Add lint check for decrementing NF.

2 files changed, 12 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 119a42d8..7019b3f8 100755
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,11 @@
 	* builtin.c (do_print_rec): Restore check before calling get_field()
 	and add do_lint to the condition.
 
+	Unrelated:
+
+	* field.c (set_NF): Add lint warning if decrementing NF, which
+	doesn't work on older Unix awks.
+
 2018-09-16  gettextize  <bug-gnu-gettext@gnu.org>
 
 	* configure.ac (AM_GNU_GETTEXT_VERSION): Bump to 0.19.8.
diff --git a/field.c b/field.c
index b7723aa5..2f6eff70 100644
--- a/field.c
+++ b/field.c
@@ -396,6 +396,13 @@ set_NF()
 	nf = get_number_si(NF_node->var_value);
 	if (nf < 0)
 		fatal(_("NF set to negative value"));
+
+	static bool warned = false;
+	if (do_lint && NF > nf && ! warned) {
+		warned = true;
+		lintwarn(_("decrementing NF is not portable to many awk versions"));
+	}
+
 	NF = nf;
 
 	if (NF > nf_high_water)