程序报段错误_markdown编辑

在代码第51行 *str = *next 处报错：Program received signal SIGSEGV, Segmentation fault

描述如下：

编写一个函数，删除一个字符串的一部分。函数原型如下：

int del_substr (char *str, char const *substr)

举个例子，假定str指向ABCDEFG. 如果substr指向FGH, CDF或XABC, 函数应该返回0，str未做任何修改。但如果substr指向CDE, 函数就把str修改为指向ABFG.

代码实现如下：

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

/*
** If the string "substr" appears in "str", delete it.
*/
//#define NULL 0 /* null pointer */
//#define NUL ’\0’ /* null byte */
#define TRUE 1
#define FALSE 0
/*
** See if the substring beginning at ’str’ matches the string ’want’.  If
** so, return a pointer to the first character in ’str’ after the match.
*/
char *match (char *str, char const *want)
{
    while (*want != '\0') {
        if (*str++ != *want++) {
            return NULL;
        }
    }
    return str;
}

int del_substr (char *str, char const *substr)
{
    char *next = NULL;
    char *res = str;
    /*
    ** Look through the string for the first occurrence of the substring.
    */
    while( *str != '\0' ){
       next = match( str, substr );
        if( next != NULL )
            break;
        str++;
    }
    printf("##next: %s\n", next);
    printf("##str: %s\n", str);
    printf("##res: %s\n", res);
    /*
    ** If we reached the end of the string, then the substring was not
    ** found.
    */
    if( *str == '\0' )
        return FALSE;
    /*
    ** Delete the substring by copying the bytes after it over the bytes of
    ** the substring itself.
    */
    while(*next != '\0'){
        *str = *next;
        printf("##str: %s\n", str);
        printf("##next: %s\n", next);
        str++;
        next++;
    }
    *str = '\0';
    printf("after del_substr result: %s\n", res);
    return TRUE;
}

int main()
{
    char str[] = "ABCDEFG";
    char const sub_str1[] = "FGH";
    char const sub_str2[] = "DE";
    int res = -1;
   // *str = 'a';
   // *(str+1) = 'b';
    printf("str: %s\n", str);
    res = del_substr(str, sub_str2);
   // printf("the resust is %s\n", str);
    printf("the res is %d\n", res);
    return res;
}

gdb调试报错如下

38        printf("##next: %s\n", next);
(gdb)
##next: FG
39        printf("##str: %s\n", str);
(gdb)
##str: DEFG
44        if( *str == '\0' )
(gdb)
50        while(*next != '\0'){
(gdb)
51            (*str) = (*next);
(gdb)
Program received signal SIGSEGV, Segmentation fault.
0x0804849f in del_substr (str=0x8048667 "DEFG", substr=0x8048670 "DE")
at del_substr.c:51
51            (*str) = (*next);
(gdb)

--------------------------------分割线--------------------------------
知道问题出在哪里了
main函数最开始的变量初始化
char *str = "ABCDEFG";
str指向的是只读常量区，所以执行到 *str = *next;会报错，该语句试图改变只读常量区里的值时，操作系统向程序发送了一个信号，告诉程序操作系统检测到了非法的内存访问，为了防止内存空间被破坏，操作系统提前终止了该程序的运行；
用数组声明即可
char str[] = "ABCDEFG";