Messages in this thread | | | From | Linus Torvalds <> | Date | Sat, 23 Sep 2023 11:19:08 -0700 | Subject | Re: [PATCH v4] gpio: sim: fix an invalid __free() usage |
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On Tue, 19 Sept 2023 at 03:49, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > Nope, k*alloc*() returns ZERO or NULL on failure. That's what most developers > are missing :-)
Absolutely not.
k*alloc() returns NULL on failure. Absolutely nothing else.
On *success*, it can return the special ZERO_SIZE_PTR. But that is *not* a failure at all. It's very much a successful pointer.
Now, it's a pointer that you can't actually dereference, but that's very much intentional. You can't dereference it, because you asked for a zero-sized allocation. You got a zero-sized allocation.
But please never *ever* think it's a failure. It's very much not a failure case, and it is very much intentional.
It's different from NULL exactly *because* it's successful, and exactly so that you can write
ptr = kmalloc(size); if (!ptr) return -ENOMEM;
without having to worry about the "size is zero" case.
The standard user-space "malloc()" library is misdesigned. Surprise surprise. The kernel isn't.
Linus
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