I’m writing c code using wsl with gcc compiler.And I tried to delete a space in front of a c-string with strcpy and got a strange result.
The string I tried to modify is s = {‘ ‘,’e’,’h’,’c’,’o’ ,’\0′};And I use a pointer temp to point at the "e"in the string and then I use strcpy(s,temp) to delete the space.BUT the result I get is ecoo,not echo.
#include <stdio.h>
#include <unistd.h>
#include <string.h>
int main(){
char a[256];
a[0] = ' ';
a[1] = 'e';
a[2] = 'h';
a[3] = 'c';
a[4] = 'o';
a[5] = '\0';
char* temp = a;
temp ++ ;
printf("%s\n",temp);
strcpy(a,temp);
printf("%s\n",a);
}
I tried to debug in the program and temp is indeed "echo"but the result is ecoo.
The code went as expected in the windows system in visual studio and vscode.
And I also tried different string length and I found out the code went well when the length of the string is 3,7.
enter image description here
>Solution :
Your code is invalid. From https://en.cppreference.com/w/c/string/byte/strcpy :
The behavior is undefined if the strings overlap.
temp is equal to a + 1 – they overlap. strcpy(a, a + 1) is not valid.