Realloc问题

Question

感谢您的查找，请忽略-各种恶作剧正在发生，我正在尝试调试更多。

=====================================

有人能解释一下房地产的这种行为吗？

输出：

before realloc start: testing%20encryp
before realloc app: '          '
realloc size: 27
after realloc: testing%20e
strlen(newstr): 11
newstr: testing%20e

代码：

char * strAppend(char * start, char * app)
{
  int i=strlen(start);
  int j=0;
  printf("before realloc start: %s\n", start);
  printf("before realloc app: '%s'\n", app);
  printf("realloc size: %i\n", i+strlen(app)+1);
  char * newstr = realloc(start, sizeof(char) * (i + strlen(app) + 1));
  printf("after realloc: %s\n", newstr);
  while(app[j] != '\0')
    newstr[i++] = app[j++];
  printf("strlen(newstr): %i\n", strlen(newstr));
  printf("newstr: %s\n", newstr);
  return newstr; }

它从房地产交易开始就删除了"ncryp“，但这不应该发生.

编辑:更多代码，更多输出

char * urlEncode(char * c)
{
#ifdef EBUG
  printf("urlEncode: Encoding '%s'\n", c);
#endif
  int len = strlen(c)+1;
  char * ret = malloc(sizeof(char) * len);
  memset(ret, 0, len);
  int z=0;
  char * escapee = malloc(sizeof(char) * 4);
  escapee[0] = '%'; escapee[3] = '\0';
  for(int i=0;i<strlen(c);i++)
    {
      printf("z = %i len = %i ret = %s\n", z, len, ret);
      if(z >= len)
        {
          ret = strAppend(ret, "          ");
          len += strlen("          ");
        }
      printf("z = %i len = %i ret = %s\n", z, len, ret);
      if ( (48 <= c[i] && c[i] <= 57) ||//0-9
           (65 <= c[i] && c[i] <= 90) ||//abc...xyz
           (97 <= c[i] && c[i] <= 122) || //ABC...XYZ
           (c[i]=='~' || c[i]=='!' || c[i]=='*' || c[i]=='(' || c[i]==')' || c[i]=='\'')
           )
        {
          ret[z++] = c[i];
        }
      else
        {
          char2hex(c[i], escapee);
          ret = strAppend(ret, escapee);
          z += 3;
        }
    }
  ret[z] = '\0';
  free(escapee);
#ifdef EBUG
  printf("urlEncode: Encoded string to '%s'\n", c);
#endif
  return ret;
}




urlEncode: Encoding 'testing encrypt'
z = 0 len = 16 ret =
z = 0 len = 16 ret =
z = 1 len = 16 ret = t
z = 1 len = 16 ret = t
z = 2 len = 16 ret = te
z = 2 len = 16 ret = te
z = 3 len = 16 ret = tes
z = 3 len = 16 ret = tes
z = 4 len = 16 ret = test
z = 4 len = 16 ret = test
z = 5 len = 16 ret = testi
z = 5 len = 16 ret = testi
z = 6 len = 16 ret = testin
z = 6 len = 16 ret = testin
z = 7 len = 16 ret = testing
z = 7 len = 16 ret = testing
before realloc start: testing
before realloc app: '%20'
realloc size: 11
after realloc: testing
strlen(newstr): 10
newstr: testing%20
z = 10 len = 16 ret = testing%20
z = 10 len = 16 ret = testing%20
z = 11 len = 16 ret = testing%20e
z = 11 len = 16 ret = testing%20e
z = 12 len = 16 ret = testing%20en
z = 12 len = 16 ret = testing%20en
z = 13 len = 16 ret = testing%20enc
z = 13 len = 16 ret = testing%20enc
z = 14 len = 16 ret = testing%20encr
z = 14 len = 16 ret = testing%20encr
z = 15 len = 16 ret = testing%20encry
z = 15 len = 16 ret = testing%20encry
z = 16 len = 16 ret = testing%20encryp
before realloc start: testing%20encryp
before realloc app: '          '
realloc size: 27
after realloc: testing%20encryp
strlen(newstr): 26
newstr: testing%20encryp
z = 16 len = 26 ret = testing%20encryp

最后编辑：

我不知道现在发生了什么事。有和不带调试标志的程序的不同运行会产生不同的输出。我将返回到绘图板，并寻找内存错误使用瓦兰。

Answer 1

realloc的第一个参数必须是以前由malloc、calloc或realloc返回的指针，而不是随后的freed。

如果不是这样的话，任何事情都可能发生，包括你所看到的。

start从哪里来？

编辑：发布您的编辑，您似乎没有一个真正的问题！

Answer 2

我认为您要做的是将两个字符串启动& app连接起来，如果是这样的话，最好使用strncat函数。

#include <cstring>
char *strncat( char *str1, const char *str2, size_t count );

Answer 3

由于您原来的realloc问题似乎没有可重现性，我将敢于发布一个稍加重构的代码来完成您正在寻找的任务。它对字符串进行了两次传递，但我认为，在执行内存分配调用的次数方面，它应该具有更可预测的性能--只执行一次。它也比你的短一点。

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

int is_printable(char c) {
 return (48 <= c && c <= 57) ||//0-9
        (65 <= c && c <= 90) ||//abc...xyz
        (97 <= c && c <= 122) || //ABC...XYZ
        c == '~' || c =='!' || c== '*' ||
        c == '(' || c== ')' || c== '\'';
}

char *urlEncode(char *s) {
  char *ret, *c, *ct;
  int i, len;
  printf("urlEncode: Encoding '%s'\n", s);
  /* First pass - figure out how long the target string should be */
  len = 0;
  for(c=s; *c; c++) {
    if(is_printable(*c)) len++; else len += 3;
  }
  /* Don't forget we need to store terminating zero too */
  len++;
  printf("Current len: %d, target len: %d\n", strlen(s)+1, len);
  ct = ret = malloc(len);
  /* Second pass - copy/encode */
  for(c=s; *c; c++) {
    if(is_printable(*c)) {
      *ct++ = *c;
    } else {
      snprintf(ct, 4, "%%%02x", *c);
      ct += 3;
    }
  }
  *ct = 0; /* null-terminate the string */
  printf("Encoded string: %s\n", ret);
  return ret;
}

int main(int argc, char *argv[])
{
  urlEncode("testing encrypt");
  exit(1);
}