Ext_U and Ext_Y structures created in code when signals are defined as extern (ImportFromFile or ImportedExtern)

I have multiple models for which the code is generated separately. They all use the same signals defined in a .m file as follows:

x1 = Simulink.Signal;

x1.CoderInfo.StorageClass = 'Custom';

x1.CoderInfo.CustomStorageClass = 'ImportFromFile';

x1.CoderInfo.CustomAttributes.HeaderFile = 'xx_data.h';

I have also tried

x1 = Simulink.Parameter;

and

x1.CoderInfo.StorageClass = 'ImportedExtern';

The appropriate storage is in the xx_data .h file

The generated .h file contains the structures as follows:

typedef struct {

uint32_T x1;

boolean_T y1;

} ExtU_modelx_T;

typedef struct {

boolean_T z1;

} ExtY_modelx_T;

I don't want the signals defined in the .c/.h file, as they are in the xx_data.h file

which is in the modelx_private_types.h file. (#include <xx_data.h>)

This worked correctly in 2008b, which is previous version of these models.

My codegen file had the following parameters set (from 2008b)

set_param(cs,'BlockReduction','on');

set_param(cs,'InlineParams','on');

set_param(cs,'BooleanDataType','on');

set_param(cs,'ConditionallyExecuteInputs','on');

set_param(cs,'ParameterPooling','on');

set_param(cs,'OptimizeBlockIOStorage','on');

set_param(cs,'BufferReuse','on');

set_param(cs,'CombineOutputUpdateFcns','on');

sset_param(cs,'ExpressionFolding','on');

set_param(cs,'ForceParamTrailComments','on');

set_param(cs,'GenCodeOnly','on');

set_param(cs,'GlobalDataDefinition','Auto'); % InSourceFile, InSeparateSourceFile

set_param(cs,'GlobalDataReference','Auto'); %InSourceFile, InSeparateHeaderFile

set_param(cs,'GRTInterface','off');

set_param(cs,'IgnoreCustomStorageClasses','off');

set_param(cs,'IncDataTypeInIds','off');

set_param(cs,'IncHierarchyInIds','off');

set_param(cs,'IncludeFileDelimiter','UseBracket'); %Auto, UseQuote

set_param(cs,'IncludeHyperlinkInReport','off');

set_param(cs,'IncludeMdlTerminateFcn','off');

set_param(cs,'InitialValueSource','Model'); %DataObject

set_param(cs,'InlineInvariantSignals','on');

set_param(cs,'InlinedParameterPlacement','Hierarchical'); %NonHierarchical

set_param(cs,'InlinedPrmAccess','Literals'); %Macros

set_param(cs,'DefaultParameterBehavior','Inlined'); %Macros

set_param(cs,'InsertBlockDesc','on');

set_param(cs,'LocalBlockOutputs','on');

set_param(cs,'LogVarNameModifier','none');

set_param(cs,'MangleLength','1');

set_param(cs,'MatFileLogging','off');

set_param(cs,'CodeInterfacePackaging','Nonreusable function');

set_param(cs,'MultiInstanceErrorCode','Error'); %None, Warning

sset_param(cs,'OptimizeModelRefInitCode','off');

set_param(cs,'ParamNamingRule','None'); %UpperCase, LowerCase, Custom

set_param(cs,'PrefixModelToSubsysFcnNames','on');

set_param(cs,'ShowEliminatedStatement','off');

set_param(cs,'SignalNamingRule','None');

set_param(cs,'ZeroExternalMemoryAtStartup','off');

set_param(cs,'ZeroInternalMemoryAtStartup','off');