diff --git a/.gitignore b/.gitignore
index 78c93ff..31eed88 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,4 @@ src/parseLEX.cpp
 *.swp
 *.eps
 *.plt
+.vscode/
diff --git a/Makefile b/Makefile
index 48d6523..96e220c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,18 +1,22 @@
-LEX		= flex
+LEX			= flex
 YACC		= bison
-LEX_FLAG  = -Pparse
-YACC_FLAG = -d -p parse
+LEX_FLAG  	= -Pparse
+YACC_FLAG 	= -d -p parse
 
-CXX       = g++
-#CFLAGS    = -g -Iinclude
-CFLAGS	 = -O3 -Iinclude -Wall
-CSRCS     = $(wildcard src/*.cpp)
-CHDRS     = $(wildcard include/*.h)
-#COBJS     = $(addsuffix .o, $(basename $(CSRCS)))
+CXX      	= g++
+CFLAGS	 	= -O3 -Iinclude -Wall
+CFLAGS_STFU	= -Wno-unused-function -Wno-unneeded-internal-declaration
+CSRCS     	= $(wildcard src/*.cpp)
+CHDRS     	= $(wildcard include/*.h)
 
-COBJS     = obj/main.o obj/simulator.o obj/circuit.o obj/utils.o obj/parseLEX.o obj/parseYY.o
+COBJS     	= obj/main.o obj/simulator.o obj/circuit.o obj/utils.o obj/parseLEX.o obj/parseYY.o
 
-all : bin/cspice
+.PHONY: create_dirs
+
+all : create_dirs bin/cspice
+
+create_dirs:
+	mkdir -p bin obj
 
 src/parseLEX.cpp: src/parser.l src/parseYY.hpp
 	@echo "> lexing: $<"
@@ -25,6 +29,10 @@ src/parseYY.cpp src/parseYY.hpp: src/parser.y
 	@mv parseYY.hpp src/parseYY.hpp
 	@ln -sf src/parseYY.hpp include/parseYY.hpp
 
+# Special rule for parseLEX.o to shut up warnings from autogenerated source
+obj/parseLEX.o : src/parseLEX.cpp
+	$(CXX) $(CFLAGS) ${CFLAGS_STFU} -c -o $@ $<
+
 obj/parseYY.o : src/parser.cpp
 
 bin/cspice : $(COBJS)
@@ -39,5 +47,6 @@ obj/%.o : src/%.cpp
 $(COBJS) : $(CHDRS)
 
 clean:
-	-rm -f obj/* bin/* src/parseYY.cpp src/parseYY.hpp src/parseLEX.cpp
+	-rm -f obj/*.o bin/cspice src/parseYY.cpp src/parseYY.hpp src/parseLEX.cpp
+	-rm -rf bin obj
 
diff --git a/include/parser.h b/include/parser.h
index b633e12..e4028b8 100644
--- a/include/parser.h
+++ b/include/parser.h
@@ -10,7 +10,7 @@ using namespace std;
 
 class Parser {
 public:
-   Parser(const char *) ;
+   Parser(const char* fname = nullptr) ;
    const Circuit& getCircuit() const { return circuit; }
    const vector<SimulateConfig>& getConfig() const { return config; }
    Circuit& getCircuit() { return circuit; }
diff --git a/include/source.h b/include/source.h
index 1e4b02f..1fdae38 100644
--- a/include/source.h
+++ b/include/source.h
@@ -11,8 +11,8 @@ class Source {
          _name() ,
          _prevValue(0.0) ,
          _nextValue(0.0) ,
-         _n1(NULL) ,
-         _n2(NULL) { }
+         _n1(0) ,
+         _n2(0) { }
 
       Source(const char * name , const int n1 , const int n2 , const double pv , const double nv) :
          _name(name) ,
diff --git a/include/utils.h b/include/utils.h
index fbbbec5..cd7d82a 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -13,7 +13,7 @@ extern void printFormula(const vector<vector<const Element*> > & , ostream &) ;
 extern complex<double> evalFormula(const vector<double> & , const double&);
 extern vector<pair<int , double> > expandFormula(const vector<vector<const Element*> > &) ;
 vector<double> numericalIntegration(const vector<double>& times,Simulator::TransferFunction& tf, unsigned shift = 8) ;
-extern unsigned long long hash(const char *) ;
+extern unsigned long long util_hash(const char *) ;
 
 #endif /* __UTILS_H__ */
 
diff --git a/src/circuit.cpp b/src/circuit.cpp
index 4c73e11..9ecee33 100644
--- a/src/circuit.cpp
+++ b/src/circuit.cpp
@@ -111,7 +111,7 @@ void Circuit::dfs(
          // Be ware that, we have to take the risk of
          // hash(a) + hash(b) == hash(c) + hash(d),
          // though I don't think it would happen so easily.
-         hashValue += hash(current_tree[i]->formula().c_str()) ;
+         hashValue += util_hash(current_tree[i]->formula().c_str()) ;
 
          sign *= current_tree[i]->sign() ;
       }
diff --git a/src/parser.cpp b/src/parser.cpp
index af3ca8b..f7521f7 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -1,4 +1,4 @@
-Parser::Parser(const char * fname = NULL) {
+Parser::Parser(const char * fname) {
    extern FILE * yyin ;
    extern int yyparse() ;
 
diff --git a/src/parser.l b/src/parser.l
index 620af0b..af637cd 100644
--- a/src/parser.l
+++ b/src/parser.l
@@ -282,7 +282,7 @@ FNAME (([0-9a-zA-Z\.\-_])+\.eps)
 .  {
       /* rest cases */
       char msg[40] ;
-      sprintf(msg , "Unexpected character: '%s'" , escape(yytext)) ;
+      snprintf(msg , 40, "Unexpected character: '%s'" , escape(yytext)) ;
       yyerror(msg) ;
       return yytext[0] ;
    }
diff --git a/src/utils.cpp b/src/utils.cpp
index cdb5f87..8e3e06f 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -98,7 +98,7 @@ ostream& operator<<(ostream& out , const Element& element) {
    return out ;
 }
 
-unsigned long long hash(const char * p) {
+unsigned long long util_hash(const char * p) {
    // using FNV-1a hash algorithm
    const unsigned long long prime = 1099511628211ull ;
    unsigned long long result = 14695981039346656037ull ;