diff --git a/Makefile b/Makefile
index efc417d6..c38b3a2a 100644
--- a/Makefile
+++ b/Makefile
@@ -193,7 +193,7 @@ endif
 # header files.
 .PHONY: icg_sim_serv
 icg_sim_serv: $(ICG_EXE)
-	${TRICK_HOME}/bin/trick-ICG -s -m -n ${TRICK_CXXFLAGS} ${TRICK_SYSTEM_CXXFLAGS} ${TRICK_HOME}/include/trick/files_to_ICG.hh
+	${TRICK_HOME}/bin/trick-ICG -s -m ${TRICK_CXXFLAGS} ${TRICK_SYSTEM_CXXFLAGS} ${TRICK_HOME}/include/trick/files_to_ICG.hh
 
 # 1.1.1.4.1 Build the Interface Code Generator (ICG) executable.
 $(ICG_EXE) :
diff --git a/include/trick/ClassSizeCheck.hh b/include/trick/ClassSizeCheck.hh
new file mode 100644
index 00000000..b132f2d3
--- /dev/null
+++ b/include/trick/ClassSizeCheck.hh
@@ -0,0 +1,101 @@
+
+/**
+ * Provides a map of class/struct name and calculated size difference between ICG and runtime
+ */
+
+#ifndef CLASSSIZECHECK_HH
+#define CLASSSIZECHECK_HH
+
+#include <map>
+#include <string>
+#include <iostream>
+#include "trick/attributes.h"
+#include "trick/AttributesMap.hh"
+
+namespace Trick {
+
+/**
+ * These maps stores all the attributes by class/struct/enum name
+ * So these 2 classes could inherit from a template or something fancy, but
+ * they are so simple I decided to leave them separate.
+ */
+    struct ClassSizeDiffInfo {
+        int diff ;
+        std::string file_name ;
+        ClassSizeDiffInfo( int in_diff , std::string in_file_name ) :
+         diff(in_diff) , file_name(in_file_name) {}
+    } ;
+
+    class ClassSizeCheck {
+
+        public:
+            /**
+             * Returns a pointer to the singleton Trick::ClassSizeCheck instance.
+             * @return    A pointer to Trick::ClassSizeCheck
+             */
+            static ClassSizeCheck * class_size_check() {
+                if ( pInstance == NULL ) {
+                    pInstance = new Trick::ClassSizeCheck() ;
+                }
+                return pInstance ;
+            }
+            static void reset_instance() {
+                delete pInstance ;
+                pInstance = NULL ;
+            }
+
+            ClassSizeCheck() {} ;
+            ~ClassSizeCheck() {} ;
+
+            /**
+             * Adds a type and the corresponding attributes
+             * @param type    The name of the type.
+             * @param attr    Pointer to the attributes.
+             */
+            void add_diff( std::string type , ClassSizeDiffInfo diff_info ) {
+                name_to_diff.insert(std::pair<std::string,ClassSizeDiffInfo>(type,diff_info)) ;
+            }
+
+            /**
+             * Prints all the types that have a difference in size
+             */
+            void print_nonzero_diffs() {
+                std::map<std::string, ClassSizeDiffInfo>::iterator it ;
+                for ( it = name_to_diff.begin() ; it != name_to_diff.end() ; it++ ) {
+                    int curr_diff = it->second.diff ;
+                    ATTRIBUTES * attr = Trick::AttributesMap::attributes_map()->get_attr(it->first) ;
+                    unsigned int ii ;
+                    for ( ii = 0 ; attr[ii].name[0] != '\0'; ii++ ) {
+                        // Look for structured types that are not pointers
+                        std::map<std::string, ClassSizeDiffInfo>::iterator search_it ;
+                        if ( (attr[ii].type == TRICK_STRUCTURED) and
+                             ((attr[ii].num_index == 0) or (attr[ii].index[attr[ii].num_index-1].size != 0)) and
+                             ((search_it = name_to_diff.find(attr[ii].type_name)) != name_to_diff.end())
+                           ) {
+                            int num = 1 ;
+                            int jj ;
+                            // Calculate total number of structs in the variable
+                            for ( jj = 0 ; jj < attr[ii].num_index ; jj++ ) {
+                                num *= attr[ii].index[jj].size ;
+                            }
+                            // Subtract the combined difference
+                            curr_diff -= num * search_it->second.diff ;
+                        }
+                    }
+                    if ( curr_diff != 0 ) {
+                        std::cerr << it->first << " ICG size and runtime size do not match" << std::endl ;
+                        std::cerr << "Search for \"#ifndef TRICK_ICG\" within " << it->second.file_name << std::endl ;
+                    }
+                }
+            }
+
+        private:
+            std::map<std::string, ClassSizeDiffInfo> name_to_diff ;
+            static ClassSizeCheck * pInstance ;
+
+    } ;
+
+}
+
+#endif
+
diff --git a/libexec/trick/pm/gte.pm b/libexec/trick/pm/gte.pm
index 307543fb..97f3f823 100644
--- a/libexec/trick/pm/gte.pm
+++ b/libexec/trick/pm/gte.pm
@@ -88,6 +88,7 @@ sub gte (@) {
     $def{"TRICK_HOME"} = "$trick_home" ;
     $def{"TRICK_HOST_CPU_USER_SUFFIX"} = "" ;
     $def{"TRICK_ICGFLAGS"} = "" ;
+    $def{"TRICK_ICG_COMPAT15"} = "" ;
     $def{"TRICK_ICG_NOCOMMENT"} = "" ;
     $def{"TRICK_ICG_EXCLUDE"} = "" ;
     $def{"TRICK_SWIG_EXCLUDE"} = "" ;
diff --git a/libexec/trick/pm/s_source.pm b/libexec/trick/pm/s_source.pm
index aed69312..9b302b88 100644
--- a/libexec/trick/pm/s_source.pm
+++ b/libexec/trick/pm/s_source.pm
@@ -52,6 +52,7 @@ PURPOSE:
 
 #include \"trick/attributes.h\"
 #include \"trick/populate_attribute_maps.hh\"
+#include \"trick/ClassSizeCheck.hh\"
 
 #include \"trick/SimObject.hh\"
 #include \"trick/JobData.hh\"
@@ -178,6 +179,8 @@ PURPOSE:
 
     #---------------------------
     # Memory Init
+    print S_SOURCE "Trick::ClassSizeCheck * Trick::ClassSizeCheck::pInstance = NULL ;\n" ;
+
     print S_SOURCE "\n/* Memory Init */\n" ,
      "void memory_init( void ) {\n\n" ;
 
@@ -220,6 +223,8 @@ PURPOSE:
     print S_SOURCE $$sim_ref{create_connections} ;
 
     print S_SOURCE "\n" ,
+     " " x 4 , "Trick::ClassSizeCheck::class_size_check()->print_nonzero_diffs() ;\n" ,
+     " " x 4 , "Trick::ClassSizeCheck::reset_instance() ;\n" ,
      " " x 4 , "return ;\n" ,
      "}\n\n" ;
 
diff --git a/share/trick/makefiles/Makefile.common b/share/trick/makefiles/Makefile.common
index d7a5a4d7..acc41fca 100644
--- a/share/trick/makefiles/Makefile.common
+++ b/share/trick/makefiles/Makefile.common
@@ -40,6 +40,7 @@ export TRICK_CXXFLAGS
 export TRICK_LDFLAGS
 export TRICK_SFLAGS
 export TRICK_EXCLUDE
+export TRICK_ICG_COMPAT15
 export TRICK_ICG_EXCLUDE
 export TRICK_ICG_NOCOMMENT
 export TRICK_SWIG_EXCLUDE
diff --git a/trick_source/codegen/Interface_Code_Gen/ClassValues.cpp b/trick_source/codegen/Interface_Code_Gen/ClassValues.cpp
index ebc6d34b..55f73eb8 100644
--- a/trick_source/codegen/Interface_Code_Gen/ClassValues.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/ClassValues.cpp
@@ -8,7 +8,7 @@
 
