diff --git a/shadersource.cpp b/shadersource.cpp
index 4910d10..5ec0e80 100644
--- a/shadersource.cpp
+++ b/shadersource.cpp
@@ -1,15 +1,31 @@
 #include "shadersource.h"
 #include <string>
+#include <sstream>
 #include "shader.h"
 
-ShaderSource::ShaderSource();
+#include <iostream>
+
+ShaderSource::ShaderSource()
+{
+    for(int i=0; i<NB_TYPES; ++i)
+        sources[i] = NULL;
+}
+
+ShaderSource::~ShaderSource()
+{
+    for(int i=0; i<NB_TYPES; ++i)
+        if(sources[i] != NULL)
+            delete(sources[i]);
+}
 
 void ShaderSource::addSource(const char *source, SourceType type)
 {
-
+    if(sources[type] != NULL)
+        delete(sources[type]);
+    sources[type] = new std::string(source);
 }
 
-Shader* ShaderSource::compile(int nbDefines = 0, const char** defines = NULL)
+Shader* ShaderSource::compile(int nbDefines, const char** defines)
 {
     if(sources[VERTEX] == NULL || sources[FRAGMENT] == NULL)
         return NULL;
@@ -18,8 +34,7 @@ Shader* ShaderSource::compile(int nbDefines = 0, const char** defines = NULL)
     {
         if(sources[i] == NULL)
             continue;
-        compiledSources[i] = std::string(sources[i]);
-        preprocess(compiledSources[i], nbDefines, defines);
+        compiledSources[i] = preprocess(*(sources[i]), nbDefines, defines);
     }
     if(sources[GEOMETRY] != NULL)
         return new Shader(compiledSources[VERTEX], compiledSources[GEOMETRY], compiledSources[FRAGMENT]);
@@ -27,14 +42,39 @@ Shader* ShaderSource::compile(int nbDefines = 0, const char** defines = NULL)
         return new Shader(compiledSources[VERTEX], compiledSources[FRAGMENT]);
 }
 
-void ShaderSource::preprocess(std::string &source, int nbDefines, const char** defines)
+bool isDefined(const std::string &str, int nbDefines, const char** defines)
 {
-    std::istringstream f("line1\nline2\nline3");
-    std::string line;
-    while (std::getline(f, line)) {
-        if(line.at(0) == '#')
-        {
-            // TODO
-        }
+    for(int i=0; i<nbDefines; ++i)
+    {
+        if(str.compare(defines[i]) == 0)
+            return true;
     }
+    return false;
+}
+
+std::string ShaderSource::preprocess(std::string source, int nbDefines, const char** defines)
+{
+    std::string compiled = "";
+    std::istringstream ss(source);
+    std::string line;
+    bool allowed = true;
+    while (std::getline(ss, line)) {
+        if(line.size() > 0 && line.at(0) == '#')
+        {
+            if(line.compare(0, 8, "#version") == 0)
+                compiled.append(line+'\n');
+            else if(line.compare(0, 7, "#ifdef ") == 0)
+                allowed = isDefined(line.substr(7), nbDefines, defines);
+            else if(line.compare(0, 8, "#ifndef ") == 0)
+                allowed = !isDefined(line.substr(8), nbDefines, defines);
+            else if(line.compare("#endif") == 0)
+                allowed = true;
+            else if(line.compare("#else") == 0)
+                allowed = !allowed;
+        }
+        else if(allowed)
+            compiled.append(line+'\n');
+    }
+    std::cout << compiled << std::endl;
+    return compiled;
 }
diff --git a/shadersource.h b/shadersource.h
index 3ea302d..78512be 100644
--- a/shadersource.h
+++ b/shadersource.h
@@ -17,15 +17,16 @@ public:
     };
 
     ShaderSource();
+    ~ShaderSource();
 
     void addSource(const char *source, SourceType type);
 
     Shader* compile(int nbDefines = 0, const char** defines = NULL);
 
 private:
-    char* sources[NB_TYPES];
+    std::string* sources[NB_TYPES];
 
-    void preprocess(std::string &source, int nbDefines, const char** defines);
+    std::string preprocess(std::string source, int nbDefines, const char** defines);
 };
 
 #endif // SHADERSOURCE_H