C code to reverse a string - including NULL character at the end of string -

1.) possible reverse string including null character (which means “abcd” represented 5 characters, including null character.)

2.) in current implementation, doesn't take 1.) account, getting segmentation error during swapping. ie while assigning: *str = *end;

void reverse(char *str)     {         char * end = str;         char tmp;         if (str)         {  // handle null string             while (*end)             {  // find end character                 ++end;             }             --end; // last meaningful element             while (str < end) // terminal condition: str , end meets in middle             {   tmp = *str; // normal swap subroutine                 *str = *end; // str advance 1 step                 *end = tmp;   // end 1 step                  str++;                 end-- ;             }         }         return;     } 

your function correct. seems problem trying reverse string literal. may not change string literals. immutable. attemp change string literal results in undefined behaviour of program.

from c standard (6.4.5 string literals)

7 unspecified whether these arrays distinct provided elements have appropriate values. if program attempts modify such array, behavior undefined

only take account better write

if ( *str ) 

instead of

 if (str) 

or if want check poinetr not null then

if ( str && *str ) 

in case decrement

--end; 

will valid if original string empty.

nevertheless function defined following way shown in demonstrative program

#include <stdio.h>  char * reverse( char *s ) {     char *last = s;      while ( *last ) ++last;      if ( last != s )     {                 ( char *first = s; first < --last; ++first )         {             char c = *first;             *first = *last;             *last = c;         }     }      return s; }      int main( void ) {     char s[] = "hello arshdeep kaur";      puts( s );     puts( reverse( s ) ); }     

the program output is

hello arshdeep kaur ruak peedhsra olleh