Segmentation Fault, array of pointers

Question

Why do I get the Segmentation Fault error? I've documented a lot but couldn't clarify this.

char * sir=malloc(50*sizeof(char));
char * aux;
int i;

for(i=1;;i++)
{
    fgets(aux, 50, stdin);

    if(strcmp(aux,"END")==0)
        break;
    else
    {
        sir[i]=malloc(50 * sizeof(char));
        strcpy(aux,sir[i]);
    }
}

If I use static allocation, then I get an infinite loop.

1) not allocated for aux 2) fgets include newline. strcmp(aux,"END\n") instead of. 3) type of sir is char *. char ** sir=malloc(64*sizeof(char*)); instead of. and strcpy(aux,sir[i]); --> strcpy(sir[i],aux); — BLUEPIXY
– BLUEPIXY, Commented Dec 5, 2015 at 14:09

Vlad from Moscow · Accepted Answer · 2015-12-05 14:18:09Z

1

Pointer aux was not initialized and has indeterminate value

char * aux;

Thus in this loop the attempt to write data using the pointer

for(i=1;;i++)
{
fgets(aux, 50, stdin);
//...

results in undefined behaviour of the program.

Maybe it is a typo and you meant str instead of aux Nevertheless in any case this statement

sir[i]=malloc(50 * sizeof(char));

does not make sense.

Also this cpmparison is wrong

if(strcmp(aux,"END") == 0)

because the string read by using fgets can contain a new line character.

edited Dec 5, 2015 at 14:18

answered Dec 5, 2015 at 14:12

Vlad from Moscow

313k27 gold badges204 silver badges358 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Segmentation Fault, array of pointers

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related