fix potential undefined behaviour

fix #19

src/sdcv.cpp

@@ -157,7 +157,7 @@ int main(int argc, char *argv[]) try {
                   });
 
     std::list<std::string> order_list;
-    if (use_dict_list) {
+    if (use_dict_list != nullptr) {
         for (auto &&x : bookname_to_ifo) {
             gchar **p = get_impl(use_dict_list);
             for (; *p != nullptr; ++p)

src/stardict_lib.cpp

@@ -89,7 +89,6 @@ bool DictInfo::load_from_ifo_file(const std::string& ifofilename,
   if (!g_str_has_prefix(
           g_str_has_prefix(get_impl(buffer), (const gchar *)(utf8_bom)) ? get_impl(buffer) + 3 : get_impl(buffer),
           magic_data)) {
-    g_free(buffer);
     return false;
   }
 

src/utils.hpp

@@ -27,6 +27,14 @@ public:
 		}
 	}
 
+    friend inline bool operator==(const ResourceWrapper& lhs, nullptr_t) noexcept {
+        return !lhs.p_;
+    }
+
+    friend inline bool operator!=(const ResourceWrapper& lhs, nullptr_t) noexcept {
+        return !!lhs.p_;
+    }
+
 	friend inline T *get_impl(const ResourceWrapper& rw) {
 		return rw.p_;
 	}
@@ -39,21 +47,6 @@ private:
 	T *p_;
 
 	void free_resource() { if (p_) unref_res(p_); }
-
-// Helper for enabling 'if (sp)'
-	struct Tester {
-        Tester() {}
-    private:
-        void operator delete(void*);
-    };
-public:
-	// enable 'if (sp)'
-    operator Tester*() const {
-        if (!*this)
-            return 0;
-        static Tester t;
-        return &t;
-    }
 };
 
 namespace glib {