Disallow h// at the start of patterns

2 files changed, 6 insertions, 0 deletions

diff --git a/man/grab.1 b/man/grab.1
index 3521b9f..ab24337 100644
--- a/man/grab.1
+++ b/man/grab.1
@@ -234,6 +234,10 @@ letter,
 and highlights the capital letter(s):
 .Pp
 .Dl x/\ew+/ g/[A\-Z]/ h//
+.Pp
+The empty
+.Sq h
+operator is not permitted as the first operator in a pattern.
 .Sh ENVIRONMENT
 .Bl -tag -width GRAB_COLORS
 .It Ev GRAB_COLORS
diff --git a/src/grab.c b/src/grab.c
index 33943f0..f8f5471 100644
--- a/src/grab.c
+++ b/src/grab.c
@@ -302,6 +302,8 @@ comppat(char8_t *s)
 		if (s - p == 0) {
 			if (op.c != 'h')
 				diex("Empty regex given to ‘%c’", op.c);
+			if (ops.len == 0)
+				diex("Empty ‘h’ is not allowed as the first operator");
 			op.pat = ops.buf[ops.len - 1].pat;
 		} else
 			op.pat = mkregex(p, s - p);