Calling C Code with nested structures with Simulink

I have to Call C Code (which I'm not allowed to modify) from a Simulink model. The Code relies heavily on nested structures as shown in the attached MWE.

example struct

typedef double* adjacent_p;
typedef double* opposite_p;

typedef struct {
    adjacent_p a;
    opposite_p b;
} triag_t;

I tried using Simulink.importExternalCTypes(), but get the following warning:

>> Simulink.importExternalCTypes('SimLinkMod')

Warning: 'triag_t' from file

'C:\[EDIT]\pythagoras.h'

is not imported. It has a field whose type is unsupported in Simulink.

Is there a possibility to make such a Code work in Simulink ?