 #ifdef __APPLE__
 #include "llvm/Support/CommandLine.h"
-extern llvm::cl::opt< bool > no_offset_of ;
+extern llvm::cl::opt< bool > global_compat15 ;
 #endif
 
 ClassValues::ClassValues() :
@@ -16,7 +16,8 @@ ClassValues::ClassValues() :
   is_pod(false) ,
   is_abstract(false) ,
   has_default_constructor(false) ,
-  has_public_destructor(false)
+  has_public_destructor(false),
+  compat15(false)
 {}
 
 ClassValues::~ClassValues() {
@@ -30,7 +31,7 @@ void ClassValues::addFieldDescription(FieldDescription * in_fdes) {
     field_descripts.push_back(in_fdes) ;
 
 #ifdef __APPLE__
-    if ( no_offset_of ) {
+    if ( !global_compat15 and !compat15 ) {
 #else
     {
 #endif
@@ -56,20 +57,23 @@ void ClassValues::addInheritedFieldDescriptions(std::vector<FieldDescription *>
 
     std::vector<FieldDescription *>::iterator fdit ;
     // Loop through the incoming inherited variable names
+    for ( fdit = in_fdes.begin() ; fdit != in_fdes.end() ; fdit++ ) {
+
+        (*fdit)->setBaseClassOffset( class_offset ) ;
+        (*fdit)->setInherited( true ) ;
+        (*fdit)->setVirtualInherited( virtual_inherited ) ;
+        // Adds the class offset to the field offset giving the total offset to the inherited variable
+        // The offset is stored in bits so multiply class_offset by 8.
+        (*fdit)->addOffset( class_offset * 8 ) ;
+    }
+
 #ifdef __APPLE__
-    if ( no_offset_of ) {
+    if ( !global_compat15 and !compat15 ) {
 #else
     {
 #endif
         for ( fdit = in_fdes.begin() ; fdit != in_fdes.end() ; fdit++ ) {
 
-            (*fdit)->setBaseClassOffset( class_offset ) ;
-            (*fdit)->setInherited( true ) ;
-            (*fdit)->setVirtualInherited( virtual_inherited ) ;
-            // Adds the class offset to the field offset giving the total offset to the inherited variable
-            // The offset is stored in bits so multiply class_offset by 8.
-            (*fdit)->addOffset( class_offset * 8 ) ;
-
             std::string in_name = (*fdit)->getName() ;
             // search existing names for incoming inherited variable name.
             std::map< std::string , FieldDescription * >::iterator mit = field_name_to_info_map.find(in_name) ;
@@ -203,6 +207,14 @@ bool ClassValues::isPOD() {
     return is_pod ;
 }
 
+void ClassValues::setSize(unsigned int in_size) {
+    size = in_size ;
+}
+
+unsigned int ClassValues::getSize() {
+    return size ;
+}
+
 void ClassValues::setAbstract(bool in_val) {
     is_abstract = in_val ;
 }
@@ -266,6 +278,14 @@ std::string ClassValues::getFullyQualifiedMangledTypeName() {
     return oss.str() ;
 }
 
+void ClassValues::setCompat15(bool in_val) {
+    compat15 = in_val ;
+}
+
+bool ClassValues::isCompat15() {
+    return compat15 ;
+}
+
 void ClassValues::print_namespaces(std::ostream & os, const char * delimiter) {
     unsigned int ii ;
     for ( ii = 0 ; ii < namespaces.size() ; ii++ ) {
diff --git a/trick_source/codegen/Interface_Code_Gen/ClassValues.hh b/trick_source/codegen/Interface_Code_Gen/ClassValues.hh
index 39234dbe..dcf45fea 100644
--- a/trick_source/codegen/Interface_Code_Gen/ClassValues.hh
+++ b/trick_source/codegen/Interface_Code_Gen/ClassValues.hh
@@ -68,6 +68,8 @@ class ClassValues : public ConstructValues {
         bool getHasInitAttrFriend() ;
         void setPOD(bool in_val) ;
         bool isPOD() ;
+        void setSize(unsigned int size) ;
+        unsigned int getSize() ;
         void setAbstract(bool in_val) ;
         bool isAbstract() ;
         void setHasDefaultConstructor(bool in_val) ;
@@ -78,6 +80,8 @@ class ClassValues : public ConstructValues {
         void setMangledTypeName( std::string in_val ) ;
         std::string getMangledTypeName() ;
         std::string getFullyQualifiedMangledTypeName() ;
+        void setCompat15(bool in_val) ;
+        bool isCompat15() ;
 
