realloc():下一个大小无效:后跟32位寄存器

Question

所以我一直在用C编写一个mtf编码器,无论我做什么,我都遇到了realloc()错误.我已经通过使用print语句查看我的逻辑中是否存在错误(可能存在错误),看看我是否超出了当前malloc'd数组的范围(添加了超出原始数组大小的字符串)这似乎不是问题.我使用过GDB和Valgrind,而GDB给我一个神秘的信息,而Valgrind遇到了一个分段错误.这是我第一次使用动态内存,我对这个问题很困惑,下面是我的代码以及GDB错误:

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

int count = 0;


move_to_front(int index, char** words){
    int i;
    char *t = words[index];

    for(i = index; i>1; i--){
       words[i] = words[i-1];
    }

    words[1] = t;

}


char** reallocate_words(char** words, int* words_size_pointer){
   printf("We're entering here\n");
   printf("%d", *words_size_pointer);
   int temp = *words_size_pointer;
   char** tempor;
   temp = temp*2;
   printf("%d", temp);
   tempor = (char**) realloc(words, temp);
   int i = *words_size_pointer;
   for(i; i<temp; i++){
       tempor[i] = (char*) malloc(120);
    }
   words_size_pointer = &temp;
   return tempor;

 }

void encode_word(int* words_size_pointer, FILE *f, char* word, char** words){
    if(count == 0){
        words[1] = word;
        fputs(words[1], f);
        count++;
    }
    int i;
    for(i=0; i<=count; i++){
        if(strcmp(words[i], word) == 0){
            break;
        }
    }
    if(i>=(*words_size_pointer)){
        printf("%d\n", i);
        words = reallocate_words(words, words_size_pointer);
        words[count+1] = word;
        count++;
        fputc(count+128, f);
        fputs(words[count], f);
        move_to_front(count, words);
    }
    if(i>count){
        words[count+1] = word;
        count++;
        fputc(count+128, f);
        fputs(words[count], f);
        move_to_front(count, words);
    }
    else{
        fputc(i+128, f);
        move_to_front(i, words);
    }



}

void sep_words(char** words, char *line, int* words_size_pointer, FILE *f){
    char* x;
    int i = 0;
    x = strtok(line, " ");
    while(x != NULL){
        encode_word(words_size_pointer,f, x, words);
        x = strtok(NULL, " ");
    }   
}


void readline(FILE *f_two, FILE *f, char** words, int* words_size_pointer){
    char *line;
    size_t len = 0;
    ssize_t temp;
    int count;
    do{
    temp = getline(&line,&len,f);
    printf("%s", line);
    if(temp!= -1){
        sep_words(words, line, words_size_pointer, f_two);

    }
    }while(temp!=-1);

}


int main(int argc, char *argv[]){
    int x;
    int i;
    int j;
    x = strlen(argv[1]);
    char fi[x];
    char mtf[3] = "mtf";
    FILE *f;
    FILE *f_two;
    for(j = 0; j<(x-3); j++){
       fi[j] = argv[1][j];
    }
    strcat(fi, mtf);
    f = fopen(argv[1], "r");
    f_two = fopen(fi, "w");
    fputc(0xFA, f_two);
    fputc(0XCE, f_two);
    fputc(0XFA, f_two);
    fputc(0XDF, f_two);
    if(f == NULL){
        return 1;
    }

    char** words;
    words = (char **) malloc(20);
    for(i = 0; i<20; i++){
        words[i] = (char*) malloc(120);
    }
    int words_size = 20;
    int* words_size_pointer = &words_size;

    readline(f_two, f, words, words_size_pointer);
    return 0;
}

至于GDB错误:

    *** Error in `/file_loc/mtfcoding2': realloc(): invalid next size: 0x0000000000603490 ***
2040 \\This is due to print statements within my function.
Program received signal SIGABRT, Aborted.
0x00007ffff7a4acc9 in __GI_raise (sig=sig@entry=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56  ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.

感谢您的时间!:)

Answer 1

malloc并realloc要求字节数作为参数.但是你编写的代码如下:

char** words;
words = (char **) malloc(20);
for(i = 0; i<20; i++){
    words[i] = (char*) malloc(120);

你分配20字节,但然后你写了20个指针(可能需要80字节).要解决此问题,您需要计算存储20个指针所需的字节数.这样做的一种安全方法是使用SO推荐的malloc:

words = malloc(20 * sizeof *words);

您的realloc通话中存在同样的问题.

这条线没有效果:words_size_pointer = &temp;.也许你的意思*words_size_pointer = temp;.确保你清楚地理解这两行之间的区别.

NB.可能还有其他错误.