gbranden pushed a commit to branch master
in repository groff.
commit 142b8d93fc2e325d0f22aca5b683292304105002
Author: G. Branden Robinson <[email protected]>
AuthorDate: Thu Oct 8 06:06:19 2026 -0500
m4/groff.m4 (GROFF_G): Rewrite test.
...to rebalance its sensitivity vs. validity.
* m4/groff.m4 (GROFF_G): The test _was_ deciding that a build system's
installed `troff` was not GNU troff if, when given some *roff syntax
as input, it wrote `0` to its standard output. This means that a
`troff` that produced no output or interpolated `2` as the value of
the `.g` register would pass the test and make our configuration
process decide that a non-groff troff was _not_ installed. Flip the
sense of the test and check the `troff` command's output for an exact
match of `1`--that means the `troff` claims GNU troff compatibility.
---
ChangeLog | 13 +++++++++++++
m4/groff.m4 | 15 +++++++++------
2 files changed, 22 insertions(+), 6 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 421e7e29c..0c26571e0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2026-10-08 G. Branden Robinson <[email protected]>
+
+ * m4/groff.m4 (GROFF_G): Revise test to rebalance its
+ sensitivity vs. validity. The test _was_ deciding that a build
+ system's installed `troff` was not GNU troff if, when given some
+ *roff syntax as input, it wrote `0` to its standard output.
+ This means that a `troff` that produced no output or
+ interpolated `2` as the value of the `.g` register would pass
+ the test and make our configuration process decide that a
+ non-groff troff was _not_ installed. Flip the sense of the test
+ and check the `troff` command's output for an exact match of
+ `1`--that means the `troff` claims GNU troff compatibility.
+
2026-10-08 G. Branden Robinson <[email protected]>
* tmac/tmac.am ($(M4CHECK)): Revise recipe to work with what
diff --git a/m4/groff.m4 b/m4/groff.m4
index 07a9871e0..e4b952c97 100644
--- a/m4/groff.m4
+++ b/m4/groff.m4
@@ -1057,18 +1057,21 @@ AC_DEFUN([GROFF_TMAC],
])
-# Searching if a non-GNU Troff is installed. The built-in register
-# \n[.g] is always 1 in GNU Troff.
+# Check the build environment for a `troff` executable that defines a
+# built-in register `.g`. It always interpolates `1` in GNU troff.
+# If the build environment's troff does not thus advertise GNU troff
+# compatibility, assume that parallel installation of GNU troff
+# alongside the system's is desired.
AC_DEFUN([GROFF_G], [
g=
- AC_MSG_CHECKING([for existing troff installation])
+ AC_MSG_CHECKING([for an installed groff-incompatible troff])
if test "`(echo .tm '|n(.g' | tr '|' '\\\\' | troff -z -i 2>&1) \
- 2>/dev/null`" = 0
+ 2>/dev/null`" = 1
then
+ AC_MSG_RESULT([no])
+ else
AC_MSG_RESULT([yes])
g=g
- else
- AC_MSG_RESULT([no])
fi
AC_SUBST([g])
])
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