allocation dynamic

**k4z1nh0** · 03-06-2005

hi.
my ask is this:
when i alloc memory in my code with function malloc of library <stdlib.h>
and i going use him...this not work...look my code testing malloc:

Code:

#include<stdio.h>
#include<stdlib.h>
int main(){
        int *p,
        num;
        char *entrada;
        p = (int *)malloc(sizeof(int));
        printf("\nquantos caracters deseja entrar? ");
        scanf("%d",&num);
        entrada = (char *)malloc(sizeof(char)*num);
        if (p == NULL)
        {
                printf("ERRO: Sem memoria!\n");
                return 1;
        }
        printf("Insira um valor:");
        scanf("%d",p);
        printf("Digite uma string:");
        fgets(entrada,num,stdin);
        printf("Voce Entrou com o valor %d\n",*p);
        printf("Voce digitou a string %s\n",entrada);
        free(p);
        free(entrada);
        return(0);
}

if anyone know, please answerme.

One kiss in your asses.

**k4z1nh0** · 03-06-2005

sorry here go the code correct that generate error.

Code:

#include<stdio.h>
#include<stdlib.h>
int main(){
        int *p,
        num;
        char *entrada;
        p = (int *)malloc(sizeof(int));
        printf("\nquantos caracters deseja entrar? ");
        scanf("%d",&num);
        entrada = (char *)malloc(sizeof(char)*num);
        if (p == NULL)
        {
                printf("ERRO: Sem memoria!\n");
                return 1;
        }
        printf("Insira um valor:");
        scanf("%d",p);
        printf("Digite uma string:");
        fgets(entrada,num,stdin);
        printf("Voce Entrou com o valor %d\n",*p);
        printf("Voce digitou a string %s\n",*entrada);
        free(p);
        free(entrada);
        return(0);
}

**Dave_Sinkula** · 03-06-2005

Wrong:

Code:

        printf("Voce digitou a string %s\n",*entrada);

Here *entrada is a single character, but %s expects a pointer to a string.

Code:

        printf("Voce digitou a string %s\n",entrada);

You may want to visit the FAQ.

**Thantos** · 03-06-2005

There is no need to cast the return of malloc.

**hk_mp5kpdw** · 03-06-2005

1. Unlike p, you do not check if the allocation of memory for entrada was a success.

2. You ask the user how many characters they wish to enter, you allocate this num bytes of memory for entrada, then you use fgets which only reads num - 1 characters (it has to save the last one for the NULL terminator). Is this a problem?

3.

Originally Posted by k4z1nh0

One kiss in your asses.

Uhhh... same to you buddy?!?!

**k4z1nh0** · 03-07-2005

thks, but the problem persists and problem not is in NULL TERMINATOR, the point is:
when the program askme "Digite uma String: ", the correct will be if he showme a cursor posicioned right of this string waiting what i want to do.
------------------
When he showme "Digite uma String: ", the next instruction will be fgets(entrada,sizeof(char)*80-1,stdin); ok??
when he showme the string above he jump to next function that is printf("Voce Entrou com o valor %d\n",*p);
he jump the function that i waited.WHY?? if there are one tutorial of Allocation Dynamid please post here pls.

Any help me?

**Dave_Sinkula** · 03-07-2005

Originally Posted by k4z1nh0

he jump the function that i waited.WHY??

Because scanf("%d",...) doesn't do anything with the newline in the input buffer, so it is still there and immediately satisifies the subsequent call to fgets.

http://faq.cprogramming.com/cgi-bin/...&id=1043284392

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