T3644: build: replace GCC preprocessor with a Python script for template expansions

2 files changed, 51 insertions, 12 deletions

diff --git a/Makefile b/Makefile
index f029225f2..84dbab401 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,6 @@ BUILD_DIR := build
 DATA_DIR := data
 SHIM_DIR := src/shim
 XDP_DIR := src/xdp
-CC := gcc
 LIBS := -lzmq
 CFLAGS :=
 
@@ -15,18 +14,8 @@ op_xml_obj = $(op_xml_src:.xml.in=.xml)
 
 %.xml: %.xml.in
 	@echo Generating $(BUILD_DIR)/$@ from $<
-	# -ansi      This turns off certain features of GCC that are incompatible
-	#            with ISO C90. Without this regexes containing '/' as in an URL
-	#            won't work
-	# -x c       By default GCC guesses the input language from its file extension,
-	#            thus XML is unknown. Force it to C language
-	# -E         Stop after the preprocessing stage
-	# -undef     Do not predefine any system-specific or GCC-specific macros.
-	# -nostdinc  Do not search the standard system directories for header files
-	# -P         Inhibit generation of linemarkers in the output from the
-	#            preprocessor
 	mkdir -p $(BUILD_DIR)/$(dir $@)
-	@$(CC) -x c-header -C -E -undef -nostdinc -P -I$(CURDIR)/$(dir $<) -o $(BUILD_DIR)/$@ -c $<
+	$(CURDIR)/scripts/transclude-template $< > $(BUILD_DIR)/$@
 
 .PHONY: interface_definitions
 .ONESHELL:
diff --git a/scripts/transclude-template b/scripts/transclude-template
new file mode 100755
index 000000000..5c6668a84
--- /dev/null
+++ b/scripts/transclude-template
@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+#
+# transclude-template: preprocessor for XML interface definitions to
+# interpret #include statements to include nested XML fragments and
+# snippets in documents.
+#
+# Copyright (C) 2021 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+#
+
+import os
+import re
+import sys
+
+regexp = re.compile(r'^ *#include <(.+)>$')
+
+def parse_file(filename):
+    lines = ""
+    with open(filename, 'r') as f:
+        while True:
+            line = f.readline()
+            if line:
+                result = regexp.match(line)
+                if result:
+                    lines += parse_file(os.path.join(directory, result.group(1)))
+                else:
+                    lines += line
+            else:
+                return lines
+
+if __name__ == '__main__':
+    if len(sys.argv) < 2:
+        print('Must specify XML file!', file=sys.stderr)
+        sys.exit(1)
+    filename = sys.argv[1]
+    directory = os.path.dirname(os.path.abspath(filename))
+    print(parse_file(filename))
+