fix #439

Author: ludviggunne

main.cpp

@@ -60,6 +60,7 @@ int main(int argc, char **argv)
             case 's':
                 if (std::strncmp(arg, "-std=",5)==0) {
                     dui.std = arg + 5;
+                    dui.gnu = dui.std.rfind("gnu", 0) != std::string::npos;
                     found = true;
                 }
                 break;

simplecpp.cpp

@@ -2760,7 +2760,7 @@ static std::string extractRelativePathFromAbsolute(const std::string& absoluteSi
 static std::string openHeader(std::ifstream &f, const simplecpp::DUI &dui, const std::string &sourcefile, const std::string &header, bool systemheader);
 static void simplifyHasInclude(simplecpp::TokenList &expr, const simplecpp::DUI &dui)
 {
-    if (!isCpp17OrLater(dui))
+    if (!isCpp17OrLater(dui) && !dui.gnu)
         return;
 
     for (simplecpp::Token *tok = expr.front(); tok; tok = tok->next) {
@@ -3483,7 +3483,7 @@ void simplecpp::preprocess(simplecpp::TokenList &output, const simplecpp::TokenL
     // use a dummy vector for the macros because as this is not part of the file and would add an empty entry - e.g. /usr/include/poll.h
     std::vector<std::string> dummy;
 
-    const bool hasInclude = isCpp17OrLater(dui);
+    const bool hasInclude = isCpp17OrLater(dui) || dui.gnu;
     MacroMap macros;
     for (std::list<std::string>::const_iterator it = dui.defines.begin(); it != dui.defines.end(); ++it) {
         const std::string &macrostr = *it;

simplecpp.h

@@ -337,12 +337,13 @@ namespace simplecpp {
      * On the command line these are configured by -D, -U, -I, --include, -std
      */
     struct SIMPLECPP_LIB DUI {
-        DUI() : clearIncludeCache(false), removeComments(false) {}
+        DUI() : clearIncludeCache(false), removeComments(false), gnu(false) {}
         std::list<std::string> defines;
         std::set<std::string> undefined;
         std::list<std::string> includePaths;
         std::list<std::string> includes;
         std::string std;
+        bool gnu;
         bool clearIncludeCache;
         bool removeComments; /** remove comment tokens from included files */
     };