https://www.w3.org/WAI/ARIA/apg/practices/names-and-descriptions/ says:

[mandoc.git] / roff.7

diff --git a/roff.7 b/roff.7
index 6ebde4fff15ce35f3a665c459b144c4a75424a86..2d58efd6cec3c9ef67e9e515102698eddb7935b9 100644 (file)
--- a/roff.7
+++ b/roff.7
@@ -1,4 +1,4 @@
-.\" $Id: roff.7,v 1.118 2022/05/30 23:03:47 schwarze Exp $
+.\" $Id: roff.7,v 1.120 2022/05/31 20:23:05 schwarze Exp $
 .\"
 .\" Copyright (c) 2010-2019, 2022 Ingo Schwarze <schwarze@openbsd.org>
 .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
@@ -15,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: May 30 2022 $
+.Dd $Mdocdate: May 31 2022 $
 .Dt ROFF 7
 .Os
 .Sh NAME
@@ -2021,8 +2021,23 @@ End conditional input; see
 Paddable non-breaking space character.
 .It Ic \e0
 Digit width space character.
-.It Ic \eA\(aq Ns Ar string Ns Ic \(aq
-Anchor definition; ignored by
+.It Ic \eA\(aq Ns Ar name Ns Ic \(aq
+Interpolate
+.Sq 1
+if
+.Ar name
+is a syntactically valid identifier that can be used
+as a name for a macro or user-defined string, or
+.Sq 0
+otherwise.
+This is a thoroughly non-portable groff extension.
+Heirloom troff uses the same escape sequence with the same syntax
+for a completely different purpose,
+defining a hyperlink target position, also called an
+.Dq anchor ,
+with the given
+.Ar name .
+The Heirloom semantics is not supported by
 .Xr mandoc 1 .
 .It Ic \ea
 Leader character; ignored by
@@ -2085,7 +2100,8 @@ defaults to
 .Ic \efP .
 .It Ic \eg[ Ns Ar name Ns Ic \&]
 Interpolate the format of a number register; ignored by
-.Xr mandoc 1 .
+.Xr mandoc 1 ,
+which interpolates an empty string instead.
 For short names, there are variants
 .Ic \eg Ns Ar c
 and