gbranden pushed a commit to branch master
in repository groff.
commit ecae8c838bf806d4091311fda363a34bf3060831
Author: G. Branden Robinson <[email protected]>
AuthorDate: Tue Apr 21 14:01:49 2026 -0500
[troff]: Style-warn on nilpotent `\{` and `\}`.
Throw warning in category "style" when nilpotent brace escape sequences
are encountered.
* src/roff/troff/input.cpp (read_character_in_copy_mode): Do it.
* doc/groff.texi.in (Conditional Blocks, Warnings):
* man/groff.7.man (Conditional blocks):
* src/roff/troff/troff.1.man (Warnings): Document new warning
circumstance.
---
ChangeLog | 12 ++++++++++++
doc/groff.texi.in | 12 ++++++++++--
man/groff.7.man | 13 +++++++++++--
src/roff/troff/input.cpp | 2 ++
src/roff/troff/troff.1.man | 1 +
5 files changed, 36 insertions(+), 4 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index f6aae51f4..17c08f2ce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2026-04-21 G. Branden Robinson <[email protected]>
+
+ [troff]: Throw warning in category "style" when nilpotent brace
+ escape sequences are encountered.
+
+ * src/roff/troff/input.cpp (read_character_in_copy_mode): Do it.
+
+ * doc/groff.texi.in (Conditional Blocks, Warnings):
+ * man/groff.7.man (Conditional blocks):
+ * src/roff/troff/troff.1.man (Warnings): Document new warning
+ circumstance.
+
2026-04-21 G. Branden Robinson <[email protected]>
* src/roff/troff/input.cpp: Handle brace escape sequences
diff --git a/doc/groff.texi.in b/doc/groff.texi.in
index 114e9bb3b..ea82b13c4 100644
--- a/doc/groff.texi.in
+++ b/doc/groff.texi.in
@@ -16261,8 +16261,15 @@ These
@dfn{conditional blocks}
can furthermore be nested.
-Brace escape sequences outside of control structures have no meaning and
-produce no output.@c TODO: footnote: style warning
+Brace escape sequences outside of control structures have no meaning
+(but can be used as delimiters)
+and produce no output.@footnote{When its parser can tell
+that a brace escape sequence is useless,
+GNU
+@command{troff} @c GNU
+emits a warning in category
+@samp{style}.
+@xref{Warnings}.}
@DefescList {\@\{, , , }
@DefescListEnd {\@\}, , , }
@@ -22053,6 +22060,7 @@ ambiguous delimiters are accepted without warning.
Input was non-idiomatic or likely to produce an unexpected result
(or none at all),
but is not invalid:
+a brace escape sequence was employed uselessly;
the end of a sentence was detected prior to the end of a text line;
or
an attempt was made to combine temporary indentation
diff --git a/man/groff.7.man b/man/groff.7.man
index 45f1834f9..6762a96b1 100644
--- a/man/groff.7.man
+++ b/man/groff.7.man
@@ -2225,8 +2225,17 @@ These
.I "conditional blocks"
can furthermore be nested.
.
-Brace escape sequences outside of control structures have no meaning and
-produce no output.\" TODO: footnote: style warning
+Brace escape sequences outside of control structures have no meaning
+(but can be used as delimiters)
+and produce no output.
+.
+When its parser can tell that
+a brace escape sequence is useless,
+GNU
+.I troff \" GNU
+emits a warning in category
+.RB \[lq] style \[rq].
+.
.
.
.P
diff --git a/src/roff/troff/input.cpp b/src/roff/troff/input.cpp
index 57a49b1f8..1ee1edf62 100644
--- a/src/roff/troff/input.cpp
+++ b/src/roff/troff/input.cpp
@@ -1346,11 +1346,13 @@ static int read_character_in_copy_mode(node **nd,
(void) input_stack::get(0 /* nullptr */);
if (is_defining_macro)
return ESCAPE_LEFT_BRACE;
+ warning(WARN_STYLE, "left brace escape sequence is nilpotent");
break;
case '}':
(void) input_stack::get(0 /* nullptr */);
if (is_defining_macro)
return ESCAPE_RIGHT_BRACE;
+ warning(WARN_STYLE, "right brace escape sequence is nilpotent");
break;
case '`':
(void) input_stack::get(0 /* nullptr */);
diff --git a/src/roff/troff/troff.1.man b/src/roff/troff/troff.1.man
index 8e8cd4088..914dbb61e 100644
--- a/src/roff/troff/troff.1.man
+++ b/src/roff/troff/troff.1.man
@@ -853,6 +853,7 @@ style 16 T{
Input was non-idiomatic or likely to produce an unexpected result
(or none at all),
but is not invalid:
+a brace escape sequence was employed uselessly;
the end of a sentence was detected prior to the end of a text line;
or
an attempt was made to combine temporary indentation
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