Warn about TMPDIR

* doc/autoconf.texi (Initialization Macros): Warn about
setting TMPDIR, following up on this Paul Smith remark:
https://lists.gnu.org/r/autoconf/2022-10/msg00024.html

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index b6d4f0332de772736ad2fc7c2af2c52a76923aec..ed337fd6bf8b97a06f14b8f54831439b8abdb9ad 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -14610,6 +14610,10 @@ leave the temporary directory behind.  Hence it is important to use a
 @var{prefix} that makes it easier to determine if a leftover temporary
 directory from an interrupted script is safe to delete.
 
+If you set @code{TMPDIR=$tmp} after invoking this macro, you should
+reset @code{TMPDIR} before deleting the created directory, to avoid
+breaking commands that rely on @code{$TMPDIR}.
+
 The use of the output variable @samp{$tmp} rather than something in the
 @samp{as_} namespace is historical; it has the unfortunate consequence
 that reusing this otherwise common name for any other purpose inside