malloc is the devil

hay, /prog/.

I'm creating a function which, given a pointer as an argument, creates memory for it (malloc) and then fills it with data (using a struct). This doesn't work, seemly because I'm doing the malloc inside the function itself, if I call malloc to the pointer in main, before calling the function, everything works fine.

Does this mean I can't pass a pointer to a function, malloc it inside there and be on my merry way when the function returns? Ouch. halp.

Of course you can do that. But you're probably doing it wrong.

lrn2 pass by value. Regardless, a function like that should simply return a pointer, not fuck with one passed in.

What? It sounds like you're doing this:

void foo(struct bar * ptr) {
    ptr = malloc(sizeof(struct bar));
    ptr->retarded = 1;
}

int main(void) {
    struct quux * mystruct;
    foo(mystruct);
}

Which is completely retarded.

>>4
I think he tries this:

#include <string.h>

struct howtofillstruct
{
    int charactertofill; /* Or whatever */
};

void create(char *input, size_t size, struct howtofillstruct howtofill)
{
    input = malloc(size);
    if(input)               /* if he does error handling at all */
        memset(input, howtofill.charactertofill, size);
}

int main(void)
{
    char *foo;
    struct howtofillstruct howtofill;

    howtofill.charactertofill = 'A';
    create(foo, 100, howtofill);

    printf("Foo is 0x%x.\n", foo);
    printf("Foo[0] contains %c.\n", foo[0]); /* segfault */

    return 0;
}

>>1
Try:

struct foo
{
    int bar;
};

main()
{
    struct foo* f;
    baz(&f);
    f->bar = 1;
    // etc
}

void baz(struct foo** f)
{
    *f = malloc(sizeof(foo));
}

>>6 illustrates the difference between pass by reference and pass by value. +1 experience points.

>>7 is a slashdot goon

>>7
It's still pass by value.

>>9
yes, yes, all it's pass by value.

>>9
don't confuse him more

ITT I HAVEN'T DISCOVERED A GARBAGE COLLECTOR YET

>>1
It should work, but...
YOU'RE DOING IT WRONG

>>9
Truth; it's particularly easy to see it in C

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