int i=0; i<chromoSize; i++){
    int indexOne = 0;
    int indexTwo = 0;
    for(int j=0; j<chromoSize-1; j++){
        indexOne = population[i][j];
        indexTwo = population[i][j+1];

您访问的是人口（由 valgrind 表示），您为chromo_size（初始化上面的 chromoSize ）赋予的值48 ）中的 POPSIZE 等于20

在 indexOne 和 indexTwo 具有随机值之后，对 townDistancesMatrix 的访问会产生由valgrind发出信号的seg故障

在scanf("%d",&chromo_size);后的 main 中，检查值为<= POPSIZE 以避免该问题，并增加 POPSIZE 为能够与您的输入文件一起运行

还请注意free(population)是非法的，因为人口是局部变量，未在堆中分配

是什么导致此程序中的分段错误？

1 个答案: