#include <stdint.h>

typedef struct {
  uint16_t b;
  uint8_t a;
}  sometype;

 

#include "e.h"
extern __xdata sometype x;

void main(void) {
  x.a = 5;
}
 

#include "e.h"
__xdata sometype x;
 

c:tmpSDCC>sdcc -c e1.c

c:tmpSDCC>sdcc -c e.c

c:tmpSDCC>sdcc e.rel e1.rel

c:tmpSDCC>

                            120 ;	e.c:4: void main(void) {
                            121 ;	-----------------------------------------
                            122 ;	 function main
                            123 ;	-----------------------------------------
   0064                     124 _main:
                    0002    125 	ar2 = 0x02
                    0003    126 	ar3 = 0x03
                    0004    127 	ar4 = 0x04
                    0005    128 	ar5 = 0x05
                    0006    129 	ar6 = 0x06
                    0007    130 	ar7 = 0x07
                    0000    131 	ar0 = 0x00
                    0001    132 	ar1 = 0x01
                            133 ;	e.c:5: x.a = 5;
   0064 90 00 02            134 	mov	dptr,#(_x + 0x0002)
   0067 74 05               135 	mov	a,#0x05
   0069 F0                  136 	movx	@dptr,a
   006A 22                  137 	ret

 

Please go more into details with "does not work", and perhaps post a minimum example which exhibits the symptoms.

JW