Stefan, I believe that your declarations for your pointer to a function is incorrect and might be ambiguous for some compilers.
I think this is the correct convention for a pointer to a function of type void with no arguments in C:

void (*functionptr)();

Try this code and see what you get:

#define __MAIN_C__
const char mychar1[6]="ABCDEF";
const char *mycharptr;
int mymode;
void xgetstr1(void);
void xgetstr2(void);
typedef struct 
 {int mode;
  void (*funcptr1)();
  const void (*funcptr2)();  
  } myoneset;

void xgetstr1(void){	mycharptr=&mychar1[0];}
void xgetstr2(void){	mycharptr=&mychar1[1];}
  
myoneset listofsets[2] =
 {{1,&xgetstr1,&xgetstr2}, {3,&xgetstr2,&xgetstr1}};

int main (void)
{
   const void (*myfuncptr)();
   int i ;
   mycharptr=&mychar1[0];
   mycharptr=&mychar1[2];			
	 	
   myfuncptr=&xgetstr1;
		
   myfuncptr=listofsets[0].funcptr1;
   myfuncptr=listofsets[1].funcptr2;
	
   myfuncptr=0;
 
   mymode=2;
   for (i=0;i<2;i++)
   {
      if (listofsets[0].mode==mymode)
         myfuncptr=listofsets[1].funcptr2;
   } 	
   return(0);
}