         void print_namespaces(std::ostream & os, const char * delimiter) ;
 
@@ -102,6 +106,9 @@ class ClassValues : public ConstructValues {
         /** Is this class plain old data? */
         bool is_pod ;
 
+        /** Size of class in bytes */
+        unsigned int size ;
+
         /** Is this class abstract? */
         bool is_abstract ;
 
@@ -113,6 +120,10 @@ class ClassValues : public ConstructValues {
 
         /** Mangled type name. Templates will have a mangled_type_name.  */
         std::string mangled_type_name ;
+
+        /** Generate Trick 15 compatible io_src code */
+        bool compat15 ;
+
 } ;
 
 #endif
diff --git a/trick_source/codegen/Interface_Code_Gen/ClassVisitor.cpp b/trick_source/codegen/Interface_Code_Gen/ClassVisitor.cpp
index e7f53bda..4ab3af05 100644
--- a/trick_source/codegen/Interface_Code_Gen/ClassVisitor.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/ClassVisitor.cpp
@@ -158,6 +158,8 @@ bool CXXRecordVisitor::VisitCXXRecordDecl( clang::CXXRecordDecl *rec ) {
           cs.hasICGNo(header_file_name) ) {
         return false ;
     }
+    cval.setCompat15(hsd.isPathInCompat15(rp)) ;
+    free(rp) ;
 
     // If this class needs a default constructor, then the complier will generate one and we can call it.
     if ( rec->needsImplicitDefaultConstructor() ) {
@@ -183,6 +185,8 @@ bool CXXRecordVisitor::VisitCXXRecordDecl( clang::CXXRecordDecl *rec ) {
     cval.setName(rec->getNameAsString()) ;
     cval.setPOD(rec->isPOD()) ;
 
+    cval.setSize(rec->getASTContext().getASTRecordLayout(rec).getSize().getQuantity()) ;
+
     clang::CXXRecordDecl::base_class_iterator bcii ;
 
     //std::cout << "parsing " << cval.getName() << std::endl ;
diff --git a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
index 1268f25c..357844a1 100644
--- a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
@@ -139,12 +139,12 @@ void HeaderSearchDirs::AddTrickSearchDirs () {
     }
 }
 
-void HeaderSearchDirs::AddICGExcludeDirs () {
+void HeaderSearchDirs::AddDirsAndFiles(std::string env_var, std::vector<std::string> & var_list) {
 
-    char * trick_icg_exclude = getenv("TRICK_ICG_EXCLUDE") ;
+    char * env_var_contents = getenv(env_var.c_str()) ;
 
