c - strange Behavior of sdcc compiler for 8051 -

i used keil programming 8051 microcontrollers. reason have code in sdcc, today facing strange behavior in compiler. using code blocks ide 12.11 , sdcc 3.4 version.

i compiling simple piece of code.

#include <mcs51/8051.h> #include "serial.h"   unsigned char digits[5]={0};  void main(void) {     serial_init(-13);      digits[2]='a';     serial_send(digits[2]);     serial_send('a');      while(1)     {      }  } 

and here defination of serial_send function.

void serial_send(unsigned char dat){     while(!ti);     ti = 0;     sbuf = dat; } 

the problem that, according code should print 'a' character 2 times on terminal printing 1 time. problem in global veriable digits[] array.

the function work constant value not variable bassed argument.

i posting question here because think problem c language trick, unable figure out.

i tried re-installing compiler , ide both problem remains same. body please explain why happening. have tried different codes , in code constant , local variables works fine global variables providing strange behaviors.

check empty while loop while(!ti); not being optimised out compiler. main code ambiguous can't tell 'a' you're seeing being sent.

change of them 'b' , try swapping order of 2 serial_send() calls verify it's not case of sbuf being prematurely overwritten new data before uart has sent current byte.