Re: [XTF 2/4] lib: always append CR after LF in vsnprintf()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/04/2020 10:41, Pawel Wieczorkiewicz wrote:
> The explicit LFCR sequence guarantees proper line by line formatting
> in the output.
> The '\n' character alone on some terminals is not automatically
> converted to LFCR.
>
> Signed-off-by: Pawel Wieczorkiewicz <wipawel@xxxxxxxxx>

Up until now, all console destinations have expected POSIX text semantics.

I presume this is due to the COM1 use presented in the next patch?

Unfortunately, this comes with collateral damage.

# ./xtf-runner hvm64 example
Executing 'xl create -p tests/example/test-hvm64-example.cfg'
Executing 'xl console test-hvm64-example'
Executing 'xl unpause test-hvm64-example'
--- Xen Test Framework ---

Found Xen: 4.14

Environment: HVM 64bit (Long mode 4 levels)

Hello World

Test result: SUCCESS


Combined test results:
test-hvm64-example                       CRASH

which I believe is due to xenconsoled (or the intervening pty) also
expanding \n to \r\n (and "Test result:" no longer being on the final
line from xtf-runner's point of view).  Xen also expands \n to \r\n for
the console, so ends up emitting \r\r\n.

Would it be better to have the com1 console handler do the expansion
locally, to avoid interfering with the semantics of every other
destination?  That said...

> ---
>  common/libc/vsnprintf.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/common/libc/vsnprintf.c b/common/libc/vsnprintf.c
> index a49fd30..3202137 100644
> --- a/common/libc/vsnprintf.c
> +++ b/common/libc/vsnprintf.c
> @@ -285,6 +285,16 @@ int vsnprintf(char *buf, size_t size, const char *fmt, 
> va_list args)
>          if ( *fmt != '%' )
>          {
>              PUT(*fmt);
> +
> +            /*
> +             * The '\n' character alone on some terminals is not 
> automatically
> +             * converted to LFCR.
> +             * The explicit LFCR sequence guarantees proper line by line
> +             * formatting in the output.
> +             */
> +            if ( *fmt == '\n' && str < end )
> +                PUT('\r');

... doesn't this end up putting out \n\r ?

~Andrew

> +
>              continue;
>          }
>