rust/helpers/build_assert.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/build_bug.h>
   4
   5 /*
   6  * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
   7  * use it in contexts where Rust expects a `usize` like slice (array) indices.
   8  * `usize` is defined to be the same as C's `uintptr_t` type (can hold any
   9  * pointer) but not necessarily the same as `size_t` (can hold the size of any
  10  * single object). Most modern platforms use the same concrete integer type for
  11  * both of them, but in case we find ourselves on a platform where
  12  * that's not true, fail early instead of risking ABI or
  13  * integer-overflow issues.
  14  *
  15  * If your platform fails this assertion, it means that you are in
  16  * danger of integer-overflow bugs (even if you attempt to add
  17  * `--no-size_t-is-usize`). It may be easiest to change the kernel ABI on
  18  * your platform such that `size_t` matches `uintptr_t` (i.e., to increase
  19  * `size_t`, because `uintptr_t` has to be at least as big as `size_t`).
  20  */
  21 static_assert(
  22         sizeof(size_t) == sizeof(uintptr_t) &&
  23         __alignof__(size_t) == __alignof__(uintptr_t),
  24         "Rust code expects C `size_t` to match Rust `usize`"
  25 );