From 94ad86b3e0c342f21ee9cac435621db7191575a4 Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@mit.edu>
Date: Wed, 4 Mar 2020 21:25:20 -0500
Subject: [PATCH] check for valid swig in configure script (#1144)

* check for valid swig in configure script

* tweak
---
 configure.ac       | 11 +++++++++++
 python/Makefile.am |  1 -
 scheme/Makefile.am |  1 -
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 5d2fbaabf..eb7b8c95f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -511,10 +511,21 @@ AC_TRY_COMPILE([], [_Pragma("ivdep")], [], [AC_DEFINE([_Pragma],[],[define to no
 
 # checks for python
 ##############################################################################
+
 AC_ARG_WITH(python,
 	[AC_HELP_STRING([--without-python], [compile without Python interface])],
         with_python=$withval,with_python=yes)
 
+AC_CHECK_PROG(SWIG, swig, swig, echo)
+if test "$USE_MAINTAINER_MODE" = yes && (test "x$with_python" = "xyes" || test "x$with_scheme" = "xyes") && test "x$SWIG" = xecho; then
+  AC_MSG_ERROR([SWIG not found; configure --without-python --without-scheme or use a release tarball])
+fi
+if test "$USE_MAINTAINER_MODE" = yes && test "x$with_python" = "xyes"; then
+  if ($SWIG -version | grep "SWIG Version 4" > /dev/null 2>&1); then
+    AC_MSG_ERROR([SWIG version 4 is not supported for Python; configure --without-python or use a release tarball])
+  fi
+fi
+
 if test "x$with_python" = xno; then
   have_python=no
 else
diff --git a/python/Makefile.am b/python/Makefile.am
index 97a042bdb..c7b5fa027 100644
--- a/python/Makefile.am
+++ b/python/Makefile.am
@@ -137,7 +137,6 @@ endif
 ##################################################
 if MAINTAINER_MODE
 
-SWIG ?= swig
 SWIG_VERSION = $(shell $(SWIG) -version | grep Version | awk '{print $$3}')
 MEEP_SWIG_SRC = meep.i numpy.i vec.i
 
diff --git a/scheme/Makefile.am b/scheme/Makefile.am
index df9b38966..79c6d3a9e 100644
--- a/scheme/Makefile.am
+++ b/scheme/Makefile.am
@@ -23,7 +23,6 @@ meep_wrap.o: meep_wrap.cxx $(srcdir)/meep-ctl-swig.hpp $(CTLHDRS)
 
 if WITH_LIBCTL
 if MAINTAINER_MODE
-SWIG ?= swig
 meep_wrap.cxx: meep.i meep_op_renames.i meep_enum_renames.i meep_renames.i ctl-io.i meep-ctl-swig.hpp meep_swig_bug_workaround.i $(LIBHDRS)
 	$(SWIG) -I$(top_srcdir)/src -c++ -guile -o $@ $(srcdir)/meep.i
 	patch -p0 $@ < $(srcdir)/meep_wrap.patch