Question

我试图在C中编写一个程序，该程序从用户那里获取未知数量的字符串（每个都是未知大小）作为输入并存储它们，然后在用户输入完字符串后打印它们。

首先，我使用指向字符指针（char **字符串）的指针，并使用malloc为其分配1个char *大小的内存块。然后我将1个字符大小的块分配给字符串指向的指针（（字符串）），同时使用malloc。从那里我使用一个名为get_String（）的用户定义函数从用户输入一个字符串输入，并将它放入char * 字符串指向的char指针。然后我使用for循环继续为char **字符串分配额外的char *内存，并为新指针分配1个内存char。

但是，我在for循环的第二次迭代中遇到错误，在line strings =（char **）realloc（strings，index + 1）;并且我收到错误消息：堆00558068处的块阻止在00558096处修改过去请求的大小为26.看起来我正在将已分配的内存写入char **字符串，但我不知道我在哪里或如何做此

这是我的整个代码：

#include "stdio.h"
#include "string.h"
#include "stdlib.h"

void get_strings( char* strings); // function to take in a string of an unknown size

int main( void )
{
    char** strings;
    int index, count;

    (strings) = (char**) malloc( sizeof(char*)); // this is the pointer that holds the addresses of all the strings
    *strings = (char*) malloc( sizeof(char)); // the address of the first string

    printf( "Enter a list of stringss. Quit by pressing enter without entering anything\n" );

    get_strings( *strings );

    for( index = 1; strlen(*(strings+index-1))!=1; index++) // stores strings from the user until they enter a blank line which is detected when string length is 1 for the \n
    {
        strings = (char**) realloc (strings, index+1); // adds an extra character pointer for another string
        *(strings + index) = (char*) malloc(sizeof(char)); // allocates memory to the new character pointer 


        get_strings( *(strings + index) ); // stores the string from the user
    } 

    printf( "You entered:\n" );

    for( count = 0; strlen(*(strings + count)) != 1; count++ ) //prints every string entered by the user except for the terminating blank line
    {
        printf( "%s", *(strings + count ) );
        free( *(strings + count ));
    }

    free( strings );


    system( "PAUSE" );
    return 0;
}

void get_strings( char* strings )
{
    fgets( strings, 1, stdin ); 

    while( strings[ strlen( strings ) - 1 ] != '\n' )
    {
        strings = (char*) realloc( strings, strlen(strings)+2 );
        fgets( strings + strlen(strings), 2, stdin ); 
    }

}

如前所述，在执行行时，for循环的第二次迭代发生堆块：strings =（char **）realloc（strings，index + 1）;

for( index = 1; strlen(*(strings+index-1))!=1; index++) // stores strings from the user until they enter a blank line which is detected when string length is 1 for the \n
    {
        strings = (char**) realloc (strings, index+1); // error occurs here
        *(strings + index) = (char*) malloc(sizeof(char)); // allocates memory to the new character pointer

如果有人能向我解释这个错误的原因以及解决问题的方向，我将非常感激。谢谢。

Answer 1

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

char *get_strings(void);

int main( void ){
    char **strings = NULL;
    char *string;
    int index, count;

    printf( "Enter a list of stringss. Quit by pressing enter without entering anything\n" );

    for(index = 0; string = get_strings(); ++index){
        strings = (char**) realloc (strings, (index+1)*sizeof(*strings));
        strings[index] = string;
    }
    printf( "You entered:\n" );

    for( count = 0; count < index; ++count ){
        printf("%s\n", strings[count]);
        free( strings[count] );
    }
    free( strings );

    system( "PAUSE" );
    return 0;
}

char *get_strings(void){
    char *string = NULL;//or calloc(1,sizeof(char)) for return "" (test by caller: *string == '\0')
    int ch;
    size_t len = 0;

    while(EOF != (ch=fgetc(stdin)) && ch != '\n' ) {
        string = (char*)realloc( string,  len + 2);//To realloc to each character is inefficient
        string[len++] = ch;
    }
    if(string)
        string[len] = '\0';
    return string;//The value is NULL when there is no input substantial.
}

C程序存储来自用户的未知数量的未知大小的字符串 - 堆块00558068修改为00558096过去请求的大小为26

1 个答案: