<!doctype html><html lang="en">
 <head>
  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
  <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
  <title>P2537R2: Relax va_start Requirements to Match C</title>
<style data-fill-with="stylesheet">/******************************************************************************
 *                   Style sheet for the W3C specifications                   *
 *
 * Special classes handled by this style sheet include:
 *
 * Indices
 *   - .toc for the Table of Contents (<ol class="toc">)
 *     + <span class="secno"> for the section numbers
 *   - #toc for the Table of Contents (<nav id="toc">)
 *   - ul.index for Indices (<a href="#ref">term</a><span>, in § N.M</span>)
 *   - table.index for Index Tables (e.g. for properties or elements)
 *
 * Structural Markup
 *   - table.data for general data tables
 *     -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
 *     -> use <table class='complex data'> for extra-complex tables
 *     -> use <td class='long'> for paragraph-length cell content
 *     -> use <td class='pre'> when manual line breaks/indentation would help readability
 *   - dl.switch for switch statements
 *   - ol.algorithm for algorithms (helps to visualize nesting)
 *   - .figure and .caption (HTML4) and figure and figcaption (HTML5)
 *     -> .sidefigure for right-floated figures
 *   - ins/del
 *     -> ins/del.c### for candidate and proposed changes (amendments)
 *
 * Code
 *   - pre and code
 *
 * Special Sections
 *   - .note       for informative notes             (div, p, span, aside, details)
 *   - .example    for informative examples          (div, p, pre, span)
 *   - .issue      for issues                        (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *   - .correction for "candidate corrections"       (div, aside, details, section)
 *   - .addition   for "candidate additions"         (div, aside, details, section)
 *   - .correction.proposed for "proposed corrections" (div, aside, details, section)
 *   - .addition.proposed   for "proposed additions"   (div, aside, details, section)
 *
 * Definition Boxes
 *   - pre.def   for WebIDL definitions
 *   - table.def for tables that define other entities (e.g. CSS properties)
 *   - dl.def    for definition lists that define other entitles (e.g. HTML elements)
 *
 * Numbering
 *   - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
 *   - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
 *   - ::before styled for CSS-generated issue/example/figure numbers:
 *     -> Documents wishing to use this only need to add
 *        figcaption::before,
 *        .caption::before { content: "Figure "  counter(figure) " ";  }
 *        .example::before { content: "Example " counter(example) " "; }
 *        .issue::before   { content: "Issue "   counter(issue) " ";   }
 *
 * Header Stuff (ignore, just don't conflict with these classes)
 *   - .head for the header
 *   - .copyright for the copyright
 *
 * Outdated warning for old specs
 *
 * Miscellaneous
 *   - .overlarge for things that should be as wide as possible, even if
 *     that overflows the body text area. This can be used on an item or
 *     on its container, depending on the effect desired.
 *     Note that this styling basically doesn't help at all when printing,
 *     since A4 paper isn't much wider than the max-width here.
 *     It's better to design things to fit into a narrower measure if possible.
 *
 *   - js-added ToC jump links (see fixup.js)
 *
 ******************************************************************************/

/* color variables included separately for reliability */

/******************************************************************************/
/*                                    Body                                    */
/******************************************************************************/

	html {
	}

	body {
		counter-reset: example figure issue;

		/* Layout */
		max-width: 50em;			  /* limit line length to 50em for readability   */
		margin: 0 auto;				/* center text within page                    */
		padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
		padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag    */

		/* Typography */
		line-height: 1.5;
		font-family: sans-serif;
		widows: 2;
		orphans: 2;
		word-wrap: break-word;
		overflow-wrap: break-word;
		hyphens: auto;

		color: black;
		color: var(--text);
		background: white top left fixed no-repeat;
		background: var(--bg) top left fixed no-repeat;
		background-size: 25px auto;
	}


/******************************************************************************/
/*                         Front Matter & Navigation                          */
/******************************************************************************/

/** Header ********************************************************************/

	div.head { margin-bottom: 1em; }
	div.head hr { border-style: solid; }

	div.head h1 {
		font-weight: bold;
		margin: 0 0 .1em;
		font-size: 220%;
	}

	div.head h2 { margin-bottom: 1.5em;}

/** W3C Logo ******************************************************************/

	.head .logo {
		float: right;
		margin: 0.4rem 0 0.2rem .4rem;
	}

	.head img[src*="logos/W3C"] {
		display: block;
		border: solid #1a5e9a;
		border: solid var(--logo-bg);
		border-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		background: var(--logo-bg);
		color: white;
		color: var(--logo-text);
		font-weight: bold;
	}

	.head a:hover > img[src*="logos/W3C"],
	.head a:focus > img[src*="logos/W3C"] {
		opacity: .8;
	}

	.head a:active > img[src*="logos/W3C"] {
		background: #c00;
		background: var(--logo-active-bg);
		border-color: #c00;
		border-color: var(--logo-active-bg);
	}

	/* see also additional rules in Link Styling section */

/** Copyright *****************************************************************/

	p.copyright,
	p.copyright small { font-size: small; }

/** Back to Top / ToC Toggle **************************************************/

	@media print {
		#toc-nav {
			display: none;
		}
	}
	@media not print {
		#toc-nav {
			position: fixed;
			z-index: 3;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

			height: 1.33em;
			padding: .1em 0.3em;
			margin: 0;

			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;

			color: #707070;
			color: var(--tocnav-normal-text);
			background: white;
			background: var(--tocnav-normal-bg);
		}
		#toc-nav > a:hover,
		#toc-nav > a:focus {
			color: black;
			color: var(--tocnav-hover-text);
			background: #f8f8f8;
			background: var(--tocnav-hover-bg);
		}
		#toc-nav > a:active {
			color: #c00;
			color: var(--tocnav-active-text);
			background: white;
			background: var(--tocnav-active-bg);
		}

		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		/* statusbar gets in the way on keyboard focus; remove once browsers fix */
		#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
			padding-bottom: 1.5rem;
		}

		#toc-nav:not(:hover) > a:not(:focus) > span + span {
			/* Ideally this uses :focus-within on #toc-nav */
			display: none;
		}
		#toc-nav > a > span + span {
			padding-right: 0.2em;
		}
	}

/** ToC Sidebar ***************************************************************/

	/* Floating sidebar */
	@media screen {
		body.toc-sidebar #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			max-width: 80%;
			max-width: calc(100% - 2em - 26px);
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			color: black;
			color: var(--tocsidebar-text);
			background: inherit;
			background-color: #f7f8f9;
			background-color: var(--tocsidebar-bg);
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
			box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
		}
		body.toc-sidebar #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
			color: var(--tocsidebar-heading-text);
		}
		body.toc-sidebar #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	/* Hide main scroller when only the ToC is visible anyway */
	@media screen and (max-width: 28em) {
		body.toc-sidebar {
			overflow: hidden;
		}
	}

	/* Sidebar with its own space */
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			color: black;
			color: var(--tocsidebar-text);
			background: inherit;
			background-color: #f7f8f9;
			background-color: var(--tocsidebar-bg);
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
			box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
		}
		body:not(.toc-inline) #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
			color: var(--tocsidebar-heading-text);
		}

		body:not(.toc-inline) {
			padding-left: 29em;
		}
		/* See also Overflow section at the bottom */

		body:not(.toc-inline) #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) {
			margin: 0 4em;
		}
	}

/******************************************************************************/
/*                                Sectioning                                  */
/******************************************************************************/

/** Headings ******************************************************************/

	h1, h2, h3, h4, h5, h6, dt {
		page-break-after: avoid;
		page-break-inside: avoid;
		font: 100% sans-serif;   /* Reset all font styling to clear out UA styles */
		font-family: inherit;	/* Inherit the font family. */
		line-height: 1.2;		/* Keep wrapped headings compact */
		hyphens: manual;		/* Hyphenated headings look weird */
	}

	h2, h3, h4, h5, h6 {
		margin-top: 3rem;
	}

	h1, h2, h3 {
		color: #005A9C;
		color: var(--heading-text);
	}

	h1 { font-size: 170%; }
	h2 { font-size: 140%; }
	h3 { font-size: 120%; }
	h4 { font-weight: bold; }
	h5 { font-style: italic; }
	h6 { font-variant: small-caps; }
	dt { font-weight: bold; }

/** Subheadings ***************************************************************/

	h1 + h2,
	#profile-and-date {
		/* #profile-and-date is a subtitle in an H2 under the H1 */
		margin-top: 0;
	}
	h2 + h3,
	h3 + h4,
	h4 + h5,
	h5 + h6 {
		margin-top: 1.2em; /* = 1 x line-height */
	}

/** Section divider ***********************************************************/

	:not(.head) > :not(.head) + hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		color: black;
		color: var(--hr-text);
		border: transparent solid 0;
		background: transparent;
	}
	:not(.head) > hr::before {
		content: "\2727\2003\2003\2727\2003\2003\2727";
	}

/******************************************************************************/
/*                            Paragraphs and Lists                            */
/******************************************************************************/

	p {
		margin: 1em 0;
	}

	dd > p:first-child,
	li > p:first-child {
		margin-top: 0;
	}

	ul, ol {
		margin-left: 0;
		padding-left: 2em;
	}

	li {
		margin: 0.25em 0 0.5em;
		padding: 0;
	}

	dl dd {
		margin: 0 0 .5em 2em;
	}

	.head dd + dd { /* compact for header */
		margin-top: -.5em;
	}

	/* Style for algorithms */
	ol.algorithm ol:not(.algorithm),
	.algorithm > ol ol:not(.algorithm) {
	border-left: 0.5em solid #DEF;
	border-left: 0.5em solid var(--algo-border);
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	 padding: .5em;
	 border: thin solid #ddd;
	 border: thin solid var(--algo-border);
	 border-radius: .5em;
	 margin: .5em calc(-0.5em - 1px);
	}
	[data-algorithm]:not(.heading) > :first-child {
	 margin-top: 0;
	}
	[data-algorithm]:not(.heading) > :last-child {
	 margin-bottom: 0;
	}

	/* Style for switch/case <dl>s */
	dl.switch > dd > ol.only,
	dl.switch > dd > .only > ol {
	margin-left: 0;
	}
	dl.switch > dd > ol.algorithm,
	dl.switch > dd > .algorithm > ol {
	margin-left: -2em;
	}
	dl.switch {
	padding-left: 2em;
	}
	dl.switch > dt {
	text-indent: -1.5em;
	margin-top: 1em;
	}
	dl.switch > dt + dt {
	margin-top: 0;
	}
	dl.switch > dt::before {
	content: '\21AA';
	padding: 0 0.5em 0 0;
	display: inline-block;
	width: 1em;
	text-align: right;
	line-height: 0.5em;
	}

/** Terminology Markup ********************************************************/


/******************************************************************************/
/*                                 Inline Markup                              */
/******************************************************************************/

/** Terminology Markup ********************************************************/
	dfn   { /* Defining instance */
		font-weight: bolder;
	}
	a > i { /* Instance of term */
		font-style: normal;
	}
	dt dfn code, code.idl {
		font-size: inherit;
	}
	dfn var {
		font-style: normal;
	}

/** Change Marking ************************************************************/

	del {
		color: #aa0000;
		color: var(--del-text);
		background: transparent;
		background: var(--del-bg);
		text-decoration: line-through;
	}
	ins {
		color: #006100;
		color: var(--ins-text);
		background: transparent;
		background: var(--ins-bg);
		text-decoration: underline;
	}

	/* for amendments (candidate/proposed changes) */

	.amendment ins, .correction ins, .addition ins,
	ins[class^=c] {
		text-decoration-style: dotted;
	}
	.amendment del, .correction del, .addition del,
	del[class^=c] {
		text-decoration-style: dotted;
	}
	.amendment.proposed ins, .correction.proposed ins, .addition.proposed ins,
	ins[class^=c].proposed {
		text-decoration-style: double;
	}
	.amendment.proposed del, .correction.proposed del, .addition.proposed del,
	del[class^=c].proposed {
		text-decoration-style: double;
	}

/** Miscellaneous improvements to inline formatting ***************************/

	sup {
		vertical-align: super;
		font-size: 80%
	}

/******************************************************************************/
/*                                    Code                                    */
/******************************************************************************/

/** General monospace/pre rules ***********************************************/

	pre, code, samp {
		font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
		font-size: .9em;
		hyphens: none;
		text-transform: none;
		text-align: left;
		text-align: start;
		font-variant: normal;
		orphans: 3;
		widows: 3;
		page-break-before: avoid;
	}
	pre code,
	code code {
		font-size: 100%;
	}

	pre {
		margin-top: 1em;
		margin-bottom: 1em;
		overflow: auto;
	}

/** Inline Code fragments *****************************************************/

	/* Do something nice. */

/******************************************************************************/
/*                                    Links                                   */
/******************************************************************************/

/** General Hyperlinks ********************************************************/

	/* We hyperlink a lot, so make it less intrusive */
	a[href] {
		color: #034575;
		color: var(--a-normal-text);
		text-decoration: underline #707070;
		text-decoration: underline var(--a-normal-underline);
		text-decoration-skip-ink: none;
	}
	a:visited {
		color: #034575;
		color: var(--a-visited-text);
		text-decoration-color: #bbb;
		text-decoration-color: var(--a-visited-underline);
	}

	/* Indicate interaction with the link */
	a[href]:focus,
	a[href]:hover {
		text-decoration-thickness: 2px;
	}
	a[href]:active {
		color: #c00;
		color: var(--a-active-text);
		text-decoration-color: #c00;
		text-decoration-color: var(--a-active-underline);
	}

	/* Backout above styling for W3C logo */
	.head .logo,
	.head .logo a {
		border: none;
		text-decoration: none;
		background: transparent;
	}

/******************************************************************************/
/*                                    Images                                  */
/******************************************************************************/

	img {
		border-style: none;
	}

	img, svg {
		/* Intentionally not color-scheme aware. */
		background: white;
	}

	/* For autogen numbers, add
	  .caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
	*/

	figure, .figure, .sidefigure {
		page-break-inside: avoid;
		text-align: center;
		margin: 2.5em 0;
	}
	.figure img,	.sidefigure img,	figure img,
	.figure object, .sidefigure object, figure object {
		max-width: 100%;
		margin: auto;
		height: auto;
	}
	.figure pre, .sidefigure pre, figure pre {
		text-align: left;
		display: table;
		margin: 1em auto;
	}
	.figure table, figure table {
		margin: auto;
	}
	@media screen and (min-width: 20em) {
		.sidefigure {
			float: right;
			width: 50%;
			margin: 0 0 0.5em 0.5em;
		}
	}
	.caption, figcaption, caption {
		font-style: italic;
		font-size: 90%;
	}
	.caption::before, figcaption::before, figcaption > .marker {
		font-weight: bold;
	}
	.caption, figcaption {
		counter-increment: figure;
	}

	/* DL list is indented 2em, but figure inside it is not */
	dd > .figure, dd > figure { margin-left: -2em; }

/******************************************************************************/
/*                             Colored Boxes                                  */
/******************************************************************************/

	.issue, .note, .example, .assertion, .advisement, blockquote,
	.amendment, .correction, .addition {
		margin: 1em auto;
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	blockquote > :first-child,
	.note  > p:first-child,
	.issue > p:first-child,
	.amendment > p:first-child,
	.correction > p:first-child,
	.addition > p:first-child {
		margin-top: 0;
	}
	blockquote > :last-child,
	.note  > p:last-child,
	.issue > p:last-child,
	.amendment > p:last-child,
	.correction > p:last-child,
	.addition > p:last-child {
		margin-bottom: 0;
	}


	.issue::before, .issue > .marker,
	.example::before, .example > .marker,
	.note::before, .note > .marker,
	details.note > summary > .marker,
	.amendment::before, .amendment > .marker,
	details.amendment > summary > .marker,
	.addition::before, .addition > .marker,
	addition.amendment > summary > .marker,
	.correction::before, .correction > .marker,
	correction.amendment > summary > .marker
	{
		text-transform: uppercase;
		padding-right: 1em;
	}

	.example::before, .example > .marker {
		display: block;
		padding-right: 0em;
	}

/** Blockquotes ***************************************************************/

	blockquote {
		border-color: silver;
		border-color: var(--blockquote-border);
		background: transparent;
		background: var(--blockquote-bg);
		color: currentcolor;
		color: var(--blockquote-text);
	}

/** Open issue ****************************************************************/

	.issue {
		border-color: #e05252;
		border-color: var(--issue-border);
		background: #fbe9e9;
		background: var(--issue-bg);
		color: black;
		color: var(--issue-text);
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		color: #831616;
		color: var(--issueheading-text);
	}
	/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
	  or use class="marker" to mark up the issue number in source. */

/** Example *******************************************************************/

	.example {
		border-color: #e0cb52;
		border-color: var(--example-border);
		background: #fcfaee;
		background: var(--example-bg);
		color: black;
		color: var(--example-text);
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		color: #574b0f;
		color: var(--exampleheading-text);
	}
	/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
	  or use class="marker" to mark up the example number in source. */

/** Non-normative Note ********************************************************/

	.note {
		border-color: #52e052;
		border-color: var(--note-border);
		background: #e9fbe9;
		background: var(--note-bg);
		color: black;
		color: var(--note-text);
		overflow: auto;
	}

	.note::before, .note > .marker,
	details.note > summary {
		color: hsl(120, 70%, 30%);
		color: var(--noteheading-text);
	}
	/* Add .note::before { content: "Note "; } for autogen label,
	  or use class="marker" to mark up the label in source. */

	details.note[open] > summary {
		border-bottom: 1px silver solid;
		border-bottom: 1px var(--notesummary-underline) solid;
	}

/** Assertion Box *************************************************************/
	/*  for assertions in algorithms */

	.assertion {
		border-color: #AAA;
		border-color: var(--assertion-border);
		background: #EEE;
		background: var(--assertion-bg);
		color: black;
		color: var(--assertion-text);
	}

/** Advisement Box ************************************************************/
	/*  for attention-grabbing normative statements */

	.advisement {
		border-color: orange;
		border-color: var(--advisement-border);
		border-style: none solid;
		background: #fec;
		background: var(--advisement-bg);
		color: black;
		color: var(--advisement-text);
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement::before, .advisement > .marker {
		color: #b35f00;
		color: var(--advisementheading-text);
	}

/** Amendment Box *************************************************************/

	.amendment, .correction, .addition {
		border-color: #330099;
		border-color: var(--amendment-border);
		background: #F5F0FF;
		background: var(--amendment-bg);
		color: black;
		color: var(--amendment-text);
	}
	.amendment.proposed, .correction.proposed, .addition.proposed {
		border-style: solid;
		border-block-width: 0.25em;
	}
	.amendment::before, .amendment > .marker,
	details.amendment > summary::before, details.amendment > summary > .marker,
	.correction::before, .correction > .marker,
	details.correction > summary::before, details.correction > summary > .marker,
	.addition::before, .addition > .marker,
	details.addition > summary::before, details.addition > summary > .marker {
		color: #220066;
		color: var(--amendmentheading-text);
	}
	.amendment.proposed::before, .amendment.proposed > .marker,
	details.amendment.proposed > summary::before, details.amendment.proposed > summary > .marker,
	.correction.proposed::before, .correction.proposed > .marker,
	details.correction.proposed > summary::before, details.correction.proposed > summary > .marker,
	.addition.proposed::before, .addition.proposed > .marker,
	details.addition.proposed > summary::before, details.addition.proposed > summary > .marker {
		font-weight: bold;
	}

/** Spec Obsoletion Notice ****************************************************/
	/* obnoxious obsoletion notice for older/abandoned specs. */

	details {
		display: block;
	}
	summary {
		font-weight: bolder;
	}

	.annoying-warning:not(details),
	details.annoying-warning:not([open]) > summary,
	details.annoying-warning[open] {
		background: hsla(40,100%,50%,0.95);
		background: var(--warning-bg);
		color: black;
		color: var(--warning-text);
		padding: .75em 1em;
		border: red;
		border: var(--warning-border);
		border-style: solid none;
		box-shadow: 0 2px 8px black;
		text-align: center;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 0;
		right: 0;
		bottom: 2em;
		z-index: 1000;
	}
}

	details.annoying-warning:not([open]) > summary {
		text-align: center;
	}

/** Entity Definition Boxes ***************************************************/

	.def {
		padding: .5em 1em;
		background: #def;
		background: var(--def-bg);
		margin: 1.2em 0;
		border-left: 0.5em solid #8ccbf2;
		border-left: 0.5em solid var(--def-border);
		color: black;
		color: var(--def-text);
	}

/******************************************************************************/
/*                                    Tables                                  */
/******************************************************************************/

	th, td {
		text-align: left;
		text-align: start;
	}

/** Property/Descriptor Definition Tables *************************************/

	table.def {
		/* inherits .def box styling, see above */
		width: 100%;
		border-spacing: 0;
	}

	table.def td,
	table.def th {
		padding: 0.5em;
		vertical-align: baseline;
		border-bottom: 1px solid #bbd7e9;
		border-bottom: 1px solid var(--defrow-border);
	}

	table.def > tbody > tr:last-child th,
	table.def > tbody > tr:last-child td {
		border-bottom: 0;
	}

	table.def th {
		font-style: italic;
		font-weight: normal;
		padding-left: 1em;
		width: 3em;
	}

	/* For when values are extra-complex and need formatting for readability */
	table td.pre {
		white-space: pre-wrap;
	}

	/* A footnote at the bottom of a def table */
	table.def td.footnote {
		padding-top: 0.6em;
	}
	table.def td.footnote::before {
		content: " ";
		display: block;
		height: 0.6em;
		width: 4em;
		border-top: thin solid;
	}

/** Data tables (and properly marked-up index tables) *************************/
	/*
		<table class="data"> highlights structural relationships in a table
		when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)

		Use class="complex data" for particularly complicated tables --
		(This will draw more lines: busier, but clearer.)

		Use class="long" on table cells with paragraph-like contents
		(This will adjust text alignment accordingly.)
		Alternately use class="longlastcol" on tables, to have the last column assume "long".
	*/

	table {
		word-wrap: normal;
		overflow-wrap: normal;
		hyphens: manual;
	}

	table.data,
	table.index {
		margin: 1em auto;
		border-collapse: collapse;
		border: hidden;
		width: 100%;
	}
	table.data caption,
	table.index caption {
		max-width: 50em;
		margin: 0 auto 1em;
	}

	table.data td,  table.data th,
	table.index td, table.index th {
		padding: 0.5em 1em;
		border-width: 1px;
		border-color: silver;
		border-color: var(--datacell-border);
		border-top-style: solid;
	}

	table.data thead td:empty {
		padding: 0;
		border: 0;
	}

	table.data  thead,
	table.index thead,
	table.data  tbody,
	table.index tbody {
		border-bottom: 2px solid;
	}

	table.data colgroup,
	table.index colgroup {
		border-left: 2px solid;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		border-right: 2px solid;
		border-top: 1px solid silver;
		border-top: 1px solid var(--datacell-border);
		padding-right: 1em;
	}

	table.data th[colspan],
	table.data td[colspan] {
		text-align: center;
	}

	table.complex.data th,
	table.complex.data td {
		border: 1px solid silver;
		border: 1px solid var(--datacell-border);
		text-align: center;
	}

	table.data.longlastcol td:last-child,
	table.data td.long {
		vertical-align: baseline;
		text-align: left;
	}

	table.data img {
		vertical-align: middle;
	}


/*
Alternate table alignment rules

	table.data,
	table.index {
		text-align: center;
	}

	table.data  thead th[scope="row"],
	table.index thead th[scope="row"] {
		text-align: right;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		text-align: right;
	}

Possible extra rowspan handling

	table.data  tbody th[rowspan]:not([rowspan='1']),
	table.index tbody th[rowspan]:not([rowspan='1']),
	table.data  tbody td[rowspan]:not([rowspan='1']),
	table.index tbody td[rowspan]:not([rowspan='1']) {
		border-left: 1px solid silver;
	}

	table.data  tbody th[rowspan]:first-child,
	table.index tbody th[rowspan]:first-child,
	table.data  tbody td[rowspan]:first-child,
	table.index tbody td[rowspan]:first-child{
		border-left: 0;
		border-right: 1px solid silver;
	}
*/

/******************************************************************************/
/*                                  Indices                                   */
/******************************************************************************/


/** Table of Contents *********************************************************/

	.toc a {
		/* More spacing; use padding to make it part of the click target. */
		padding: 0.1rem 1px 0;
		/* Larger, more consistently-sized click target */
		display: block;
		/* Switch to using border-bottom for underlines */
		text-decoration: none;
		border-bottom: 1px solid;
		/* Reverse color scheme */
		color: black;
		color: var(--toclink-text);
		border-color: #3980b5;
		border-color: var(--toclink-underline);
	}
	.toc a:visited {
		color: black;
		color: var(--toclink-visited-text);
		border-color: #054572;
		border-color: var(--toclink-visited-underline);
	}
	.toc a:focus,
	.toc a:hover {
		background: rgba(75%, 75%, 75%, .25);
		background: var(--a-hover-bg);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	.toc a:not(:focus):not(:hover) {
		/* Allow colors to cascade through from link styling */
		border-bottom-color: transparent;
	}

	.toc, .toc ol, .toc ul, .toc li {
		list-style: none; /* Numbers must be inlined into source */
		/* because generated content isn't search/selectable and markers can't do multilevel yet */
		margin:  0;
		padding: 0;
	}
	.toc {
		line-height: 1.1em;
	}

	/* ToC not indented until third level, but font style & margins show hierarchy */
	.toc > li			{ font-weight: bold;   }
	.toc > li li		 { font-weight: normal; }
	.toc > li li li	  { font-size:   95%;	}
	.toc > li li li li	{ font-size:   90%;	}
	.toc > li li li li li { font-size:   85%;	}

	/* @supports not (display:grid) { */
		.toc > li			{ margin: 1.5rem 0;	}
		.toc > li li		 { margin: 0.3rem 0;	}
		.toc > li li li	  { margin-left: 2rem;   }

		/* Section numbers in a column of their own */
		.toc .secno {
			float: left;
			width: 4rem;
			white-space: nowrap;
		}
		.toc > li li li li .secno { font-size: 85%; }
		.toc > li li li li li .secno { font-size: 100%; }

		.toc li {
			clear: both;
		}

		:not(li) > .toc			 { margin-left:  5rem; }
		.toc .secno				 { margin-left: -5rem; }
		.toc > li li li .secno	  { margin-left: -7rem; }
		.toc > li li li li .secno	{ margin-left: -9rem; }
		.toc > li li li li li .secno { margin-left: -11rem; }

		/* Tighten up indentation in narrow ToCs */
		@media (max-width: 30em) {
			:not(li) > .toc			 { margin-left:  4rem; }
			.toc .secno				 { margin-left: -4rem; }
			.toc > li li li			 { margin-left:  1rem; }
			.toc > li li li .secno	  { margin-left: -5rem; }
			.toc > li li li li .secno	{ margin-left: -6rem; }
			.toc > li li li li li .secno { margin-left: -7rem; }
		}
		/* Loosen it on wide screens */
		@media screen and (min-width: 78em) {
			body:not(.toc-inline) :not(li) > .toc			 { margin-left:  4rem; }
			body:not(.toc-inline) .toc .secno				 { margin-left: -4rem; }
			body:not(.toc-inline) .toc > li li li			 { margin-left:  1rem; }
			body:not(.toc-inline) .toc > li li li .secno	  { margin-left: -5rem; }
			body:not(.toc-inline) .toc > li li li li .secno	{ margin-left: -6rem; }
			body:not(.toc-inline) .toc > li li li li li .secno { margin-left: -7rem; }
	}
	/* } */

	@supports (display:grid) and (display:contents) {
		/* Use #toc over .toc to override non-@supports rules. */
		#toc {
			display: grid;
			align-content: start;
			grid-template-columns: auto 1fr;
			grid-column-gap: 1rem;
			column-gap: 1rem;
			grid-row-gap: .6rem;
			row-gap: .6rem;
		}
		#toc h2 {
			grid-column: 1 / -1;
			margin-bottom: 0;
		}
		#toc ol,
		#toc li,
		#toc a {
			display: contents;
			/* Switch <a> to subgrid when supported */
		}
		#toc span {
			margin: 0;
		}
		#toc > .toc > li > a > span {
			/* The spans of the top-level list,
			  comprising the first items of each top-level section. */
			margin-top: 1.1rem;
		}
		#toc#toc .secno { /* Ugh, need more specificity to override base.css */
			grid-column: 1;
			width: auto;
			margin-left: 0;
		}
		#toc .content {
			grid-column: 2;
			width: auto;
			margin-right: 1rem;
		}
		#toc .content:hover,
		#toc .content:focus {
			background: rgba(75%, 75%, 75%, .25);
			background: var(--a-hover-bg);
			border-bottom: 3px solid #054572;
			border-bottom: 3px solid var(--toclink-underline);
			margin-bottom: -3px;
		}
		#toc li li li .content {
			margin-left: 1rem;
		}
		#toc li li li li .content {
			margin-left: 2rem;
		}
	}


/** Index *********************************************************************/

	/* Index Lists: Layout */
	ul.index	  { margin-left: 0; columns: 15em; text-indent: 1em hanging; }
	ul.index li	{ margin-left: 0; list-style: none; break-inside: avoid; }
	ul.index li li { margin-left: 1em; }
	ul.index dl	{ margin-top: 0; }
	ul.index dt	{ margin: .2em 0 .2em 20px;}
	ul.index dd	{ margin: .2em 0 .2em 40px;}
	/* Index Lists: Typography */
	ul.index ul,
	ul.index dl { font-size: smaller; }
	@media not print {
		ul.index li a + span {
			white-space: nowrap;
			color: transparent; }
		ul.index li a:hover + span,
		ul.index li a:focus + span {
			color: #707070;
			color: var(--indexinfo-text);
		}
	}

/** Index Tables *****************************************************/
	/* See also the data table styling section, which this effectively subclasses */

	table.index {
		font-size: small;
		border-collapse: collapse;
		border-spacing: 0;
		text-align: left;
		margin: 1em 0;
	}

	table.index td,
	table.index th {
		padding: 0.4em;
	}

	table.index tr:hover td:not([rowspan]),
	table.index tr:hover th:not([rowspan]) {
		color: black;
		color: var(--indextable-hover-text);
		background: #f7f8f9;
		background: var(--indextable-hover-bg);
	}

	/* The link in the first column in the property table (formerly a TD) */
	table.index th:first-child a {
		font-weight: bold;
	}

/** Outdated warning **********************************************************/

.outdated-spec {
	color: black;
	color: var(--outdatedspec-text);
	background-color: rgba(0,0,0,0.5);
	background-color: var(--outdatedspec-bg);
}

.outdated-warning {
	position: fixed;
	bottom: 50%;
	left: 0;
	right: 0;
	margin: 0 auto;
	width: 50%;
	background: maroon;
	background: var(--outdated-bg);
	color: white;
	color: var(--outdated-text);
	border-radius: 1em;
	box-shadow: 0 0 1em red;
	box-shadow: 0 0 1em var(--outdated-shadow);
	padding: 2em;
	text-align: center;
	z-index: 2;
}

.outdated-warning a {
	color: currentcolor;
	background: transparent;
}

.edited-rec-warning {
	background: darkorange;
	background: var(--editedrec-bg);
	box-shadow: 0 0 1em;
}

.outdated-warning button {
	color: var(--outdated-text);
	border-radius: 1em;
	box-shadow: 0 0 1em red;
	box-shadow: 0 0 1em var(--outdated-shadow);
	padding: 2em;
	text-align: center;
	z-index: 2;
}

.outdated-warning a {
	color: currentcolor;
	background: transparent;
}

.edited-rec-warning {
	background: darkorange;
	background: var(--editedrec-bg);
	box-shadow: 0 0 1em;
}

.outdated-warning button {
	position: absolute;
	top: 0;
	right:0;
	margin: 0;
	border: 0;
	padding: 0.25em 0.5em;
	background: transparent;
	color: white;
	color: var(--outdated-text);
	font:1em sans-serif;
	text-align:center;
}

.outdated-warning span {
	display: block;
}

.outdated-collapsed {
	bottom: 0;
	border-radius: 0;
	width: 100%;
	padding: 0;
}

/******************************************************************************/
/*                                    Print                                   */
/******************************************************************************/

	@media print {
		/* Pages have their own margins. */
		html {
			margin: 0;
		}
		/* Serif for print. */
		body {
			font-family: serif;
		}

		.outdated-warning {
			position: absolute;
			border-style: solid;
			border-color: red;
		}

		.outdated-warning input {
			display: none;
		}
	}
	@page {
		margin: 1.5cm 1.1cm;
	}



/******************************************************************************/
/*                             Overflow Control                               */
/******************************************************************************/

	.figure .caption, .sidefigure .caption, figcaption {
		/* in case figure is overlarge, limit caption to 50em */
		max-width: 50rem;
		margin-left: auto;
		margin-right: auto;
	}
	.overlarge {
		/* Magic to create good item positioning:
		  "content column" is 50ems wide at max; less on smaller screens.
		  Extra space (after ToC + content) is empty on the right.

