Use "free(p)" instead of "if (p != NULL) free(p)"

[Hephi]

Hi, in an attempt to clean up my code as I'm getting closer to putting up a first version of my AI I was studying the style guideline.http://wiki.openttd.org/Coding_style

At a certain point it talks about: Use "free(p)" instead of "if (p != NULL) free(p)"
and I was wondering if that's some C++ left in the guideline or if it's actually squirrel.
Also, what does it do exactly? Is it the same as putting free = null; in the code?

I tried searching but only thing I can find is about free variables which is not the same.
I include it anyway because I think it's nifty and would like to try and use it once.

Free variables
Free variables are variables referenced by a function that are not visible in the function scope. In the following example the function foo() declares x, y and testy as free variables.

Code: Select all

local x=10,y=20
testy <- “I’m testy”

function foo(a,b):(x,y,testy)
{
    ::print(testy);
    return a+b+x+y;
}

The value of a free variable is frozen and bound to the function when the function is created; the value is passed to the function as implicit parameter every time is called.

[Yexo]

The style guide you link to is about the OpenTTD code (which is C++), it has no relation at all with any NoAI code you write. Of course you can use it also for your AI project, but whether you do so is completely up to you. If you do, ignore those parts which are not applicable (like the part about free).

In C++, free(p) is different from p=NULL;

[Hephi]

k, thanks for the answer

[Lord Aro]

WARNING: N00bish question approaching!

In C++, free(p) is different from p=NULL;

How so?

[Rubidium]

How so?

free(p) is like removing wallpaper, p=NULL is like putting wallpaper over other wallpaper. With free(p) the old wallpaper is gone, with p=NULL the old wallpaper is still there you just can't access it anymore (ever).

[Lord Aro]

How so?

free(p) is like removing wallpaper, p=NULL is like putting wallpaper over other wallpaper. With free(p) the old wallpaper is gone, with p=NULL the old wallpaper is still there you just can't access it anymore (ever).

so with p=NULL, the original variable can possibly be found, but with free(p), it's eradicated from existence?

[Brumi]

Something like that, but most importantly, with p = NULL, your object remains in the memory, thus causing a memory leak. Practically you cannot find p anymore because you've lost all your references to it. free(p) frees the memory associated to p, and your object is eradicated from existence.