c - 在 C 中使用 free() 时出现问题

Question

我在使用免费版时遇到问题。我想分配一个 *chars 的二维数组并释放它们，但它在运行时失败。我正在学习指针，可能会让这个变得复杂化。

  //NUMBEROFLINES, NUMBEROFDIE, and WIDTHOFDIE are some ints (3, 2, 3),
  int iLineSize, iLine, iDie;
  char **piDieString;

  piDieString = (char**)malloc(NUMBEROFLINES * sizeof(*piDieString)); //Allocate number of lines
  iLineSize = NUMBEROFDIE * WIDTHOFDIE * sizeof(char); //Size of line
  for(iLine = 0; iLine < NUMBEROFLINES; iLine++)
  {
     piDieString[iLine] = (char*)malloc(iLineSize); //Allocate size of lines
  }

  //Stuff happens

  /*Freeing*/
  for(iLine = 0; iLine < NUMBEROFLINES; iLine++)
     {
     free(piDieString[iLine]);
     }
  free(piDieString);

Answer 1

我相信//Stuff comes有问题。

添加了打印以验证内存是否正确分配和释放，如下所示:

#include <stdio.h>
#define NUMBEROFLINES 3
#define NUMBEROFDIE 2
#define WIDTHOFDIE 3
int main(void) {

  int iLineSize, iLine, iDie;
  char **piDieString;

  piDieString = (char**)malloc(NUMBEROFLINES * sizeof(*piDieString)); //Allocate number of lines
  printf("Allocated piDieString: 0x%x\n",piDieString );
  iLineSize = NUMBEROFDIE * WIDTHOFDIE * sizeof(char); //Size of line

  for(iLine = 0; iLine < NUMBEROFLINES; iLine++)
  {
     piDieString[iLine] = (char*)malloc(iLineSize); //Allocate size of lines
     printf("Allocating piDieString[%d]: 0x%x\n",iLine,piDieString[iLine] );
  }

  //Stuff happens

  /*Freeing*/
  for(iLine = 0; iLine < NUMBEROFLINES; iLine++)
  {
     printf("Freeing piDieString[%d]: 0x%x\n",iLine,piDieString[iLine] );
     free(piDieString[iLine]);
  }

  printf("\nFreeing piDieString: 0x%x\n",piDieString );
  free(piDieString);
  return 0;
}

输出是这样的，看起来不错。

Allocated piDieString: 0x966e008
Allocating piDieString[0]: 0x966e018
Allocating piDieString[1]: 0x966e028
Allocating piDieString[2]: 0x966e038
Freeing piDieString[0]: 0x966e018
Freeing piDieString[1]: 0x966e028
Freeing piDieString[2]: 0x966e038

Freeing piDieString: 0x966e008

详细说明“但它在运行时失败”...您是否看到崩溃？如果是，请检查 //Stuffgenesis 是否存在无效的内存访问...