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);
}

Where is the definition of "NO"? Also, don't cast malloc: stackoverflow.com/questions/1565496/… . It's dangerous. — rost0031
– rost0031, Commented May 13, 2015 at 0:14
How is it not working? If there's an error message, please include it in the question. — Keith Thompson
– Keith Thompson, Commented May 13, 2015 at 1:28
"THE PROBLEM WAS THIS ASTERISK RIGHT BEFORE AUX" - so precisely what Ken's answer described (sigh). — WhozCraig
– WhozCraig, Commented May 13, 2015 at 2:19

Ken Y-N · Accepted Answer · 2015-05-13 00:18:49Z

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.

answered May 13, 2015 at 0:18

Ken Y-N

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1 Comment

Cris Barbosa Over a year ago

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

iammowgli · Accepted Answer · 2015-05-13 01:37:39Z

0

Try the following:

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

answered May 13, 2015 at 1:37

iammowgli

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