-    if( trick_icg_exclude != NULL ) {
-        std::string s = std::string(trick_icg_exclude) ;
+    if( env_var_contents != NULL ) {
+        std::string s = std::string(env_var_contents) ;
         std::stringstream ss(s);
         std::string item;
         while(std::getline(ss, item, ':')) {
@@ -155,84 +155,13 @@ void HeaderSearchDirs::AddICGExcludeDirs () {
                     std::ifstream file_or_dir(resolved_path) ;
                     file_or_dir.seekg(0, std::ios::end) ;
                     if ( !file_or_dir.good()) {
-                        icg_exclude_dirs.push_back(std::string(resolved_path) + std::string("/"));
+                        var_list.push_back(std::string(resolved_path) + std::string("/"));
                     } else {
-                        icg_exclude_dirs.push_back(std::string(resolved_path));
+                        var_list.push_back(std::string(resolved_path));
                     }
                 } else {
-                    std::cout << bold(color(WARNING, "Warning")) << "    Cannot find TRICK_ICG_EXCLUDE directory " << quote(bold(item)) << std::endl ;
-                }
-            }
-        }
-    }
-}
-
-void HeaderSearchDirs::AddExcludeDirs () {
-
-    char * trick_exclude = getenv("TRICK_EXCLUDE") ;
-
-    if( trick_exclude != NULL ) {
-        std::string s = std::string(trick_exclude) ;
-        std::stringstream ss(s);
-        std::string item;
-        while(std::getline(ss, item, ':')) {
-            item = trim(item) ;
-            if ( ! item.empty() ) {
-                char * resolved_path = realpath(item.c_str(), NULL) ;
-                if ( resolved_path ) {
-                    std::ifstream file_or_dir(resolved_path) ;
-                    file_or_dir.seekg(0, std::ios::end) ;
-                    if ( !file_or_dir.good()) {
-                        exclude_dirs.push_back(std::string(resolved_path) + std::string("/"));
-                    } else {
-                        exclude_dirs.push_back(std::string(resolved_path));
-                    }
-                } else {
-                    std::cout << bold(color(WARNING, "Warning")) << "    Cannot find TRICK_EXCLUDE directory " << quote(bold(item)) << std::endl ;
-                }
-            }
-        }
-    }
-}
-
-void HeaderSearchDirs::AddExtLibDirs () {
-
-    char * trick_ext_lib_dirs = getenv("TRICK_EXT_LIB_DIRS") ;
-
-    if( trick_ext_lib_dirs != NULL ) {
-        std::string s = std::string(trick_ext_lib_dirs) ;
-        std::stringstream ss(s);
-        std::string item;
-        while(std::getline(ss, item, ':')) {
-            item = trim(item) ;
-            if ( ! item.empty() ) {
-                char * resolved_path = realpath(item.c_str(), NULL) ;
-                if ( resolved_path ) {
-                    ext_lib_dirs.push_back(std::string(resolved_path) + std::string("/"));
-                } else {
-                    std::cout << bold(color(WARNING, "Warning")) << "    Cannot find TRICK_EXT_LIB_DIRS directory " << quote(bold(item)) << std::endl ;
-                }
-            }
-        }
-    }
-}
-
-void HeaderSearchDirs::AddICGNoCommentDirs () {
-
-    char * trick_icg_nocomment = getenv("TRICK_ICG_NOCOMMENT") ;
-
-    if( trick_icg_nocomment != NULL ) {
-        std::string s = std::string(trick_icg_nocomment) ;
-        std::stringstream ss(s);
-        std::string item;
-        while(std::getline(ss, item, ':')) {
-            item = trim(item) ;
-            if ( ! item.empty() ) {
-                char * resolved_path = realpath(item.c_str(), NULL) ;
-                if ( resolved_path ) {
-                    icg_nocomment_dirs.push_back(std::string(resolved_path) + std::string("/"));
-                } else {
-                    std::cout << bold(color(WARNING, "Warning")) << "    Cannot find TRICK_ICG_NOCOMMENT directory " << quote(bold(item)) << std::endl ;
+                    std::cout << bold(color(WARNING, "Warning")) << "    Cannot find " <<
+                     env_var << " directory " << quote(bold(item)) << std::endl ;
                 }
             }
         }
@@ -260,11 +189,22 @@ void HeaderSearchDirs::addSearchDirs ( std::vector<std::string> & include_dirs )
     AddUserSearchDirs( include_dirs ) ;
     AddTrickSearchDirs() ;
     AddCompilerBuiltInSearchDirs() ;
-    AddExcludeDirs() ;
-    AddICGExcludeDirs() ;
-    AddExtLibDirs() ;
-    AddICGNoCommentDirs() ;
     ApplyHeaderSearchOptions() ;
+    AddDirsAndFiles("TRICK_ICG_EXCLUDE", icg_exclude_dirs) ;
+    AddDirsAndFiles("TRICK_EXCLUDE", exclude_dirs) ;
+    AddDirsAndFiles("TRICK_EXT_LIB_DIRS", ext_lib_dirs) ;
+    AddDirsAndFiles("TRICK_ICG_NOCOMMENT", icg_nocomment_dirs) ;
+
+    char * compat15_contents = getenv("TRICK_ICG_COMPAT15") ;
+    if ( compat15_contents != NULL ) {
+        std::string s(compat15_contents) ;
+        if ( s.length() > 0 ) {
+            s += std::string(":./S_source.hh") ;
+            setenv("TRICK_ICG_COMPAT15",s.c_str(),1) ;
+        }
+    }
+
+    AddDirsAndFiles("TRICK_ICG_COMPAT15", compat15_dirs) ;
 }
 
