microblaze getchar() not functioning properly

[Jeff Kenton]

On 07/28/2011 07:30 AM, naga raj wrote:
> Hi Mike,
>
>> Post the code which actually failed, after you have verified the failure.
> Following is the code which has some problem with getchar() function.
>
> #include<stdio.h>
>   volatile int i,j=0;
>   int main()
> {
>     char buf[10];
>     xil_printf("main\n");
>       while(j<6)
>     {
>         i=getchar();
>         xil_printf("input value of i is:%c\n",i);
>         buf[j]=i;
>         xil_printf("value of j is:%d\n",j);
>        j++;
>     }
>         xil_printf("buffer contains:%s\n",buf);
>         return 0;
> }
>
> I have given input as abc
> .
> I have observed following output:
>
>   main
>   input value of i is:a           ---------->my input ( I have not
> pressed any key after entering 'a')
>   value of j is:0
>   input value of i is:             ------------->  It is automatically
> skipping to take my input
>   value of j is:1
>
>
>   input value of i is:b           ---------->my input ( I have not
> pressed any key after entering 'b')
>   value of j is:2
>   input value of i is:              ------------->  It is automatically
> skipping to take my input
>   value of j is:3
>
>
>   input value of i is:c           ---------->my input ( I have not
> pressed any key after entering 'c')
>   value of j is:4
>   input value of i is:             ------------->  It is automatically
> skipping to take my input
>   value of j is:5
>
>    buffer contains: a
>
>
> If we observe it is waiting for user input when the value of variable
> j is 0, 2 and 4.
>
> I have given the input to the program using HyperTerminal. I have
> entered only abc as my input.
>
>> Look at the assembly generated by gcc.  Where is j incremented?
> I have observed the code generated for j++ it is correct.
> Please look into the below objdump code.
>   j++;
> 880002c8:	b0008800 	imm	-30720
> 880002cc:	e8603d88 	lwi	r3, r0, 15752
> 880002d0:	30630001 	addik	r3, r3, 1
> 880002d4:	b0008800 	imm	-30720
> 880002d8:	f8603d88 	swi	r3, r0, 15752
>
>> Why do you think that this is a problem in getchar()?
> With the above observation I am thinking that getchar() function is
> appending a null character after each character.
>
> Can you please give me some inputs so that I can proceed further.
>
> Thanks in advance,
> Nagaraju

Attach gdb to your process and put a breakpoint in the loop.  printf() 
is not the best way to debug problems.

--jeff