Name
	n3628, alx-0002r6 - Add operators _Minof and _Maxof

Principles
	-   Codify existing practice to address evident deficiencies.

Category
	New operators.

Author
	Alejandro Colomar <alx@kernel.org>

	Cc: Martin Uecker <uecker@tugraz.at>
	Cc: Joseph Myers <josmyers@redhat.com>

History
	<https://www.alejandro-colomar.es/src/alx/alx/wg14/alx-0002.git/>

	r0 (2025-03-08):
	-  Initial draft.

	r1 (2025-03-08):
	-  Fix typos.
	-  Add link to git repository in History.

	r2 (2025-03-09):
	-  Add 'See also' section.

	r3 (2025-03-09; n3518):
	-  Clarify the type of the expression yielded by _Minof, _Maxof.

	r4 (2025-05-31; n3573):
	-  Fix typos.

	r5 (2025-06-12):
	-  wfix
	-  ffix
	-  Rebase on N3550.

	r6 (2025-06-12; n3628):
	-  Split _Widthof to separate proposal (alx-0032).
	-  Move the operators to new subsection.
	-  Don't say the type of an operand type.

Description
	Many projects need to invent their own macros for getting
	information about a type.  Basic ones are MAXOF() and MINOF(),
	which get the maximum value of a type, and the minimum value of
	a type, respectively.

	Here are my own implementations:

	#define WIDTHOF(x)  (sizeof(x) * CHAR_BIT)
	#define SMAXOF(T)   ((T) (((((T) 1 << (WIDTHOF(T) - 2)) - 1) << 1) + 1))
	#define UMAXOF(T)   ((T) -1)
	#define IS_SIGNED(x)  ((typeof(x)) -1 < 1)
	#define MAXOF(T)    ((T) (IS_SIGNED(T) ? SMAXOF(T) : UMAXOF(T))
	#define MINOF(T)    ((T) ~type_max(T))

	As can be seen from my implementations, they are hard to write
	correctly, and review.  Also, now that we have bit-precise
	integers, one may want to get these to work with them, which
	would make it even harder to implement them.

	Also, since these are used more often in macros, we have the
	added problem of macros expanding arguments more than once
	(sometimes way more than once; sometimes resulting in macro
	 expansions in the order of megabytes of text).

	If these three were keywords, true operators, the compiler would
	evaluate arguments exactly once, and would return the right
	value, even for bit-precise integers.

	Since these macros are typically used with type names --not
	expressions--, this proposal suggests only allowing a type name
	as the operand.  It is left as a matter of QoI if compilers want
	to provide support for unary-expressions as with sizeof.

See also
	<https://github.com/llvm/llvm-project/issues/130429>
	<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119170>

Proposed wording
	Based on N3550.

    6.4.2  Keywords
	## Add _Minof, _Maxof.

    6.5.4.1  Unary operators :: General
	@@ Syntax, p1, unary-expression
	 alignof ( type-name )
	+_Minof ( type-name )
	+_Maxof ( type-name )

    6.5.4  Unary operators
	## New subsection after 6.5.4.5 ("The sizeof, _Countof, and alignof operators").

	+6.5.4.5+1  The _Minof and _Maxof operators
	+
	+Constraints
	+1
	+	The <b>_Minof</b> and <b>_Maxof</b> operators
	+	shall be applied to a parenthesized integer type.
	+
	+Semantics
	+2
	+	The <b>_Minof</b> and <b>_Maxof</b> operators yield
	+	the minimum and maximum value, respectively,
	+	that can be represented by the operand type.
	+	The operand is not evaluated,
	+	and the expression is an integer constant expression
	+	of the same type as its operand.

    6.6.1  Constant expressions :: General
	@@ Semantics, p8
	 alignof expressions,
	+_Minof expressions,
	+_Maxof expressions,
	 and floating,
	...
	 _Lengthof operator,
	-or alignof operator.
	+alignof operator,
	+_Minor operator,
	+or _Maxof operator.

	Update footnote 116?

	@@ p10
	...
	 _Lengthof operator,
	-or alignof operator.
	+alignof operator,
	+_Minor operator,
	+or _Maxof operator.

    6.7.7.3  Declarators :: Array declarators
	@@ Semantics, p5
	...
	 Where a size expression is part of the operand of
	-an alignof operator,
	+an alignof operator,
	+a _Minof operator,
	+or a _Maxof operator,
	 that expression is not evaluated.

    6.9.1  External definitions :: General
	@@ Constraints, p3
	 --  part of the operand of an alignof operator
	     which is an integer constant expression;
	+--  part of the operand of a _Minof operator;
	+--  part of the operand of a _Maxof operator;
	 --  part of the controlling expression of a generic selection;

	@@ Semantics, p5
	 or alignof operator
	-that is an integer constant expression),
	+that is an integer constant expression,
	+or part of a
	+_Minof,
	+or _Maxof
	+operator),
	 somewhere in the entire program

    A.2.2  Language syntax summary :: Lexical grammar :: Keywords
	Update.

    A.3.1  Language syntax summary :: Phrase structure grammar :: Expressions
	Update 6.5.4.1.

    J.3.16  Portability issues :: I-d behavior :: Architecture
	Update 7.

    J.6.2  P. I. :: Reserved IDs and keywords :: Rule based identifiers
	Update 2.