 bool HeaderSearchDirs::isPathInUserDir (const std::string& in_dir ) {
@@ -357,6 +297,18 @@ bool HeaderSearchDirs::isPathInICGNoComment (const std::string& in_file ) {
     return false ;
 }
 
+bool HeaderSearchDirs::isPathInCompat15 (const std::string& in_dir ) {
+
+    std::vector<std::string>::iterator vit ;
+    for ( vit = compat15_dirs.begin() ; vit != compat15_dirs.end() ; vit++ ) {
+        if ( ! in_dir.compare(0, (*vit).size(), (*vit))) {
+            return true ;
+        }
+    }
+
+    return false ;
+}
+
 std::string HeaderSearchDirs::getPathInExclude (const std::string& in_dir ) {
 
     std::vector<std::string>::iterator vit ;
diff --git a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.hh b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.hh
index 9209d5ee..ee6457b3 100644
--- a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.hh
+++ b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.hh
@@ -75,6 +75,13 @@ class HeaderSearchDirs {
           */
         bool isPathInICGNoComment (const std::string& path) ;
 
+        /** Returns true if directory is a subdirectory of a compatible 15 directory
+            in the TRICK_ICG_COMPAT15 environment variable.
+            @param path = directory path to be checked
+            @return true = path is in a system directory, false = not in system directory.
+          */
+        bool isPathInCompat15 (const std::string& path) ;
+
         /** Returns the TRICK_EXCLUDE directory that contains the path argument.
             @param path = path to be checked
             @return string from TRICK_EXCLUDE that contains the path.
@@ -126,17 +133,8 @@ class HeaderSearchDirs {
         /** Adds ${TRICK_HOME}/trick_source to the search directories */
         void AddTrickSearchDirs () ;
 
-        /** Create list of EXCLUDE directories  */
-        void AddExcludeDirs () ;
-
-        /** Create list of ICG_EXCLUDE directories  */
-        void AddICGExcludeDirs () ;
-
-        /** Create list of EXT_LIB_DIRS directories  */
-        void AddExtLibDirs () ;
-
-        /** Create list of ICG_NOCOMMENT directories  */
-        void AddICGNoCommentDirs () ;
+        /** Create list of directories  */
+        void AddDirsAndFiles(std::string env_var, std::vector<std::string> & var_list ) ;
 
         /** Apply all search directories to the preprocessor. */
         void ApplyHeaderSearchOptions () ;
@@ -153,6 +151,9 @@ class HeaderSearchDirs {
         /** List of directoris to exclude comments from the TRICK_ICG_NOCOMMENT environment variable */
         std::vector<std::string> icg_nocomment_dirs ;
 
+        /** List of directoris to write offsetof lines compatible with Trick 15 and earlier */
+        std::vector<std::string> compat15_dirs ;
+
         /** Map of file names to in icg_nocomment_dir used as a cache */
         std::map< std::string , bool > icg_nocomment_files ;
 } ;
diff --git a/trick_source/codegen/Interface_Code_Gen/PrintFileContents10.cpp b/trick_source/codegen/Interface_Code_Gen/PrintFileContents10.cpp
index 117db7ee..d28b7c32 100644
--- a/trick_source/codegen/Interface_Code_Gen/PrintFileContents10.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/PrintFileContents10.cpp
@@ -7,7 +7,7 @@
 #include "EnumValues.hh"
 #include "Utilities.hh"
 
