Printing a string in reverse using a linked list - c

Question

I build a program that takes a string from a command line and use a linked list to print it in reverse.
I am currently debugging my program and I am just completely stuck. I have a feeling most are memory related.
/*
Takes a string from the command line.
Makes a linked-list out of it in reverse order.
Traverse it to construct a string in reverse.
Clean up (release memory).
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct st_CharNode
{
char theChar;
struct st_CharNode *next;
} CharNode;
void reverseIt( char *stringbuffer );
int main( int argc, char *argv[] )
{
char *stringBuffer;
// Check number of user supplied arguments.
if( argc != 2 )
{
fprintf( stderr, "usage: %s string. This reverses the string "
"given on the command line\n" );
exit( -1 );
}
// Copy the argument so we can make changes to it
stringBuffer = malloc( strlen(argv[1]) );
strcpy( argv[1], stringBuffer );
// Reverse the string
reverseIt( stringBuffer );
// Print the reversed string
printf( "the reversed string is '%s'\n", *stringBuffer );
return 0;
}
// Build a linked list backwards, then traverse it.
void reverseIt( char *stringbuffer )
{
CharNode *head, *node;
char *scan, *stop;
// initialize local vars
head = node = NULL;
// find the start and end of the string so we can walk it
scan = stringbuffer;
stop = stringbuffer + strlen(stringbuffer) + 1;
// walk the string
while (scan < stop)
{
if (head == NULL)
{
head = malloc( sizeof(CharNode*) );
head->theChar = *scan;
head->next = NULL;
}
else
{
node = malloc( sizeof(CharNode*) );
node->theChar = *scan;
node->next = head;
head = node;
}
scan++;
}
// Re-point to the buffer so we can drop the characters
scan = stringbuffer;
// Traverse the nodes and add them to the string
while( head != NULL )
{
*scan = head->theChar;
free( head );
node = head->next;
head = node;
scan++;
}
// Release head
free( head );
}

Answer 1

An error I've seen is that you are using strcpy like this:
strcpy( argv[1], stringBuffer );
which copies the value of stringBuffer into argv[1], you should do it the other way around, like this:
strcpy( stringBuffer, argv[1]);
see the man page of strcpy for more information: http://linux.die.net/man/3/strcpy