Name
	n3522, alx-0005r1 - sizeof(void) == 1

Principles
	-  Codify existing practice to address evident deficiencies.

Category
	Pointer arithmetic

Author
	Alejandro Colomar <alx@kernel.org>

History
	<https://www.alejandro-colomar.es/src/alx/alx/wg14/alx-0005.git/>

	r0 (2025-03-16):
	-  Initial draft.

	r1 (2025-03-16):
	-  Present as n3522.

Description
	Pointer arithmetic on 'void *' allows implementing certain
	operations more simply, by not having to convert pointers to
	'unsigned char *' and back.

	GNU C provides this as an extension which is widely used.

Future directions
	This may allow extending the language so that one can declare
	memcpy(3) et al. using array parameters:

		void *
		memcpy(size_t n;
		    void dst[n], void src[n], size_t n);

		// Since sizeof(void) == 1, this means n bytes available.

	which would help bounds checking.

Proposed wording
	Based on N3467.

    6.5.4.5  Unary operators :: The sizeof, _Lengthof, and alignof operators
	@@ Semantics, p4
	 When sizeof is applied to an operand that has type
	 char,
	 unsigned char,
	-or
	 signed char,
	+or void,
	 (or a qualified version thereof)
	 the result is 1.

    6.5.7  Additive operators
	@@ Constraints, p2
	 For addition,
	 either both operands shall have arithmetic type,
	 or one operand shall be
	 a pointer to a compete obect type
	+or a pointer to void
	 and the other shall have integer type.

	@@ p3
	 For subtraction,
	 one of the following shall hold:
		--  both operands have arithmetic type;
		--  both operands are
		    pointers to qualified or unqualified versions of
		    compatible object types;
	+	--  both operands are
	+	    pointers to qualified or unqualified versions of void; 
		    or
		--  the left operand is
		    a pointer to a complete object type
	+	    or a pointer to void
		    and the right operand has integer type.