patacongo commented on issue #740:
URL: https://github.com/apache/incubator-nuttx/issues/740#issuecomment-672929712
> but can we assume that `sizeof(FAR void *)` is always equals to
`sizeof(uintptr_t)` and `>= sizeof(uint32_t)`?
No. that is a false assumption. sizeof(uintptr) can be less than
sizeof(uint32_t).. On most 8-bit machines, sizeof(uintptr_t) is or should be 2
bytes. On ez80 it is either 2 or 3 bytes depending on mode. For ez80, you can
see:
In include/stdint.h:
/* Integer types capable of holding object pointers
* As a general rule, the size of size_t should be the same as the size
of
* uintptr_t: 32-bits on a machine with 32-bit addressing but 64-bits on
a
* machine with 64-bit addressing.
*/
typedef _ssize_t intptr_t;
typedef _size_t uintptr_t;
And in arch/z80/include/ez80/types.h:
/* These are the sizes of the standard integer types. NOTE that these
type
* names have a leading underscore character. This file will be included
* (indirectly) by include/stdint.h and typedef'ed to the final name
without
* the underscore character. This roundabout way of doings things allows
* the stdint.h to be removed from the include/ directory in the event
that
* the user prefers to use the definitions provided by their toolchain
header
* files
*
* These are the sizes of the types supported by the ZiLOG compiler:
*
* int - 24-bits
* short - 16-bits
* long - 32-bits
* char - 8-bits
* float - 32-bits
*/
...
/* A pointer is 2 or 3 bytes, depending upon if the ez80 is in z80
* compatibility mode or not
*
* Z80 mode - 16 bits
* ADL mode - 24 bits
*/
...
#elif defined(CONFIG_EZ80_Z80MODE)
typedef signed short _ssize_t;
typedef unsigned short _size_t;
#else
typedef signed int _ssize_t;
typedef unsigned int _size_t;
#endif
For AVR, the size of a pointer is different on the I-space bus and on the
D-space bus. As I recall, sizeof(FAR void *) is usualy 16-bits but might be as
much as 24-bits).
In fact sizeof(uinptr_t) < sizeof(uint32_t) is very common among the support
architecures. You must not use FAR void * as a container for arbitrary values.
You will break MANY architectures and we cannot permit you to do that.
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