c - Segmentation fault on reverse string function -

c - Segmentation fault on reverse string function -

i'm trying write simple function reverses string:

#include <stdio.h> #include <string.h> #include <stdlib.h> char* reversestr(char*s) { int slen=strlen(s); int i; char temp; (i=0;i<(slen/2);i++) { //swap temp=s[i]; s[i]=s[slen-i-1]; s[slen-i-1]=temp; } homecoming s; } main() { int num=64; char*str; str[0]='a'; *(str+1)='b'; *(str+2)='\0'; printf("%s %d %s" ,str,strlen(str),reversestr(str)); }

when phone call function reason segmentation fault core dumped error. can't spot place caused. anyone?

your problem lies in how you're creating string in first place:

char*str; str[0]='a'; *(str+1)='b'; *(str+2)='\0';

the declaration of str gives arbitrary value dereferencing str[0] undefined behaviour.

you can prepare like:

char str[3]; str[0]='a'; *(str+1)='b'; *(str+2)='\0';

although i'm not sure why you're mixing dereferencing methods (base[idx] , *(base+idx)).

alternatively, seek more concise options of:

char str[3]; strcpy (str, "ab"); char str[] = "ab";

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