Manipulating pointer values inside functions taking pointers as arguments

Question

I have read a lot of questions of stackoverflow, but couldn't find any solutions on how to deal with this problem of allocating and manipulating pointers inside functions: Can anybody please tell me what's wrong with this code? (I want to allocate and assign values to *D through pointerpass and print the same through pointerprint)

#include<stdio.h>
#include<stdlib.h>

float *D;

void pointerpass(float **ptr1)
{
    *ptr1=(float*)malloc(3*sizeof(float));
    *(ptr1+0)=1.33;
    *(ptr1+1)=2.33;
    *(ptr1+2)=3.33;
}

void pointerprint(float **ptr2)
{
    int j=0;
    for (j=0;j<3;j++)
        printf("\n%f\n",*(ptr2+j));
}

int main() 
{
    pointerpass(&D);
    pointerprint(&D);
    return 0;
}

And why are you making life so difficult. You can pass back the result of malloc] — Ed Heal
– Ed Heal, Commented Jun 29, 2014 at 19:51
In C, *ptr1=(float*)malloc(3*sizeof(float)); - the (float*) cast is redundant. — Johann Gerell
– Johann Gerell, Commented Jun 29, 2014 at 19:52

Ed Heal · Accepted Answer · 2014-06-29 20:19:51Z

1

Here we go

#include<stdio.h>
#include<stdlib.h>

float * pointerpass(){
   float *ret = malloc(3*sizeof(float));
   ret[0] = 1.33f;
   ret[1] = 2.33f;
   ret[2] = 3.33f;
   return ret;
}
void pointerprint(float *array) {
    int j=0;
    for (j=0;j<3;j++) {
        printf("\n%f\n",array[j]);
    }
}

int main() {
   float *x = pointerpass();
   pointerprint(x);
   free(x); // We do not like memory leaks
   return 0;
}

answered Jun 29, 2014 at 20:19

Ed Heal

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1 Comment

G.One Over a year ago

Finally understood it!! Thanks a lot.

BLUEPIXY · Accepted Answer · 2014-06-29 19:54:31Z

0

void pointerpass(float **ptr1){
    *ptr1=(float*)malloc(3*sizeof(float));
    (*ptr1)[0]=1.33;
    (*ptr1)[1]=2.33;
    (*ptr1)[2]=3.33;
}
void pointerprint(float **ptr2){
    int j=0;
    for (j=0;j<3;j++)
        printf("\n%f\n", (*ptr2)[j]);
}

answered Jun 29, 2014 at 19:54

BLUEPIXY

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4 Comments

BLUEPIXY Over a year ago

Programming language can be represented exactly.

G.One Over a year ago

@Deduplicator why can't we cast malloc?

BLUEPIXY Over a year ago

@user3748848 , No problem just redundant it simply correct case. But cast it wrong often human error is made. Not required even though do it.

BLUEPIXY Over a year ago

Well, it is not a code of enough explanation needed exaggerated. ;D

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