		  1. When item < content column, centers item in column.
		  2. When content < item < available, left-aligns.
		  3. When item > available, fills available + scroll bar.
		*/
		display: grid;
		grid-template-columns: minmax(0, 50em);
	}
	.overlarge > table {
		/* limit preferred width of table */
		max-width: 50em;
		margin-left: auto;
		margin-right: auto;
	}

	@media (min-width: 55em) {
		.overlarge {
			margin-right: calc(13px + 26.5rem - 50vw);
			max-width: none;
		}
	}
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) .overlarge {
			/* 30.5em body padding 50em content area */
			margin-right: calc(40em - 50vw) !important;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) .overlarge {
			/* 4em html margin 30.5em body padding 50em content area */
			margin-right: calc(84.5em - 100vw) !important;
		}
	}

	@media not print {
		.overlarge {
			overflow-x: auto;
			/* See Lea Verou's explanation background-attachment:
			* http://lea.verou.me/2012/04/background-attachment-local/
			*
			background: top left  / 4em 100% linear-gradient(to right,  #ffffff, rgba(255, 255, 255, 0)) local,
						top right / 4em 100% linear-gradient(to left, #ffffff, rgba(255, 255, 255, 0)) local,
						top left  / 1em 100% linear-gradient(to right,  #c3c3c5, rgba(195, 195, 197, 0)) scroll,
						top right / 1em 100% linear-gradient(to left, #c3c3c5, rgba(195, 195, 197, 0)) scroll,
						white;
			background-repeat: no-repeat;
			*/
		}
	}
</style>
<style>
    table, th, td {
      border: 1px solid black;
      border-collapse: collapse;
      vertical-align: top;
    }
    th, td {
      border-left: none;
      border-right: none;
      padding: 0px 10px;
    }
    th {
      text-align: center;
    }

    del { background: #fcc; color: #000; text-decoration: line-through; }
    ins { background: #cfc; color: #000; }
    blockquote .highlight:not(.idl) { background: initial; margin: initial; padding: 0.5em }
    blockquote ul { background: inherit; }
    blockquote code.highlight:not(.idl) { padding: initial; }
    blockquote c-[a] { color: inherit; } /* Keyword.Declaration */
    blockquote c-[b] { color: inherit; } /* Keyword.Type */
    blockquote c-[c] { color: inherit; } /* Comment */
    blockquote c-[d] { color: inherit; } /* Comment.Multiline */
    blockquote c-[e] { color: inherit; } /* Name.Attribute */
    blockquote c-[f] { color: inherit; } /* Name.Tag */
    blockquote c-[g] { color: inherit; } /* Name.Variable */
    blockquote c-[k] { color: inherit; } /* Keyword */
    blockquote c-[l] { color: inherit; } /* Literal */
    blockquote c-[m] { color: inherit; } /* Literal.Number */
    blockquote c-[n] { color: inherit; } /* Name */
    blockquote c-[o] { color: inherit; } /* Operator */
    blockquote c-[p] { color: inherit; } /* Punctuation */
    blockquote c-[s] { color: inherit; } /* Literal.String */
    blockquote c-[t] { color: inherit; } /* Literal.String.Single */
    blockquote c-[u] { color: inherit; } /* Literal.String.Double */
    blockquote c-[cp] { color: inherit; } /* Comment.Preproc */
    blockquote c-[c1] { color: inherit; } /* Comment.Single */
    blockquote c-[cs] { color: inherit; } /* Comment.Special */
    blockquote c-[kc] { color: inherit; } /* Keyword.Constant */
    blockquote c-[kn] { color: inherit; } /* Keyword.Namespace */
    blockquote c-[kp] { color: inherit; } /* Keyword.Pseudo */
    blockquote c-[kr] { color: inherit; } /* Keyword.Reserved */
    blockquote c-[ld] { color: inherit; } /* Literal.Date */
    blockquote c-[nc] { color: inherit; } /* Name.Class */
    blockquote c-[no] { color: inherit; } /* Name.Constant */
    blockquote c-[nd] { color: inherit; } /* Name.Decorator */
    blockquote c-[ni] { color: inherit; } /* Name.Entity */
    blockquote c-[ne] { color: inherit; } /* Name.Exception */
    blockquote c-[nf] { color: inherit; } /* Name.Function */
    blockquote c-[nl] { color: inherit; } /* Name.Label */
    blockquote c-[nn] { color: inherit; } /* Name.Namespace */
    blockquote c-[py] { color: inherit; } /* Name.Property */
    blockquote c-[ow] { color: inherit; } /* Operator.Word */
    blockquote c-[mb] { color: inherit; } /* Literal.Number.Bin */
    blockquote c-[mf] { color: inherit; } /* Literal.Number.Float */
    blockquote c-[mh] { color: inherit; } /* Literal.Number.Hex */
    blockquote c-[mi] { color: inherit; } /* Literal.Number.Integer */
    blockquote c-[mo] { color: inherit; } /* Literal.Number.Oct */
    blockquote c-[sb] { color: inherit; } /* Literal.String.Backtick */
    blockquote c-[sc] { color: inherit; } /* Literal.String.Char */
    blockquote c-[sd] { color: inherit; } /* Literal.String.Doc */
    blockquote c-[se] { color: inherit; } /* Literal.String.Escape */
    blockquote c-[sh] { color: inherit; } /* Literal.String.Heredoc */
    blockquote c-[si] { color: inherit; } /* Literal.String.Interpol */
    blockquote c-[sx] { color: inherit; } /* Literal.String.Other */
    blockquote c-[sr] { color: inherit; } /* Literal.String.Regex */
    blockquote c-[ss] { color: inherit; } /* Literal.String.Symbol */
    blockquote c-[vc] { color: inherit; } /* Name.Variable.Class */
    blockquote c-[vg] { color: inherit; } /* Name.Variable.Global */
    blockquote c-[vi] { color: inherit; } /* Name.Variable.Instance */
    blockquote c-[il] { color: inherit; } /* Literal.Number.Integer.Long */
  </style>
  <meta content="Bikeshed version 44af0bf3e, updated Fri Jul 29 17:05:16 2022 -0700" name="generator">
  <link href="https://isocpp.org/favicon.ico" rel="icon">
  <meta content="66ee11749ee9a78733a7c71adddbcbf2d1033a8d" name="document-revision">
<style>

:root {
	/* Default (light) theme */
	--del-text-color: rgb(255, 25, 25);
	--del-text-decoration-color: rgba(180, 6, 6, 0.5);
	--del-text-background-color: rgba(255, 175, 175, 0.5);
	--ins-text-color: rgb(10, 180, 35);
	--ins-text-decoration-color: rgba(10, 180, 35, 0.5);
	--ins-text-background-color: rgba(175, 250, 190, 0.5);
	--diff-ins-text-color: rgb(0, 238, 255);
	--diff-ins-text-decoration-color: rgba(99, 0, 129, 0.5);
	--diff-ins-text-background-color: rgba(175, 222, 250, 0.5);
	--diff-del-text-color: rgb(225, 148, 255);
	--diff-del-text-decoration-color: rgba(99, 0, 129, 0.5);
	--diff-del-text-background-color: rgba(244, 175, 250, 0.5);
}

/* dark theme */
@media (prefers-color-scheme: dark) {
	:root {
		--del-text-color: rgb(255, 52, 52);
		--del-text-decoration-color: rgba(82, 25, 25, 0.5);
		--del-text-background-color: rgba(82, 25, 25, 0.5);
		--ins-text-color: rgb(140, 255, 140);
		--ins-text-decoration-color: rgba(140, 255, 140, 0.5);
		--ins-text-background-color: rgba(25, 82, 25, 0.5);
		--diff-ins-text-color: rgb(91, 250, 255);
		--diff-ins-text-decoration-color: rgba(91, 250, 255, 0.5);
		--diff-ins-text-background-color: rgba(0, 56, 94, 0.5);
		--diff-del-text-color: rgb(244, 175, 250);
		--diff-del-text-decoration-color: rgba(244, 175, 250, 0.5);
		--diff-del-text-background-color: rgba(152, 0, 199, 0.5);
	}
}

@media print {
	.pagebreak { break-after: always }
}

.tg  {
	border-collapse: collapse;
	border-spacing:0;
}

.tg td{
	padding:10px 10px;
	border-style: solid;
	border-width:1px;
	overflow: hidden;
	word-break: normal;
	border-color: var(--table-border-color, inherit);
}
.tg th{
	font-weight: normal;
	padding: 10px 10px;
	border-style: solid;
	border-width: 1px;
	overflow: hidden;
	word-break: normal;
	border-color: black;
}
.tg .tg-c3ow { 
	border-color: inherit;
	text-align: center;
	vertical-align: top
}

.ins, ins, ins p, ins div, span.ins, span.ins * {
	background-color: var(--ins-text-background-color);
	background: var(--ins-text-background-color);
	color: var(--ins-text-color);
	text-decoration: underline;
	text-decoration-color: var(--ins-text-decoration-color);
}

.diff-ins, diff-ins, diff-ins p, diff-ins div, span.diff-ins, span.diff-ins * {
	background-color: var(--diff-ins-text-background-color);
	background: var(--diff-ins-text-background-color);
	color: var(--diff-ins-text-color);
	text-decoration: underline double;
	text-decoration-color: var(--diff-ins-text-decoration-color);
}

.del, del, del p, del div, span.del, span.del * {
	background-color: var(--del-text-background-color);
	background: var(--del-text-background-color);
	color: var(--del-text-color);
	text-decoration: line-through;
	text-decoration-color: var(--del-text-decoration-color);
}

.diff-del, diff-del, diff-del p, diff-del div, span.diff-del, span.diff-del * {
	background-color: var(--diff-del-text-background-color);
	background: var(--diff-del-text-background-color);
	color: var(--diff-del-text-color);
	text-decoration: line-through double;
	text-decoration-color: var(--diff-del-text-decoration-color);
}

code.c-kw {
	font-weight: bold;
}

math, span.math {
	font-family: serif;
	font-style: italic;
}

ul {
	list-style-type: "— ";
}

.wording-clause {
	counter-reset: wording-paragraph;
}

.wording-clause-header {
	font-size: 115%;
	display: block;
	padding-bottom: 1em;
	clear: both;
}

