c - malloc.c 中的断言 :2453

Question

我有以下程序试图标记一个字符串(基于空格)并将其写入 char ** 数组。

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

#define len 180

void tokenize(char *str, char **tokens)
{
    int l = 0, index = 0;
    int i = 0;
    int str_i;
    int tok_i;

    while(*str) {
        if (*str == ' ') {
            tokens[i] = malloc(sizeof(char) * l+1);
            if (tokens[i] == NULL) return;

            tok_i = 0;           
            for (str_i=index-len ; str_i<index ; str_i++) {
                tokens[i][tok_i] = str[str_i];
                tok_i++;
            }

            tokens[i][tok_i] = '\0';
            tokens[i++] = NULL;
            l = 0;
            index++;
        }
        str++;
        l++;
        index++;
    }       

    return;         
}

int main()
{
    char str[len] = "this is a test string";
    char **tokens = malloc(100 * sizeof(char *));

    if (str == NULL || tokens == NULL)
        return 1;

    printf("input string: %s\n", str);
    tokenize(str, tokens);

    return 0;
}

上面的程序编译的很好，但是在执行的时候，我在malloc.c

中得到了下面的断言

$ gcc -ggdb -Wall prog.c 
$ ./a.out 
input string: this is a test string
a.out: malloc.c:2453: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed.
Aborted (core dumped)
$ 

堆栈跟踪显示如下:

(gdb) bt
#0  0x0000003b28036285 in raise () from /lib64/libc.so.6
#1  0x0000003b28037b9b in abort () from /lib64/libc.so.6
#2  0x0000003b2807d37d in __malloc_assert () from /lib64/libc.so.6
#3  0x0000003b28080c37 in _int_malloc () from /lib64/libc.so.6
#4  0x0000003b28082595 in malloc () from /lib64/libc.so.6
#5  0x000000000040055f in tokenize (str=0x7fffffffe017 " a test string", tokens=0x601010) at prog.c:15
#6  0x00000000004006de in main () at prog.c:46
(gdb) 

我该如何调试它？任何想法将不胜感激。

Answer 1

在你的 for 循环中

for (str_i=index-len ; str_i<index ; str_i++)

str_i 是一个负数。