### 4.15 Architecture

- The values or expressions assigned to the macros specified in the headers `<float.h>`, `<limits.h>`, and `<stdint.h>` (C90, C99 and C11 5.2.4.2, C99 7.18.2, C99 7.18.3, C11 7.20.2, C11 7.20.3).

  Determined by ABI.

- The result of attempting to indirectly access an object with automatic or thread storage duration from a thread other than the one with which it is associated (C11 6.2.4).

  Such accesses are supported, subject to the same requirements for synchronization for concurrent accesses as for concurrent accesses to any object.

- The number, order, and encoding of bytes in any object (when not explicitly specified in this International Standard) (C99 and C11 6.2.6.1).

  Determined by ABI.

- Whether any extended alignments are supported and the contexts in which they are supported (C11 6.2.8).

  Extended alignments up to 2^{28} (bytes) are supported for objects of automatic storage duration. Alignments supported for objects of static and thread storage duration are determined by the ABI.

- Valid alignment values other than those returned by an _Alignof expression for fundamental types, if any (C11 6.2.8).

  Valid alignments are powers of 2 up to and including 2^{28}.

- The value of the result of the `sizeof` and `_Alignof` operators (C90 6.3.3.4, C99 and C11 6.5.3.4).

  Determined by ABI.