.wording-clause-number {
	font-weight: bold;
}

.wording-clause-title {
	font-weight: bold;
	margin: 2em;
}

.wording-clause-stable-tag {
	float: right;
}

.wording-clause-section-title {
	font-size: 105%;
	font-weight: bold;
}

.clause-stable-tag {
	float: right;
}

.footnote-ref {
	font-size: 75%;
	vertical-align: super;
}

.footnote {
	font-size: 75%;
	vertical-align: bottom;
}

div.wording-section {
	counter-reset: wording-paragraph;
}

div.wording-numbered, div.wording-newnumbered {
	margin-left: 2.5em;
	margin-top: 1em;
	margin-bottom: 1em;
}

div.wording-numbered:before, div.wording-newnumbered:before {
	position: absolute;
	margin-left: -2.5em;
	display: block;
}

div.wording-numbered:before {
	content: counter(wording-paragraph);
	counter-increment: wording-paragraph;
	font-size: smaller;
}

div.wording-newnumbered:before {
	content: counter(wording-paragraph)"✨";
	counter-increment: wording-paragraph;
	font-size: smaller;
}

div.wording-numbered-list ul, div.wording-newnumbered ul {
	counter-reset: wording-list-item;
}

div.wording-numbered-list li, div.wording-newnumbered li {
	margin-left: 4em;
}

div.wording-numbered-list li:before, div.wording-newnumbered li:before {
	position: absolute;
	margin-left: -4em;
	display: block;
}

div.wording-numbered-list li:before {
	font-size: smaller;
	content: "(" counter(wording-paragraph) "." counter(wording-list-item) ")";
	counter-increment: wording-list-item;
}

div.wording-newnumbered-list li:before {
	content: "(✨" counter(wording-paragraph) "." counter(wording-list-item) ")";
	counter-increment: wording-list-item;
}

div.wording-numbered-0 {
	counter-reset: wording-paragraph -1;
}

div.wording-numbered-1 {
	counter-reset: wording-paragraph 0;
}

div.wording-numbered-2 {
	counter-reset: wording-paragraph 1;
}

div.wording-numbered-3 {
	counter-reset: wording-paragraph 2;
}

div.wording-numbered-4 {
	counter-reset: wording-paragraph 3;
}

div.wording-numbered-5 {
	counter-reset: wording-paragraph 4;
}

div.wording-numbered-6 {
	counter-reset: wording-paragraph 5;
}

div.wording-numbered-7 {
	counter-reset: wording-paragraph 6;
}

div.wording-numbered-8 {
	counter-reset: wording-paragraph 7;
}

div.wording-numbered-9 {
	counter-reset: wording-paragraph 8;
}

div.wording-numbered-10 {
	counter-reset: wording-paragraph 9;
}

div.wording-numbered-11 {
	counter-reset: wording-paragraph 10;
}

div.wording-numbered-12 {
	counter-reset: wording-paragraph 11;
}

div.wording-numbered-13 {
	counter-reset: wording-paragraph 12;
}

div.wording-numbered-14 {
	counter-reset: wording-paragraph 13;
}

div.wording-numbered-15 {
	counter-reset: wording-paragraph 14;
}

div.wording-numbered-16 {
	counter-reset: wording-paragraph 15;
}

div.wording-numbered-17 {
	counter-reset: wording-paragraph 16;
}

div.wording-numbered-18 {
	counter-reset: wording-paragraph 17;
}

div.wording-numbered-19 {
	counter-reset: wording-paragraph 18;
}

div.wording-numbered-20 {
	counter-reset: wording-paragraph 19;
}
</style>
<style>
@media (prefers-color-scheme: dark) {
	:root {
		--bg-color: rgba(0, 0, 0, 0);
	}

	ins { background: rgba(0, 20, 0); color: rgba(115, 255, 110); }
	del { background: rgba(20, 0, 0); color: rgb(255, 124, 124); text-decoration: line-through; }
	recent-ins { background: rgba(0, 20, 0); color: rgba(80, 80, 255); }
	recent-del { background: rgba(20, 0, 0); color: rgb(255, 156, 56); text-decoration: line-through; }
	blockquote .highlight:not(.idl) { padding: 0.5em }
	blockquote ins .highlight:not(.idl) { background: rgba( 0, 20, 0); }
	blockquote del .highlight:not(.idl) { background: rgba(20,  0, 0); }
	blockquote code.highlight:not(.idl) { background: inherit; padding: initial; }

	c-[a] { color: #e783b4 } /* Keyword.Declaration */
	c-[b] { color: #e783b4 } /* Keyword.Type */
	c-[c] { color: #6ad4cc } /* Comment */
	c-[d] { color: #6ad4cc } /* Comment.Multiline */
	c-[e] { color: #92cbf5 } /* Name.Attribute */
	c-[f] { color: #b58900 } /* Name.Tag */
	c-[g] { color: #cb4b16 } /* Name.Variable */
	c-[k] { color: #e783b4 } /* Keyword */
	c-[l] { color: #a2b1b6 } /* Literal */
	c-[m] { color: #a2b1b6 } /* Literal.Number */
	c-[n] { color: #92cbf5 } /* Name */
	c-[o] { color: #a2b1b6 } /* Operator */
	c-[p] { color: #a2b1b6 } /* Punctuation */
	c-[s] { color: #a0a3e5 } /* Literal.String */
	c-[t] { color: #a0a3e5 } /* Literal.String.Single */
	c-[u] { color: #a0a3e5 } /* Literal.String.Double */
	c-[ch] { color: #6ad4cc } /* Comment.Hashbang */
	c-[cp] { color: #6ad4cc } /* Comment.Preproc */
	c-[cpf] { color: #6ad4cc } /* Comment.PreprocFile */
	c-[c1] { color: #6ad4cc } /* Comment.Single */
	c-[cs] { color: #6ad4cc } /* Comment.Special */
	c-[kc] { color: #e783b4 } /* Keyword.Constant */
	c-[kn] { color: #e783b4 } /* Keyword.Namespace */
	c-[kp] { color: #e783b4 } /* Keyword.Pseudo */
	c-[kr] { color: #e783b4 } /* Keyword.Reserved */
	c-[ld] { color: #a2b1b6 } /* Literal.Date */
	c-[nc] { color: #92cbf5 } /* Name.Class */
	c-[no] { color: #92cbf5 } /* Name.Constant */
	c-[nd] { color: #92cbf5 } /* Name.Decorator */
	c-[ni] { color: #92cbf5 } /* Name.Entity */
	c-[ne] { color: #92cbf5 } /* Name.Exception */
	c-[nf] { color: #92cbf5 } /* Name.Function */
	c-[nl] { color: #92cbf5 } /* Name.Label */
	c-[nn] { color: #92cbf5 } /* Name.Namespace */
	c-[py] { color: #92cbf5 } /* Name.Property */
	c-[ow] { color: #a2b1b6 } /* Operator.Word */
	c-[mb] { color: #a2b1b6 } /* Literal.Number.Bin */
	c-[mf] { color: #a2b1b6 } /* Literal.Number.Float */
	c-[mh] { color: #a2b1b6 } /* Literal.Number.Hex */
	c-[mi] { color: #a2b1b6 } /* Literal.Number.Integer */
	c-[mo] { color: #a2b1b6 } /* Literal.Number.Oct */
	c-[sa] { color: #a0a3e5 } /* Literal.String.Affix */
	c-[sb] { color: #a0a3e5 } /* Literal.String.Backtick */
	c-[sc] { color: #a0a3e5 } /* Literal.String.Char */
	c-[dl] { color: #a0a3e5 } /* Literal.String.Delimiter */
	c-[sd] { color: #a0a3e5 } /* Literal.String.Doc */
	c-[se] { color: #a0a3e5 } /* Literal.String.Escape */
	c-[sh] { color: #a0a3e5 } /* Literal.String.Heredoc */
	c-[si] { color: #a0a3e5 } /* Literal.String.Interpol */
	c-[sx] { color: #a0a3e5 } /* Literal.String.Other */
	c-[sr] { color: #a0a3e5 } /* Literal.String.Regex */
	c-[ss] { color: #a0a3e5 } /* Literal.String.Symbol */
	c-[fm] { color: #92cbf5 } /* Name.Function.Magic */
	c-[vc] { color: #cb4b16 } /* Name.Variable.Class */
	c-[vg] { color: #cb4b16 } /* Name.Variable.Global */
	c-[vi] { color: #cb4b16 } /* Name.Variable.Instance */
	c-[vm] { color: #cb4b16 } /* Name.Variable.Magic */
	c-[il] { color: #a2b1b6 } /* Literal.Number.Integer.Long */

	blockquote c-[b] { color: #e783b4 } /* Keyword.Type */
	blockquote c-[a] { color: #e783b4 } /* Keyword.Declaration */
	blockquote c-[c] { color: #6ad4cc } /* Comment */
	blockquote c-[d] { color: #6ad4cc } /* Comment.Multiline */
	blockquote c-[e] { color: #92cbf5 } /* Name.Attribute */
	blockquote c-[f] { color: #b58900 } /* Name.Tag */
	blockquote c-[g] { color: #cb4b16 } /* Name.Variable */
	blockquote c-[k] { color: #e783b4 } /* Keyword */
	blockquote c-[l] { color: #a2b1b6 } /* Literal */
	blockquote c-[m] { color: #a2b1b6 } /* Literal.Number */
	blockquote c-[n] { color: #92cbf5 } /* Name */
	blockquote c-[o] { color: #a2b1b6 } /* Operator */
	blockquote c-[p] { color: #a2b1b6 } /* Punctuation */
	blockquote c-[s] { color: #a0a3e5 } /* Literal.String */
	blockquote c-[t] { color: #a0a3e5 } /* Literal.String.Single */
	blockquote c-[u] { color: #a0a3e5 } /* Literal.String.Double */
	blockquote c-[ch] { color: #6ad4cc } /* Comment.Hashbang */
	blockquote c-[cp] { color: #6ad4cc } /* Comment.Preproc */
	blockquote c-[cpf] { color: #6ad4cc } /* Comment.PreprocFile */
	blockquote c-[c1] { color: #6ad4cc } /* Comment.Single */
	blockquote c-[cs] { color: #6ad4cc } /* Comment.Special */
	blockquote c-[kc] { color: #e783b4 } /* Keyword.Constant */
	blockquote c-[kn] { color: #e783b4 } /* Keyword.Namespace */
	blockquote c-[kp] { color: #e783b4 } /* Keyword.Pseudo */
	blockquote c-[kr] { color: #e783b4 } /* Keyword.Reserved */
	blockquote c-[ld] { color: #a2b1b6 } /* Literal.Date */
	blockquote c-[nc] { color: #92cbf5 } /* Name.Class */
	blockquote c-[no] { color: #92cbf5 } /* Name.Constant */
	blockquote c-[nd] { color: #92cbf5 } /* Name.Decorator */
	blockquote c-[ni] { color: #92cbf5 } /* Name.Entity */
	blockquote c-[ne] { color: #92cbf5 } /* Name.Exception */
	blockquote c-[nf] { color: #92cbf5 } /* Name.Function */
	blockquote c-[nl] { color: #92cbf5 } /* Name.Label */
	blockquote c-[nn] { color: #92cbf5 } /* Name.Namespace */
	blockquote c-[py] { color: #92cbf5 } /* Name.Property */
	blockquote c-[ow] { color: #a2b1b6 } /* Operator.Word */
	blockquote c-[mb] { color: #a2b1b6 } /* Literal.Number.Bin */
	blockquote c-[mf] { color: #a2b1b6 } /* Literal.Number.Float */
	blockquote c-[mh] { color: #a2b1b6 } /* Literal.Number.Hex */
	blockquote c-[mi] { color: #a2b1b6 } /* Literal.Number.Integer */
	blockquote c-[mo] { color: #a2b1b6 } /* Literal.Number.Oct */
	blockquote c-[sa] { color: #a0a3e5 } /* Literal.String.Affix */
	blockquote c-[sb] { color: #a0a3e5 } /* Literal.String.Backtick */
	blockquote c-[sc] { color: #a0a3e5 } /* Literal.String.Char */
	blockquote c-[dl] { color: #a0a3e5 } /* Literal.String.Delimiter */
	blockquote c-[sd] { color: #a0a3e5 } /* Literal.String.Doc */
	blockquote c-[se] { color: #a0a3e5 } /* Literal.String.Escape */
	blockquote c-[sh] { color: #a0a3e5 } /* Literal.String.Heredoc */
	blockquote c-[si] { color: #a0a3e5 } /* Literal.String.Interpol */
	blockquote c-[sx] { color: #a0a3e5 } /* Literal.String.Other */
	blockquote c-[sr] { color: #a0a3e5 } /* Literal.String.Regex */
	blockquote c-[ss] { color: #a0a3e5 } /* Literal.String.Symbol */
	blockquote c-[fm] { color: #92cbf5 } /* Name.Function.Magic */
	blockquote c-[vc] { color: #cb4b16 } /* Name.Variable.Class */
	blockquote c-[vg] { color: #cb4b16 } /* Name.Variable.Global */
	blockquote c-[vi] { color: #cb4b16 } /* Name.Variable.Instance */
	blockquote c-[vm] { color: #cb4b16 } /* Name.Variable.Magic */
	blockquote c-[il] { color: #a2b1b6 } /* Literal.Number.Integer.Long */
}

@media (prefers-color-scheme: light) {
	:root {
		--bg-color: rgba(255, 255, 255, 0);
	}
	ins { background: rgba(200, 255, 200); color: rgba(0, 20, 0); }
	del { background: rgba(255, 200, 200); color: rgb(20, 0, 0); text-decoration: line-through; }
	blockquote .highlight:not(.idl) { padding: 0.5em }
	blockquote ins .highlight:not(.idl) { background: rgba(200, 255, 200); }
	blockquote del .highlight:not(.idl) { background: rgba(255, 200, 200); }
	blockquote code.highlight:not(.idl) { background: inherit; padding: initial; }
}
</style>
<style>/* style-autolinks */

.css.css, .property.property, .descriptor.descriptor {
    color: var(--a-normal-text);
    font-size: inherit;
    font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
    content: "‘";
}
.css::after, .property::after, .descriptor::after {
    content: "’";
}
.property, .descriptor {
    /* Don't wrap property and descriptor names */
    white-space: nowrap;
}
.type { /* CSS value <type> */
    font-style: italic;
}
pre .property::before, pre .property::after {
    content: "";
}
[data-link-type="property"]::before,
[data-link-type="propdesc"]::before,
[data-link-type="descriptor"]::before,
[data-link-type="value"]::before,
[data-link-type="function"]::before,
[data-link-type="at-rule"]::before,
[data-link-type="selector"]::before,
[data-link-type="maybe"]::before {
    content: "‘";
}
[data-link-type="property"]::after,
[data-link-type="propdesc"]::after,
[data-link-type="descriptor"]::after,
[data-link-type="value"]::after,
[data-link-type="function"]::after,
[data-link-type="at-rule"]::after,
[data-link-type="selector"]::after,
[data-link-type="maybe"]::after {
    content: "’";
}

[data-link-type].production::before,
[data-link-type].production::after,
.prod [data-link-type]::before,
.prod [data-link-type]::after {
    content: "";
}

[data-link-type=element],
[data-link-type=element-attr] {
    font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace;
    font-size: .9em;
}
[data-link-type=element]::before { content: "<" }
[data-link-type=element]::after  { content: ">" }

[data-link-type=biblio] {
    white-space: pre;
}</style>
<style>/* style-colors */

/* Any --*-text not paired with a --*-bg is assumed to have a transparent bg */
:root {
    color-scheme: light dark;

    --text: black;
    --bg: white;

    --unofficial-watermark: url(https://www.w3.org/StyleSheets/TR/2016/logos/UD-watermark);

    --logo-bg: #1a5e9a;
    --logo-active-bg: #c00;
    --logo-text: white;

    --tocnav-normal-text: #707070;
    --tocnav-normal-bg: var(--bg);
    --tocnav-hover-text: var(--tocnav-normal-text);
    --tocnav-hover-bg: #f8f8f8;
    --tocnav-active-text: #c00;
    --tocnav-active-bg: var(--tocnav-normal-bg);

    --tocsidebar-text: var(--text);
    --tocsidebar-bg: #f7f8f9;
    --tocsidebar-shadow: rgba(0,0,0,.1);
    --tocsidebar-heading-text: hsla(203,20%,40%,.7);

    --toclink-text: var(--text);
    --toclink-underline: #3980b5;
    --toclink-visited-text: var(--toclink-text);
    --toclink-visited-underline: #054572;

    --heading-text: #005a9c;

    --hr-text: var(--text);

    --algo-border: #def;

    --del-text: red;
    --del-bg: transparent;
    --ins-text: #080;
    --ins-bg: transparent;

    --a-normal-text: #034575;
    --a-normal-underline: #bbb;
    --a-visited-text: var(--a-normal-text);
    --a-visited-underline: #707070;
    --a-hover-bg: rgba(75%, 75%, 75%, .25);
    --a-active-text: #c00;
    --a-active-underline: #c00;

    --blockquote-border: silver;
    --blockquote-bg: transparent;
    --blockquote-text: currentcolor;

    --issue-border: #e05252;
    --issue-bg: #fbe9e9;
    --issue-text: var(--text);
    --issueheading-text: #831616;

    --example-border: #e0cb52;
    --example-bg: #fcfaee;
    --example-text: var(--text);
    --exampleheading-text: #574b0f;

    --note-border: #52e052;
    --note-bg: #e9fbe9;
    --note-text: var(--text);
    --noteheading-text: hsl(120, 70%, 30%);
    --notesummary-underline: silver;

    --assertion-border: #aaa;
    --assertion-bg: #eee;
    --assertion-text: black;

    --advisement-border: orange;
    --advisement-bg: #fec;
    --advisement-text: var(--text);
    --advisementheading-text: #b35f00;

    --warning-border: red;
    --warning-bg: hsla(40,100%,50%,0.95);
    --warning-text: var(--text);

    --amendment-border: #330099;
    --amendment-bg: #F5F0FF;
    --amendment-text: var(--text);
    --amendmentheading-text: #220066;

    --def-border: #8ccbf2;
    --def-bg: #def;
    --def-text: var(--text);
    --defrow-border: #bbd7e9;

    --datacell-border: silver;

    --indexinfo-text: #707070;

    --indextable-hover-text: black;
    --indextable-hover-bg: #f7f8f9;

    --outdatedspec-bg: rgba(0, 0, 0, .5);
    --outdatedspec-text: black;
    --outdated-bg: maroon;
    --outdated-text: white;
    --outdated-shadow: red;

    --editedrec-bg: darkorange;
}</style>
<style>/* style-counters */

body {
    counter-reset: example figure issue;
}
.issue {
    counter-increment: issue;
}
.issue:not(.no-marker)::before {
    content: "Issue " counter(issue);
}

.example {
    counter-increment: example;
}
.example:not(.no-marker)::before {
    content: "Example " counter(example);
}
.invalid.example:not(.no-marker)::before,
.illegal.example:not(.no-marker)::before {
    content: "Invalid Example" counter(example);
}

figcaption {
    counter-increment: figure;
}
figcaption:not(.no-marker)::before {
    content: "Figure " counter(figure) " ";
}</style>
<style>/* style-issues */

a[href].issue-return {
    float: right;
    float: inline-end;
    color: var(--issueheading-text);
    font-weight: bold;
    text-decoration: none;
}
</style>
<style>/* style-md-lists */

/* This is a weird hack for me not yet following the commonmark spec
   regarding paragraph and lists. */
[data-md] > :first-child {
    margin-top: 0;
}
[data-md] > :last-child {
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 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">P2537R2<br>Relax <code class="highlight"><c- n>va_start</c-></code> Requirements to Match C</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="profile-and-date"><span class="content">Published Proposal, <time class="dt-updated" datetime="2022-11-09">2022-11-09</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt class="editor">Author:
     <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:phdofthehouse@gmail.com">JeanHeyd Meneide (https://thephd.dev)</a>
     <dt>Audience:
     <dd>LEWG
     <dt>Project:
     <dd>ISO/IEC JTC1/SC22/WG21 14882: Programming Language — C++
     <dt>Target:
     <dd>C++26
     <dt>Latest:
     <dd><a href="https://thephd.dev/_vendor/future_cxx/papers/d2537.html">https://thephd.dev/_vendor/future_cxx/papers/d2537.html</a>
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <hr title="Separator for header">
  </div>
  <div class="p-summary" data-fill-with="abstract">
   <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
   <p>At the WG14 January/February Meeting on February 1st, WG14 voted heavily in favor of allowing <code class="highlight"><c- n>va_start</c-><c- o>/</c-><c- n>arg</c-><c- o>/</c-><c- n>end</c-><c- o>/</c-><c- n>list</c-></code>-style functions to be able to take 0 arguments, alongside removing the requirement of a special "last parameter" being passed to <code class="highlight"><c- n>va_start</c-></code>. C++ has always allowed function declarations and definitions with zero arguments, but intentionally left <code class="highlight"><c- n>va_start</c-></code> un-updated to match C’s existing practice. This paper follows the new direction for C to remove the restrictions from <code class="highlight"><c- n>va_start</c-></code> in C.</p>
  </div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li>
     <a href="#changelog"><span class="secno">1</span> <span class="content">Revision History</span></a>
     <ol class="toc">
      <li><a href="#changelog-r2"><span class="secno">1.1</span> <span class="content">Revision 2 - November 10th, 2022</span></a>
      <li><a href="#changelog-r1"><span class="secno">1.2</span> <span class="content">Revision 1 - July 22nd, 2022</span></a>
      <li><a href="#changelog-r0"><span class="secno">1.3</span> <span class="content">Revision 0 - February 15th, 2022</span></a>
     </ol>
    <li>
     <a href="#intro"><span class="secno">2</span> <span class="content">Introduction and Motivation</span></a>
     <ol class="toc">
      <li>
       <a href="#intro-solution"><span class="secno">2.1</span> <span class="content">The Solution</span></a>
       <ol class="toc">
        <li><a href="#intro-solution-abi"><span class="secno">2.1.1</span> <span class="content">What if the ABI is different?</span></a>
        <li><a href="#intro-solution-decl.vs.defn"><span class="secno">2.1.2</span> <span class="content">Allow Declaration, not but don’t allow Definitions?</span></a>
       </ol>
     </ol>
    <li>
     <a href="#wording"><span class="secno">3</span> <span class="content">Specification</span></a>
     <ol class="toc">
      <li>
       <a href="#wording-library"><span class="secno">3.1</span> <span class="content">Library Wording</span></a>
       <ol class="toc">
        <li><a href="#wording-library.cstdarg.syn"><span class="secno">3.1.1</span> <span class="content">Modify Header <cstdarg> Synopsis [<span>cstdarg.syn</span>] To Delete All But First Sentence</cstdarg></span></a>
       </ol>
     </ol>
    <li>
     <a href="#appenxdix"><span class="secno">4</span> <span class="content">Appendix</span></a>
     <ol class="toc">
      <li>
       <a href="#appendix-wording"><span class="secno">4.1</span> <span class="content">Old Wording Alternatives</span></a>
       <ol class="toc">
        <li><a href="#appendix-wording-alt1.cstdarg.syn"><span class="secno">4.1.1</span> <span class="content">ALTERNATIVE 1: Modify Header <cstdarg> Synopsis [<span>cstdarg.syn</span>]</cstdarg></span></a>
       </ol>
     </ol>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
     </ol>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="changelog"><span class="secno">1. </span><span class="content">Revision History</span><a class="self-link" href="#changelog"></a></h2>
   <h3 class="heading settled" data-level="1.1" id="changelog-r2"><span class="secno">1.1. </span><span class="content">Revision 2 - November 10th, 2022</span><a class="self-link" href="#changelog-r2"></a></h3>
   <ul>
    <li data-md>
     <p>(SUPERSEDED) Propose 2 different specifications in <a href="#appendix-wording-alt1.cstdarg.syn">Alternative 1</a> and <a href="#wording-library.cstdarg.syn">Alternative 2</a> for wording with respect to how C23 does it. Ask CWG and EWG for feedback.</p>
    <li data-md>
     <p>(November 9th, 2022) <a href="#wording-library.cstdarg.syn">Alternative 2</a> was settled on and Alternative 1 was moved to the appendix.</p>
    <li data-md>
     <p>Sent off to LEWG, to obtain approval to get into CWG/LWG.</p>
   </ul>
   <h3 class="heading settled" data-level="1.2" id="changelog-r1"><span class="secno">1.2. </span><span class="content">Revision 1 - July 22nd, 2022</span><a class="self-link" href="#changelog-r1"></a></h3>
   <ul>
    <li data-md>
     <p>Aligned specification with (now accepted) C23 paper for this feature, <a data-link-type="biblio" href="#biblio-n2975">[n2975]</a>, losing the <code class="highlight"><c- n>parmN</c-></code> specification.</p>
   </ul>
   <h3 class="heading settled" data-level="1.3" id="changelog-r0"><span class="secno">1.3. </span><span class="content">Revision 0 - February 15th, 2022</span><a class="self-link" href="#changelog-r0"></a></h3>
   <ul>
    <li data-md>
     <p>SG22 saw this paper on February 11th, 2022 and voted in favor of forwarding it towards WG21 and for WG14. They do not see any compatibility issues, but recommended two things:</p>
     <ul>
      <li data-md>
       <p>Allowing declarations but not definitions in the C paper;</p>
      <li data-md>
       <p>and, talking about ABI changes.</p>
     </ul>
    <li data-md>
     <p>Initial Release! 🎉</p>
   </ul>
   <h2 class="heading settled" data-level="2" id="intro"><span class="secno">2. </span><span class="content">Introduction and Motivation</span><a class="self-link" href="#intro"></a></h2>
   <p>C merged a paper to remove functions without prototypes ("K&amp;R Functions") from C23, closing the chapter on a nearly 40 year old deprecated feature. Unfortunately, K&amp;R declarations served a number of useful purposes that could not be effectively approximated by any other function declaration in C. In C++, old-style K&amp;R functions on both an ABI and an API level could be approximated with a declaration such as <code class="highlight"><c- b>void</c-> <c- nf>f</c-><c- p>(...);</c-></code>. This was impossible in C thanks to the requirement in both the language that there must be at least one parameter before the <code class="highlight"><c- p>...</c-></code>, and that the last parameter must be passed to <code class="highlight"><c- n>va_start</c-></code>. This is bad because many inter-language function calls and similar were enabled in plain, standard C by using K&amp;R declarations and then having the non-C side use assembly or other tricks to appropriately handle both passed-in arguments as well as return values:</p>
<pre class="language-cpp highlight"><c- c1>// Pre-C23 K&amp;R Declaration</c->
<c- b>double</c-> <c- nf>compute_values</c-><c- p>();</c->

<c- b>int</c-> <c- nf>main</c-> <c- p>()</c-> <c- p>{</c->
	<c- c1>// C: allowed usage under K&amp;R rules, removed in C23</c->
	<c- c1>// C++: ill-formed (constraint violation), function takes 0 arguments</c->
	<c- b>double</c-> <c- n>x</c-> <c- o>=</c-> <c- n>compute_values</c-><c- p>(</c-><c- s>"with_pi"</c-><c- p>,</c-> <c- mf>2.4</c-><c- p>,</c-> <c- mf>2.7</c-><c- p>,</c-> true<c- p>);</c->
	<c- k>return</c-> <c- p>(</c-><c- b>int</c-><c- p>)</c-><c- n>x</c-><c- p>;</c->
<c- p>}</c->
</pre>
   <p>The implementation of <code class="highlight"><c- n>compute_values</c-></code> here could be done VIA assembly or with other tricks in other languages, allowing a C codebase to talk to other programming languages and tools efficiently without having to create a dedicated Foreign Function Interface. Unfortunately, the removal of K&amp;R declarations in C has made the above code illegal in standard C, and taken away a fairly valid use case for prototype-less functions.</p>
   <h3 class="heading settled" data-level="2.1" id="intro-solution"><span class="secno">2.1. </span><span class="content">The Solution</span><a class="self-link" href="#intro-solution"></a></h3>
   <p>C is moving to fix this problem by allowing <code class="highlight"><c- b>void</c-> <c- nf>f</c-><c- p>(...);</c-></code> as a valid function declaration, as shown in WG14’s <a data-link-type="biblio" href="#biblio-n2975">[n2975]</a>. This will allow the same level of power as K&amp;R declarations without the problematic no-arguments-but-takes-any-number-of-arguments-actually double-meaning syntax. In order to do this, C is updating the <code class="highlight"><c- n>va_start</c-></code> macro as well as fixing its language rules. C++ does not need to fix any of its language rules:</p>
<pre class="language-cpp highlight"><c- c1>// Valid in C23, always valid C++</c->
<c- b>double</c-> <c- nf>compute_values</c-><c- p>(...);</c->

<c- b>int</c-> <c- nf>main</c-> <c- p>()</c-> <c- p>{</c->
	<c- c1>// C and C++: allowed and portable in both languages</c->
	<c- b>double</c-> <c- n>x</c-> <c- o>=</c-> <c- n>compute_values</c-><c- p>(</c-><c- s>"with_pi"</c-><c- p>,</c-> <c- mf>2.4</c-><c- p>,</c-> <c- mf>2.7</c-><c- p>,</c-> true<c- p>);</c->
	<c- k>return</c-> <c- p>(</c-><c- b>int</c-><c- p>)</c-><c- n>x</c-><c- p>;</c->
<c- p>}</c->
</pre>
   <p>Since C++ includes the <code class="highlight"><c- o>&lt;</c-><c- n>stdarg</c-><c- p>.</c-><c- n>h</c-><c- o>></c-></code> header as part of its library offerings in <code class="highlight"><c- o>&lt;</c-><c- n>cstdarg</c-><c- o>></c-></code>, some adjustments must be made to the contents of the synopsis and wording for <code class="highlight"><c- o>&lt;</c-><c- n>cstdarg</c-><c- o>></c-></code> to match the changes that will be made for C. Additionally, some modifications must be made to the constraints to match the changes C makes. Because this is something that was not previously allowed before, it has no impact on existing implementations and for all major compilers (GCC, MSVC, Clang, and their derivates) they have the necessary built-in compiler magic to produce working library implementations that do not require the first argument to <code class="highlight"><c- n>va_start</c-></code>.</p>
   <p>An example proving that this is possible is publicly available here: <a data-link-type="biblio" href="#biblio-ztdvargs">ztd.vargs (https://ztdvargs.readthedocs.io/en/latest/)</a>. The ABI for variadic arguments versus K&amp;R prototypes is no affected because the C ABI did not allow this declaration before, so there is no existing standard code for C that could rely on this function call. C++ may have an ABI for it, but no standards-compliant code could access any of the function arguments using <code class="highlight"><c- n>va_start</c-></code>/<code class="highlight"><c- n>va_arg</c-></code>/<code class="highlight"><c- n>va_end</c-></code> thanks to the macro’s specification. Therefore, this feature either introduces a new ABI that did not previously exist on the platform at all, or simply utilizes an existing ABI (the example library implementation leverages well-defined existing ABIs in C++ implementations in order to work properly).</p>
   <h4 class="heading settled" data-level="2.1.1" id="intro-solution-abi"><span class="secno">2.1.1. </span><span class="content">What if the ABI is different?</span><a class="self-link" href="#intro-solution-abi"></a></h4>
   <p>There are a handful of C compilers that allow declarations using variable arguments without a first parameter, and some shared C and C++ compiler implementations which also allow it by having <code class="highlight"><c- k>extern</c-> <c- s>"C"</c-></code> functions declared without the first parameter in C++. Therefore, there can be compilers which do not share an ABI for their K&amp;R and their variable argument declarations.</p>
   <p>The solution here is not something that can be specified in the standard. This paper can only recommend that implementations which need more explicit control over the resulting ABI of their K&amp;R functions may need to provide an attribute. like below, when performing the migration:</p>
<pre class="language-cpp highlight"><c- p>[[</c-><c- n>impl</c-><c- o>::</c-><c- n>krdecl</c-><c- p>]]</c-> <c- b>double</c-> <c- n>compute_values</c-><c- p>(...);</c->

<c- b>int</c-> <c- nf>main</c-> <c- p>()</c-> <c- p>{</c->
	<c- c1>// compute_values uses right register and stack allocation convention</c->
	<c- b>double</c-> <c- n>x</c-> <c- o>=</c-> <c- n>compute_values</c-><c- p>(</c-><c- s>"with_pi"</c-><c- p>,</c-> <c- mf>2.4</c-><c- p>,</c-> <c- mf>2.7</c-><c- p>,</c-> true<c- p>);</c->
	<c- k>return</c-> <c- p>(</c-><c- b>int</c-><c- p>)</c-><c- n>x</c-><c- p>;</c->
<c- p>}</c->
</pre>
   <p>This can alleviate much of the trouble of porting, and can still be automated when upgrading to C23. We do not have any means in the standard to provide an <code class="highlight"><c- p>[[</c-><c- n>impl</c-><c- o>::</c-><c- n>krdecl</c-><c- p>]]</c-></code> or similar because ABI, register usage, and similar calling convention work is somewhat outside the scope of the standard.</p>
   <h4 class="heading settled" data-level="2.1.2" id="intro-solution-decl.vs.defn"><span class="secno">2.1.2. </span><span class="content">Allow Declaration, not but don’t allow Definitions?</span><a class="self-link" href="#intro-solution-decl.vs.defn"></a></h4>
   <p>There was discussion about allowing this to change only the ability in C to declare these C functions, and not to define them. This is different from C++ where it is both allowed to be declared and defined with no first parameter. Clang also has an extension that allows these functions to be both declared and defined with C or C++-style name mangling:</p>
<pre class="language-cpp highlight"><c- b>void</c-> <c- nf>func</c-><c- p>(...)</c-> <c- n>__attribute__</c-><c- p>((</c-><c- n>overloadable</c-><c- p>))</c-> <c- p>{</c->

<c- p>}</c->

<c- b>int</c-> <c- nf>main</c-><c- p>()</c-> <c- p>{</c->
  <c- n>func</c-><c- p>(</c-><c- mi>1</c-><c- p>,</c-> <c- mi>2</c-><c- p>,</c-> <c- mi>3</c-><c- p>);</c->
<c- p>}</c->
</pre>
   <p>The original paper in <a data-link-type="biblio" href="#biblio-n2975">[n2975]</a> and this paper posit that it would be too inconsistent to allow declaratins (like C++) but disallow definitions (unlike C++) in C. Therefore, the C paper is going forward with changing <code class="highlight"><c- n>va_start</c-></code> and allowing both declarations and definitions. This paper is also being put in the C++ mailing list to bring C++ up to the same level of compatibility with C, if the WG14 N2975 change is made. If the change is withdrawn than this paper will be removed.</p>
   <h2 class="heading settled" data-level="3" id="wording"><span class="secno">3. </span><span class="content">Specification</span><a class="self-link" href="#wording"></a></h2>
   <p>The specification is relative to the latest C++ Working Draft, <a data-link-type="biblio" href="#biblio-n4901">[n4901]</a>.</p>
   <h3 class="heading settled" data-level="3.1" id="wording-library"><span class="secno">3.1. </span><span class="content">Library Wording</span><a class="self-link" href="#wording-library"></a></h3>
   <h4 class="heading settled" data-level="3.1.1" id="wording-library.cstdarg.syn"><span class="secno">3.1.1. </span><span class="content">Modify Header <cstdarg> Synopsis [<a href="https://eel.is/c++draft//cstdarg.syn">cstdarg.syn</a>] To Delete All But First Sentence</cstdarg></span><a class="self-link" href="#wording-library.cstdarg.syn"></a></h4>
   <blockquote>
    <div class="wording-section">
     <div class="wording-section-header"> <span class="clause-title"><b>17.13.2</b></span> <span><b>Header <code class="highlight"><c- o>&lt;</c-><c- n>cstdarg</c-><c- o>></c-></code> Synopsis</b></span> <span class="stable-tag">[<a href="https://eel.is/c++draft/cstdarg.syn">cstdarg.syn</a>]</span> </div>
     <div>
<pre class="language-cpp highlight"><c- k>namespace</c-> <c- nn>std</c-> <c- p>{</c->
  <c- k>using</c-> <c- b>va_list</c-> <c- o>=</c-> <c- n>see</c-> <c- n>below</c-><c- p>;</c->
<c- p>}</c->

<c- cp>#define va_arg(V, P) see below</c->
<c- cp>#define va_copy(VDST, VSRC) see below</c->
<c- cp>#define va_end(V) see below</c->
</pre>
      <del>
<pre class="language-cpp highlight"><c- cp>#define va_start(V, P) see below</c->
</pre>
      </del>
      <ins>
<pre class="language-cpp highlight"><c- cp>#define va_start(V, ...) see below</c->
</pre>
      </ins>
<pre class="language-cpp highlight"><c- p>}</c->
</pre>
     </div>
     <div class="wording-numbered">
      <p>
       The contents of the header <code class="highlight"><c- o>&lt;</c-><c- n>cstdarg</c-><c- o>></c-></code> are the same as the C standard library header <code class="highlight"><c- o>&lt;</c-><c- n>stdarg</c-><c- p>.</c-><c- n>h</c-><c- o>></c-></code>, with the following changes: in lieu of the default argument promotions specified in ISO C 6.5.2.2, the definition in 7.6.1.3 ([expr.call]) applies.
       <del>
        The restrictions that ISO C places on the second parameter to the <code class="highlight"><c- n>va_</c->­<c- n>start</c-></code> macro in header 
        <stdarg.h> are different in this document. The parameter <code class="highlight"><c- n>parmN</c-></code> is the rightmost parameter in the variable parameter list of the function definition (the one just before the ...). If the parameter <code class="highlight"><c- n>parmN</c-></code> is a pack expansion ([temp.variadic]) or an entity resulting from a lambda capture ([expr.prim.lambda]), the program is ill-formed, no diagnostic required. If the parameter <code class="highlight"><c- n>parmN</c-></code> is of a reference type, or of a type that is not compatible with the type that results when passing an argument for which there is no parameter, the behavior is undefined.</stdarg.h>
       </del>
      </p>
      <p>SEE ALSO: ISO C 7.16.1.1</p>
     </div>
    </div>
   </blockquote>
   <h2 class="heading settled" data-level="4" id="appenxdix"><span class="secno">4. </span><span class="content">Appendix</span><a class="self-link" href="#appenxdix"></a></h2>
   <h3 class="heading settled" data-level="4.1" id="appendix-wording"><span class="secno">4.1. </span><span class="content">Old Wording Alternatives</span><a class="self-link" href="#appendix-wording"></a></h3>
   <p>Previously, this was an old wording alternative that was thrown out as it had no benefit or bearing.</p>
   <h4 class="heading settled" data-level="4.1.1" id="appendix-wording-alt1.cstdarg.syn"><span class="secno">4.1.1. </span><span class="content">ALTERNATIVE 1: Modify Header <cstdarg> Synopsis [<a href="https://eel.is/c++draft//cstdarg.syn">cstdarg.syn</a>]</cstdarg></span><a class="self-link" href="#appendix-wording-alt1.cstdarg.syn"></a></h4>
   <blockquote>
    <div class="wording-section">
     <div class="wording-section-header"> <span class="clause-title"><b>17.13.2</b></span> <span><b>Header <code class="highlight"><c- o>&lt;</c-><c- n>cstdarg</c-><c- o>></c-></code> Synopsis</b></span> <span class="stable-tag">[<a href="https://eel.is/c++draft/cstdarg.syn">cstdarg.syn</a>]</span> </div>
     <div>
<pre class="language-cpp highlight"><c- k>namespace</c-> <c- nn>std</c-> <c- p>{</c->
  <c- k>using</c-> <c- b>va_list</c-> <c- o>=</c-> <c- n>see</c-> <c- n>below</c-><c- p>;</c->
<c- p>}</c->

<c- cp>#define va_arg(V, P) see below</c->
<c- cp>#define va_copy(VDST, VSRC) see below</c->
<c- cp>#define va_end(V) see below</c->
</pre>
      <del>
<pre class="language-cpp highlight"><c- cp>#define va_start(V, P) see below</c->
</pre>
      </del>
      <ins>
<pre class="language-cpp highlight"><c- cp>#define va_start(V, ...) see below</c->
</pre>
      </ins>
<pre class="language-cpp highlight"><c- p>}</c->
</pre>
     </div>
     <div class="wording-numbered">
      <p>
       The contents of the header <code class="highlight"><c- o>&lt;</c-><c- n>cstdarg</c-><c- o>></c-></code> are the same as the C standard library header <code class="highlight"><c- o>&lt;</c-><c- n>stdarg</c-><c- p>.</c-><c- n>h</c-><c- o>></c-></code>, with the following changes: The restrictions that ISO C places on the second parameter
       <ins>, if provided,</ins>
        to the <code class="highlight"><c- n>va_</c->­<c- n>start</c-></code> macro in header <code class="highlight"><c- o>&lt;</c-><c- n>stdarg</c-><c- p>.</c-><c- n>h</c-><c- o>></c-></code> are different in this document. The 
       <ins>second parameter to <code class="highlight"><c- n>va_start</c-></code>, if provided,</ins>
       <del>parameter <code class="highlight"><c- n>parmN</c-></code></del>
        is the rightmost parameter in the variable parameter list of the function definition (the one just before the <code class="highlight"><c- p>...</c-></code>)<sup>207</sup>. If the 
       <ins>provided </ins>
       parameter 
       <del><code class="highlight"><c- n>parmN</c-></code></del>
        is a pack expansion ([temp.variadic]) or an entity resulting from a lambda capture ([expr.prim.lambda]), the program is ill-formed, no diagnostic required. If the 
       <ins>provided </ins>
       parameter 
       <del><code class="highlight"><c- n>parmN</c-></code></del>
        is of a reference type, or of a type that is not compatible with the type that results when passing an argument for which there is no parameter, the behavior is undefined.
      </p>
      <p>SEE ALSO: ISO C 7.16.1.1</p>
     </div>
    </div>
   </blockquote>
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  <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
  <h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
  <dl>
   <dt id="biblio-n2975">[N2975]
   <dd>Alex Gilding; JeanHeyd Meneide. <a href="http://open-std.org/JTC1/SC22/WG14/www/docs/n2975.pdf"><cite>Relax requirements for variadic parameter lists</cite></a>. April 15th, 2022. URL: <a href="http://open-std.org/JTC1/SC22/WG14/www/docs/n2975.pdf">http://open-std.org/JTC1/SC22/WG14/www/docs/n2975.pdf</a>
   <dt id="biblio-n4901">[N4901]
   <dd>Thomas Köppe. <a href="https://wg21.link/n4901"><cite>Working Draft, Standard for Programming Language C++</cite></a>. 22 October 2021. URL: <a href="https://wg21.link/n4901">https://wg21.link/n4901</a>
   <dt id="biblio-ztdvargs">[ZTD.VARGS]
   <dd>JeanHeyd Meneide; Shepherd's Oasis, LLC. <a href="https://ztdvargs.readthedocs.io/en/latest/"><cite>ztd.vargs</cite></a>. November 22nd, 2021. URL: <a href="https://ztdvargs.readthedocs.io/en/latest/">https://ztdvargs.readthedocs.io/en/latest/</a>
  </dl>