free()：下一个大小无效（正常）& munmap_chunk()：C 中的指针无效

Question

一次又一次调用函数 enc() 和 dec()，它抛出错误，但创建了新的加密文件。

如果先调用enc()再使用加密文件，如果在dec()中使用则显示错误：munmap_chunk(): invalid pointer

如果调用 enc() 并且您终止程序，稍后运行它并在现在加密的文件上使用 dec()，它显示 错误：免费（ ): 下一个尺寸无效（正常）

void enc()
{
    FILE *fp1, *fp2;
  char filename1[FILENAME_MAX];
  int i;
  int size;
  int shift;


  printf("Enter filename:");
  scanf(" %[^\n]s",filename1);

  while((fp1 = fopen(filename1, "r")) == NULL){
    fprintf(stderr, "Error: Unable to open file %s\nTry Again\n", filename1);
    printf("Enter filename:");
    scanf(" %[^\n]s",filename1);
  }


  printf("Enter shift:");
  scanf("%d",&shift);

  const char *prefix = "encrypted_";
  char *filename2;
  filename2 = (char *)malloc(sizeof(strlen(filename1) + strlen(prefix)+1)); 
  strcpy(filename2, prefix);
  strcat(filename2, filename1);
  if ((fp2 = fopen(filename2, "w")) == NULL) {
    fprintf(stderr, "Error: Unable to open file %s\n", filename1);
    exit(EXIT_FAILURE);
  }
  free(filename2);



  int ch;
  while ((ch = getc(fp1)) != EOF) {
    if (ch >= 'A' && ch <= 'Z') {
      putc(((ch - 'A') + shift) % 26 + 'A', fp2);
    } 
    else if (ch >= 'a' && ch <= 'z') {
      putc(((ch - 'a') + shift) % 26 + 'a', fp2);
    } 
    else {
      putc(ch, fp2);
    }
  }
  fclose(fp1);
  fclose(fp2);
}

void dec()
{
    FILE *fp1, *fp2;
  char filename1[FILENAME_MAX];
  int i;
  int size;
  int shift;


  printf("Enter filename:");
  scanf(" %[^\n]s",filename1);


  while((fp1 = fopen(filename1, "r")) == NULL){
    fprintf(stderr, "Error: Unable to open file %s\nTry Again\n", filename1);
    printf("Enter filename:");
    scanf(" %[^\n]s",filename1);
  }

  printf("Enter shift:");
  scanf("%d",&shift);
  shift = 26-(shift%26);

  const char *prefix = "decrypted_";
  char *filename2;
  filename2 = (char *)malloc(sizeof(strlen(filename1) + strlen(prefix)+1)); 
  strcpy(filename2, prefix);
  strcat(filename2, filename1);
  if ((fp2 = fopen(filename2, "w")) == NULL) {
    fprintf(stderr, "Error: Unable to open file %s\n", filename1);
    exit(EXIT_FAILURE);
  }
  free(filename2);



  int ch;
  while ((ch = getc(fp1)) != EOF) {
    if (ch >= 'A' && ch <= 'Z') {
      putc(((ch - 'A') + shift) % 26 + 'A', fp2);
    } 
    else if (ch >= 'a' && ch <= 'z') {
      putc(((ch - 'a') + shift) % 26 + 'a', fp2);
    } 
    else {
      putc(ch, fp2);
    }
  }
  fclose(fp1);
  fclose(fp2);
}

Answer 1

filename2 = (char *)malloc(sizeof(strlen(filename1) + strlen(prefix)+1));

您正在为 sizeof(size_t) 保留 space 并可能调用 malloc(8)，删除 sizeof 关键字：

filename2 = malloc(strlen(filename1) + strlen(prefix)+1);

free()：下一个大小无效（正常）& munmap_chunk()：C 中的指针无效

free(): invalid next size (normal) & munmap_chunk(): invalid pointer in C

c

c++

gdb

pointers

dynamic-memory-allocation