"Paranormal" activity in queue structure - c

Question

#include <stdio.h>
#include <stdlib.h>
/* Report an error and abort */
#define FATAL_ERROR(message) \
{ \
fprintf(stderr,"In %s(%d) [function %s]: %s\n", \
__FILE__, __LINE__, __FUNCTION__ , (message) ); \
abort(); \
} \
/* Report a posix error (similar to perror) and abort */
#define FATAL_PERROR(errcode) FATAL_ERROR(strerror(errcode))
void* Malloc(size_t n)
{
void* new = malloc(n);
if(new==NULL) FATAL_ERROR("Out of memory.");
return new;
}
typedef struct twit{
char data[141]; //contains the actual data
//struct twit *prev; //pointer to previous node (Closer to front)
struct twit *next; //pointer to next node (Closer to back)
}twit;
typedef struct twitbuffer{
twit *first;
twit *last;
int size;
}twit_buffer;
/*
function for create a new buffer
*/
void new_twitbuffer(twit_buffer *a)
{
a=Malloc(sizeof(twit)*12000);
a->first = a->last = NULL;
a->size = 0;
return;
}
int twitbuffer_empty(twit_buffer *a) {
if(a->first == NULL)
return 1;
else
return 0;
}
/*
function to insert a new twit in the buffer
*/
void insertTwit(twit_buffer *a, char *data)
{
twit new;
if (strlen(&data)<=140){
strcpy(&new.data,data);
}
else{
printf("Twit > 140 characters...");
}
if (new.data == NULL) {
//errno = ENOMEM;
printf("error!");
return;
}
if(a->first==NULL){
a->first = a->last = &new;
}else{
a->last->next=&new;
a->last=&new;
}
new.next= NULL;
a->size++;
return;
}
char* popTwit(twit_buffer *a) {
if (twitbuffer_empty(a)) {
return NULL;
}
char *data;
//strcpy(&data,a->first->data);
data=a->first->data;
if (a->first == a->last)
a->first = a->last = NULL;
else
a->first = a->first->next;
a->size--;
return data;
}
twit_buffer mytwitbuffer;
int main()
{
new_twitbuffer(&mytwitbuffer);
//printf("a=%d",mytwitbuffer);
char *a = "first twit\n";
char *b = "second twit\n";
char *c = "third twit\n";
insertTwit(&mytwitbuffer, a);
insertTwit(&mytwitbuffer, b);
insertTwit(&mytwitbuffer, c);
char *poppp;
poppp = popTwit(&mytwitbuffer);
printf("%s", poppp);
poppp = popTwit(&mytwitbuffer);
printf("%s", poppp);
poppp = popTwit(&mytwitbuffer);
printf("%s", poppp);
}
This is my code for an implementation of a queue. When i execute this i take this result:
thir�it
(null)(null)
This means that the two first insertions are not being done correctly and the third goes in stdout in a "paranormal" way! Do you have any ideas?

Answer 1

You are storing a reference to the local variable 'new' in your twit buffer. You should Malloc it, instead Of declaring It local