Add attribute to clarify potential control flow.

tests/pio_write.c

@@ -22,6 +22,7 @@
 #endif
 
 #include "cdi.h"
+#include "error.h"
 #include "dmemory.h"
 #include "pio_write.h"
 #ifdef USE_MPI
@@ -60,6 +61,10 @@ static const struct {
   { "ieg", CDI_FILETYPE_IEG, CDI_DATATYPE_FLT64, GRID_LONLAT },
 };
 
+static void
+invalidOptionDie(const char *format, ...)
+  __attribute__((noreturn));
+
 static void
 invalidOptionDie(const char *format, ...)
 {