Add necessary #include stddef.h directive

diff --git a/src/libpspp/argv-parser.h b/src/libpspp/argv-parser.h
index 3406ba216746e6d7d5aa4203da0487857a3599b2..6e6d83ff82cac17a4a0decc875b73ba4d1a6195a 100644 (file)
--- a/src/libpspp/argv-parser.h
+++ b/src/libpspp/argv-parser.h
@@ -37,6 +37,7 @@
 
 #include <getopt.h>
 #include <stdbool.h>
+#include <stddef.h>
 
 struct argv_option
   {