-extern llvm::cl::opt< bool > no_offset_of ;
+extern llvm::cl::opt< bool > global_compat15 ;
 
 PrintFileContents10::PrintFileContents10() {}
 
@@ -35,6 +35,7 @@ void PrintFileContents10::printIOHeader(std::ostream & ostream , std::string hea
 "#include \"trick/MemoryManager.hh\"\n"
 "#include \"trick/attributes.h\"\n"
 "#include \"trick/parameter_types.h\"\n"
+"#include \"trick/ClassSizeCheck.hh\"\n"
 "#include \"trick/UnitsMap.hh\"\n"
 "#include \"trick/checkpoint_stl.hh\"\n"
 "#include \"" << header_file_name << "\"\n"
@@ -149,17 +150,7 @@ void PrintFileContents10::print_field_init_attr_stmts( std::ostream & ostream ,
  ClassValues * cv , unsigned int index ) {
 
     // For static variables replace the offset field with the address of the static variable
-    if ( no_offset_of ) {
-        if ( fdes->isStatic() ) {
-            ostream << "    attr" ;
-            printNamespaces( ostream, cv , "__" ) ;
-            printContainerClasses( ostream, cv , "__" ) ;
-            ostream << cv->getMangledTypeName() << "[" << index << "].offset = (long)(void *)&" ;
-            printNamespaces( ostream, cv , "::" ) ;
-            printContainerClasses( ostream, cv , "::" ) ;
-            ostream << cv->getName() << "::" << fdes->getName() << " ;\n" ;
-        }
-    } else {
+    if ( global_compat15 or cv->isCompat15()) {
         if ( fdes->isStatic() ) {
             // print a special offsetof statement if this is a static
             ostream << "    attr" ;
@@ -206,6 +197,16 @@ void PrintFileContents10::print_field_init_attr_stmts( std::ostream & ostream ,
             printContainerClasses( ostream, cv , "::" ) ;
             ostream << cv->getMangledTypeName() << "," << fdes->getName() << ") ;\n" ;
         }
+    } else {
+        if ( fdes->isStatic() ) {
+            ostream << "    attr" ;
+            printNamespaces( ostream, cv , "__" ) ;
+            printContainerClasses( ostream, cv , "__" ) ;
+            ostream << cv->getMangledTypeName() << "[" << index << "].offset = (long)(void *)&" ;
+            printNamespaces( ostream, cv , "::" ) ;
+            printContainerClasses( ostream, cv , "::" ) ;
+            ostream << cv->getName() << "::" << fdes->getName() << " ;\n" ;
+        }
     }
 
     if ( fdes->isSTL()) {
@@ -299,6 +300,21 @@ void PrintFileContents10::print_init_attr_func( std::ostream & ostream , ClassVa
         ostream << "    typedef " << cv->getName() << " " << cv->getMangledTypeName() << " ;\n\n" ;
     }
 
+    if ( !global_compat15 and !cv->isCompat15()) {
+        ostream << "    if ( sizeof(" ;
+        printNamespaces( ostream, cv , "::" ) ;
+        printContainerClasses( ostream, cv , "::" ) ;
+        ostream << cv->getName() << ") > " << cv->getSize() << ") {\n" ;
+        ostream << "        Trick::ClassSizeCheck::class_size_check()->add_diff(\"" ;
+        printNamespaces( ostream, cv , "::" ) ;
+        printContainerClasses( ostream, cv , "::" ) ;
+        ostream << cv->getName() << "\" , Trick::ClassSizeDiffInfo((sizeof(" ;
+        printNamespaces( ostream, cv , "::" ) ;
+        printContainerClasses( ostream, cv , "::" ) ;
+        ostream << cv->getName() << ") - " << cv->getSize() << ") , \"" << cv->getFileName() << "\")) ;\n" ;
+        ostream << "    }\n" ;
+    }
+
     unsigned int ii = 0 ;
     for ( fit = cv->field_begin() ; fit != cv->field_end() ; fit++ ) {
         if ( determinePrintAttr(cv , *fit) ) {
diff --git a/trick_source/codegen/Interface_Code_Gen/PrintFileContentsBase.cpp b/trick_source/codegen/Interface_Code_Gen/PrintFileContentsBase.cpp
index 96e9d269..56004f3b 100644
--- a/trick_source/codegen/Interface_Code_Gen/PrintFileContentsBase.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/PrintFileContentsBase.cpp
@@ -12,7 +12,7 @@
 #include "ClassValues.hh"
 #include "EnumValues.hh"
 
