--- spack-src/tools/seismic_2D-tools/m_getopt.f90.org	2020-05-13 10:14:41.822006522 +0900
+++ spack-src/tools/seismic_2D-tools/m_getopt.f90	2020-05-13 10:17:01.102690012 +0900
@@ -80,7 +80,9 @@
     character(256), allocatable :: argv(:)
     integer :: i
     character(256) :: optkey
-    
+
+    integer, external :: iargc
+
     narg = iargc()
     allocate( argv(1:narg) )