Code give me segmentation fault - c

Question

I don't know why my code gives me a segmentation fault.
Before it worked fine, so i must have done something to it,
but I don't know what.
This function gets some Markdown-Elements from a specific line in a file
and returns a dynamic array ( int * elements) with the elements
int * parser_getElements(char * string)
{
int * elements;
char * token, * temptoken;
int charcount = 0, elemcount = 1, i = 0;
assert(string != NULL);
elements = malloc(sizeof(int));
*elements = 0;
token = strtok(string," ");
while(token != NULL)
{
temptoken = token;
while (*temptoken)
{
charcount++;
++temptoken;
}
if(token[0] == '*' && token[charcount - 1] == '*')
{
if(token[1] == '*' && token[charcount - 2] == '*')
{
elements[elemcount-1] = EMPH;
}
else
{
if(token[1] != '*' && token[charcount - 2] != '*')
{
elements[elemcount-1] = ITAL;
}
}
elemcount++;
elements = realloc(elements,sizeof(int) * elemcount);
}
else if(token[0] == '_' && token[charcount - 1] == '_')
{
if(token[1] == '_' && token[charcount - 2] == '_')
{
elements[elemcount-1] = EMPH;
}
else
{
if(token[1] != '_' && token[charcount - 2] != '_')
{
elements[elemcount-1] = ITAL;
}
}
elemcount++;
elements = realloc(elements,sizeof(int) * elemcount);
}
else
{
elements[elemcount-1] = TEXT;
elemcount++;
elements = realloc(elements,sizeof(int) * elemcount);
}
token = strtok(NULL, " ");
charcount = 0;
}
return elements;
}
The problem occurs in the function below.
void parser_printMDElements(List markdown, FILE * out)
{
MD_Element element;
int count = 0, no_text = 0;
if(markdown != NULL)
{
element = markdown->value->elements[0];
while(element <= EMPH)
{
if(element > TEXT)
{
no_text = 1;
}
count++;
element = markdown->value->elements[count];
}
count = 0;
element = markdown->value->elements[0];
while(element <= EMPH)
{
if(no_text)
{
printf("%s\n",MD_Element_Descr[element]);
}
count++;
element = markdown->value->elements[count];
}
parser_printMDElements(markdown->next,out);
}
}
This line(first appearance)
element = markdown->value->elements[0];
gives me a segmentation fault and I don't know why.
The program stops after this line.
This is the main program
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "errors.h"
#include "parser.h"
int main(int argc, char * argv[])
{
Errorcode error = ERR_NULL;
char * gap;
int gapcount = 1;
List md = parser_newList();
/** Save name of document in firstnode */
md->value = malloc(sizeof(struct NodeValue));
md->value->string = argv[1];
md->type = DOCUMENT;
md->next = malloc(sizeof(struct Node));
error = parser_parseFile(argv[1],&(md->next));
if(error == ERR_NULL)
{
gap = malloc(sizeof(char));
*gap = '\0';
parser_printMDElements(md, gap, gapcount, stdout);
printf("\n");
}
return 0;
}
This code is extracted from parser.h
enum MD_Element
{
DOCUMENT,
LINE,
SECTION,
LISTELEMENT,
H1,
H2,
H3,
H4,
H5,
H6,
TEXT,
IMG,
LINK,
QUOTE,
CODE,
ITAL,
EMPH
};
typedef enum MD_Element MD_Element;
typedef struct NodeValue * NodeValue;
struct NodeValue
{
char * string;
int * elements;
};
typedef struct Node * Node;
struct Node
{
MD_Element type;
NodeValue value;
Node next;
};
typedef Node List;
Can sb. tell me what I've done wrong?
Thanks!

Answer 1

There are still many pieces of your code missing here.
I'm guessing that your problem is possibly in md->value->string = argv[1];.
(athough your question does not show how you are using md->value->string).
If you attempt to change the contents of the memory pointed by md->value->string, then you will have a memory access violation, since this variable is pointing to a read-only memory segment.
If that is indeed the case, then you can solve it by replacing md->value->string = argv[1]; with:
md->value->string = malloc(strlen(argv[1])+1);
strcpy(md->value->string,argv[1]);