-extern llvm::cl::opt< bool > no_offset_of ;
+extern llvm::cl::opt< bool > global_compat15 ;
 
 PrintFileContentsBase::PrintFileContentsBase() {}
 
@@ -77,7 +77,15 @@ void PrintFileContentsBase::print_close_extern_c(std::ostream & ostream) {
 */
 bool PrintFileContentsBase::determinePrintAttr( ClassValues * c , FieldDescription * fdes ) {
     if ( fdes->getTypeName().compare("void") and fdes->getIO() != 0 and fdes->getEnumString().compare("TRICK_VOID")) {
-        if ( no_offset_of ) {
+        if ( global_compat15 or c->isCompat15()) {
+            if ( fdes->isInherited() ) {
+                return ((c->getHasInitAttrFriend() && fdes->getAccess() == clang::AS_protected)
+                     || (fdes->getAccess() == clang::AS_public)) ;
+            } else {
+                return (c->getHasInitAttrFriend()
+                    || (fdes->getAccess() == clang::AS_public)) ;
+            }
+        } else {
             if ( fdes->isStatic() ) {
                 if ( fdes->isInherited() ) {
                     return ((c->getHasInitAttrFriend() && fdes->getAccess() == clang::AS_protected)
@@ -89,14 +97,7 @@ bool PrintFileContentsBase::determinePrintAttr( ClassValues * c , FieldDescripti
             } else {
                 return true ;
             }
-        } else {
-            if ( fdes->isInherited() ) {
-                return ((c->getHasInitAttrFriend() && fdes->getAccess() == clang::AS_protected)
-                     || (fdes->getAccess() == clang::AS_public)) ;
-            } else {
-                return (c->getHasInitAttrFriend()
-                    || (fdes->getAccess() == clang::AS_public)) ;
-            }
+
         }
     }
     return false ;
diff --git a/trick_source/codegen/Interface_Code_Gen/main.cpp b/trick_source/codegen/Interface_Code_Gen/main.cpp
index bb276820..cb4aabba 100644
--- a/trick_source/codegen/Interface_Code_Gen/main.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/main.cpp
@@ -40,8 +40,8 @@ llvm::cl::alias force_alias("force" , llvm::cl::desc("Alias for -f") , llvm::cl:
 llvm::cl::list<std::string> input_file_names(llvm::cl::Positional, llvm::cl::desc("<input_file>"), llvm::cl::ZeroOrMore);
 llvm::cl::list<std::string> sink(llvm::cl::Sink, llvm::cl::ZeroOrMore);
 llvm::cl::list<std::string> pre_compiled_headers("include", llvm::cl::Prefix, llvm::cl::desc("pre-compiled headers"), llvm::cl::value_desc("pre_compiled_headers"));
-llvm::cl::opt<bool> no_offset_of("n", llvm::cl::desc("Do not print the offsetof calculations in attributes"));
-llvm::cl::alias no_offset_of_alias("no-offset-of" , llvm::cl::desc("Alias for -n") , llvm::cl::aliasopt(no_offset_of));
+llvm::cl::opt<bool> global_compat15("c", llvm::cl::desc("Print the offsetof calculations in attributes"));
+llvm::cl::alias compat15_alias("compat15", llvm::cl::desc("Alias for -c"), llvm::cl::aliasopt(global_compat15));
 
 /**
 Most of the main program is pieced together from examples on the web. We are doing the following: