src: expr: fix build failure with json support

Fixes: e3f195777ee54 ("src: expr: remove expr_ops from struct expr")
Reported-by:  Mikhail Morfikov <mmorfikov@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/expression.h b/include/expression.h
index 18563325..b681b67f 100644
--- a/include/expression.h
+++ b/include/expression.h
@@ -168,6 +168,8 @@ struct expr_ops {
 					       const struct expr *expr);
 };
 
+const struct expr_ops *expr_ops(const struct expr *e);
+
 /**
  * enum expr_flags
  *