diff --git a/simplecpp.cpp b/simplecpp.cpp
@@ -2796,6 +2796,11 @@ class NonExistingFilesCache {
        m_pathSet.insert(path);
    }

private:
    std::set<std::string> m_pathSet;
    CRITICAL_SECTION m_criticalSection;
@@ -2807,22 +2812,18 @@ static NonExistingFilesCache nonExistingFilesCache;

static std::string openHeader(std::ifstream &f, const std::string &path)
{
-#ifdef SIMPLECPP_WINDOWS
    std::string simplePath = simplecpp::simplifyPath(path);
    if (nonExistingFilesCache.contains(simplePath))
        return "";  // file is known not to exist, skip expensive file open call
-
    f.open(simplePath.c_str());
    if (f.is_open())
        return simplePath;
-    else {
-        nonExistingFilesCache.add(simplePath);
-        return "";
-    }
-#else
-    f.open(path.c_str());
-    return f.is_open() ? simplecpp::simplifyPath(path) : "";
#endif
}

static std::string getRelativeFileName(const std::string &sourcefile, const std::string &header)
@@ -2907,6 +2908,11 @@ static bool hasFile(const std::map<std::string, simplecpp::TokenList *> &filedat

std::map<std::string, simplecpp::TokenList*> simplecpp::load(const simplecpp::TokenList &rawtokens, std::vector<std::string> &filenames, const simplecpp::DUI &dui, simplecpp::OutputList *outputList)
{
    std::map<std::string, simplecpp::TokenList*> ret;

    std::list<const Token *> filelist;
@@ -3032,6 +3038,11 @@ static std::string getTimeDefine(struct tm *timep)

void simplecpp::preprocess(simplecpp::TokenList &output, const simplecpp::TokenList &rawtokens, std::vector<std::string> &files, std::map<std::string, simplecpp::TokenList *> &filedata, const simplecpp::DUI &dui, simplecpp::OutputList *outputList, std::list<simplecpp::MacroUsage> *macroUsage, std::list<simplecpp::IfCond> *ifCond)
{
    std::map<std::string, std::size_t> sizeOfType(rawtokens.sizeOfType);
    sizeOfType.insert(std::make_pair("char", sizeof(char)));
    sizeOfType.insert(std::make_pair("short", sizeof(short)));

diff --git a/simplecpp.h b/simplecpp.h
@@ -314,12 +314,13 @@ namespace simplecpp {
     * On the command line these are configured by -D, -U, -I, --include, -std
     */
    struct SIMPLECPP_LIB DUI {
-        DUI() {}
        std::list<std::string> defines;
        std::set<std::string> undefined;
        std::list<std::string> includePaths;
        std::list<std::string> includes;
        std::string std;
    };

    SIMPLECPP_LIB long long characterLiteralToLL(const std::string& str);