Malloc execution error

Question

I made this method for a test and for some reason the malloc is not working. When I comment it it does work, but otherwise it will just say the program has stopped working.

typedef struct {
 int NroUSP; // chave primária
 int curso;
 int estado;
 int idade;
 bool valido; // para exclusão lógica
} REGISTRO;
typedef struct s {
 int NroUSP; // chave primária
 int curso;
 int estado;
 int idade;
 bool valido;
 struct s* prox;
} NO;
typedef struct {
 NO* inicio;
} LISTA;

These are the structures I used ^

EDIT: THE PROBLEM WAS THIS ASTERISK RIGHT BEFORE AUX

void ex6(){
 REGISTRO* aux;
 FILE *arq = fopen("C:\\Users\\jujuc_000\\Desktop\\Teste\\dados.bin","rb");
 FILE *arq2 = fopen("C:\\Users\\jujuc_000\\Desktop\\Teste\\ex6.bin","wb");
 LISTA l;
 l.inicio = NULL;
 NO*p = (NO*)malloc(sizeof(NO)); // this is the test malloc
 if(arq){
 while(1==fread(&aux,sizeof(REGISTRO),1,arq)){
 /*p = (NO*)malloc(sizeof(NO)); // this is the one I want to keep
 p->NroUSP = aux->NroUSP;
 p->curso = aux->curso;
 p->estado = aux->estado;
 p->idade = aux->idade;
 p->valido = aux->valido;
 if(!l.inicio){
 l.inicio = p;
 }
 p=p->prox;*/
 }
 }
 fclose(arq);
 fclose(arq2);
}

• rost0031: Where is the definition of "NO"? Also, don't cast malloc: stackoverflow.com/questions/1565496/… . It's dangerous.
• Dinesh: Is it failing at malloc or at p=p->prox?
• Keith Thompson: How is it not working? If there's an error message, please include it in the question.
• WhozCraig: "THE PROBLEM WAS THIS ASTERISK RIGHT BEFORE AUX" - so precisely what Ken's answer described (sigh).

Answer 1

fread(&aux,sizeof(REGISTRO),1,arq) is most likely your problem; aux is a pointer to a REGISTRO, but you try to read in a full REGISTRO into it, which more than likely overwrites memory, causing the apparent malloc failure in the next line. Change the declaration to:

REGISTRO aux;

And things should work.

• Cris Barbosa: Nope :/ still not working. Plus I tried putting the malloc both inside and outside the loop, and neither works.

Answer 2

Try the following:

1. Use feof() instead of if(arq) ...
2. Set p->prox = NULL;
3. Either declare 'REGISTRO aux' or allocate memory to 'aux' if declaring it as a pointer.