cgo option build

With this patch, we've made the external C parser optional for generateOutput.
As cgo can be problematic for some users, we've added an option to bypass it
and test generateOutput against a sample dot file instead. This change should
 make the tool more accessible and user-friendly.

Signed-off-by: Alessandro Carminati <[email protected]>
Suggested-by: Maurizio Papini <[email protected]>

Author: alessandrocarminati

.gitignore

@@ -1,3 +1,4 @@
 *.swp
 nav
 conf.json
+libdotparser.so

Makefile

@@ -1,6 +1,10 @@
+
 all:	nav.go
 	go build -ldflags="-r ."
 
+cgo:    nav.go dot_parser/libdotparser.so libdotparser.so
+	go build -ldflags="-r ." -tags CGO
+
 upx:	nav
 	upx nav
 
@@ -13,3 +17,13 @@ code/check:
 
 code/fmt:
 	@gofmt -w `find . -type f -name '*.go' -not -path "./vendor/*"`
+
+dot_parser/libdotparser.so: dot_parser/dot.l dot_parser/dot.y
+	$(MAKE) -C dot_parser/ libdotparser.so
+
+libdotparser.so: dot_parser/libdotparser.so
+	ln -s dot_parser/libdotparser.so libdotparser.so
+
+clean: 
+	$(MAKE) -C dot_parser/ clean
+	rm -f nav libdotparser.so

dot_parser/samples/xx.dot

@@ -0,0 +1,6 @@
+digraph G {
+rankdir="LR"
+"__x64_sys_getpid"->"__task_pid_nr_ns" 
+"__task_pid_nr_ns"->"__rcu_read_lock" 
+"__task_pid_nr_ns"->"__rcu_read_unlock" 
+}

libdotparser.so

@@ -1,25 +1,11 @@
+// +build !CGO
 /*
  * Copyright (c) 2022 Red Hat, Inc.
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
 package main
 
-/*
-#cgo LDFLAGS: -ldotparser -Ldot_parser/
-#include <stdio.h>
-#include "dot_parser/dot.tab.h"
-extern int dotparse(void);
-extern void set_input_string(const char* in);
-extern void end_lexical_scan(void);
-int parse_string(const char* in) {
-	set_input_string(in);
-	int rv = dotparse();
-	end_lexical_scan();
-	return rv;
-}
-*/
-import "C"
 import (
 	"encoding/binary"
 	"bytes"

nav.go

@@ -0,0 +1,25 @@
+// +build CGO
+package main
+
+/*
+#cgo LDFLAGS: -ldotparser -Ldot_parser/
+#include <stdio.h>
+#include "dot_parser/dot.tab.h"
+extern int dotparse(void);
+extern void set_input_string(const char* in);
+extern void end_lexical_scan(void);
+int parse_string(const char* in) {
+	set_input_string(in);
+	int rv = dotparse();
+	end_lexical_scan();
+	return rv;
+}
+*/
+import "C"
+
+func valid_dot(dot string) bool{
+	if C.parse_string(C.CString(dot))==0 {
+		return true
+		}
+	return false
+}