C结构初始化和分割故障

Question

我已经通过指针初始化了一个结构，我也尝试使用指针获得值。我正在分割错误。有任何线索吗？

#include <stdio.h>
#include <stdlib.h>

int main(void){
    struct MemData{
        char* FileName;
        int LastByteLength;
        int ReadPointer;
        int WritePointer;
        char Data[ 512000];//MEMORY BLOCK SIZE: 500 KB
    };
    struct MemData* M;
    M->FileName=(char*)"xaa";
    M->LastByteLength=0;
    M->ReadPointer=-1;
    M->WritePointer=-1;
    printf("n%s", M->FileName);
    printf("n%d", M->LastByteLength);
    printf("n%d", M->ReadPointer);
    printf("n%d", M->WritePointer);
}

Answer 1

您需要分配m。

#include <stdio.h>
#include <stdlib.h>

int main(void){
  struct MemData{
     char* FileName;
     int LastByteLength;
     int ReadPointer;
     int WritePointer;
     char Data[ 512000];//MEMORY BLOCK SIZE: 500 KB
  };
  struct MemData* M;
  M = malloc(sizeof(*M));
  M->FileName="xaa";
  M->LastByteLength=0;
  M->ReadPointer=-1;
  M->WritePointer=-1;
  printf("n%s", M->FileName);
  printf("n%d", M->LastByteLength);
  printf("n%d", M->ReadPointer);
  printf("n%d", M->WritePointer);
  free(M);
}

尝试上述代码，它应该有效。

正如Broman在评论中所建议的，我编辑了答案，以删除不必要的"(char*("字符串字面的铸件已经具有类型的char*