Re: AVR-GCC-list Digest, Vol 157, Issue 2

[Bob von Knobloch]

On 08/02/2020 18:00, address@hidden wrote:
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> Today's Topics:
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>     1. Re: Where is the error (stdout) (Col)
>     2. Re: Where is the error (stdout) (David Kelly)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 8 Feb 2020 12:58:19 +1300
> From: Col <address@hidden>
> To: address@hidden
> Subject: Re: Where is the error (stdout)
> Message-ID: <address@hidden>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
>
> > void uart_putchar(char c, FILE *stream)
> > {
> >   if (c == '\n')
> > uart_putchar('\r', stream);
> >   loop_until_bit_is_set(UCSRA, UDRE);
> >   UDR = c;
> >   return ;
> > }
> I suspect it's because your returning a void instead of an int,
>
> Here is some code that I used to test stdio on avrlibc ( atmega128 )
>
> which compiles fine with gcc 5.4.0
>
>
> static int uart_putchar(char c, FILE *stream)
> {
>       if (c == '\n')
>           uart_putchar('\r', stream);
>       loop_until_bit_is_set(UCSR0A, UDRE);
>       UDR0 = c;
>       return 0;
> }
>
>
>
>
> Cheers
>
> Colin
>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 7 Feb 2020 18:56:41 -0600
> From: David Kelly <address@hidden>
> To: address@hidden
> Subject: Re: Where is the error (stdout)
> Message-ID: <address@hidden>
> Content-Type: text/plain;       charset=us-ascii
>
>
> On Feb 7, 2020, at 5:58 PM, Col <address@hidden> wrote:
>
> > > void uart_putchar(char c, FILE *stream)
> > > {
> > >   if (c == '\n')
> > > uart_putchar('\r', stream);
> > >   loop_until_bit_is_set(UCSRA, UDRE);
> > >   UDR = c;
> > >   return ;
> > > }
> >
> > I suspect it's because your returning a void instead of an int,
>
> In Unix convention its
>
>         int putc( int, FILE* )
>         int putchar( int )
>
> Where upon success one returns the character put or -1 or EOF for failure. If 
> replacing standard function one should return the expected value else something 
> will break.
>
> --
> David Kelly N4HHE, address@hidden
> ============================================================
> Whom computers would destroy, they must first drive mad.
>
>
>
>
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> ------------------------------
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> End of AVR-GCC-list Digest, Vol 157, Issue 2
> ********************************************

I use a similar function on a Mega1284:

/**
 *******************************************************************************
 *      Wait until USART free, then send character to the terminal.
 *      Pad LF to CR,LF.
 *******************************************************************************
 */

static void term_putchar(uint8_t c)
{
    if (c == '\n')
        term_putchar('\r');
    loop_until_bit_is_set(UCSR0A, UDRE0);
    UDR0 = c;
}

Compiles and works fine (for me), possible the spurious 'return;' is doing 
something that the compiler doesn't like (need a GCC guru).

Cheers,
Bob