Re: [Xen-devel] [PATCH v1 2/7] tools/livepatch: Set stdout and stderr unbuffered

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Dec 12, 2016 at 04:18:05PM +0000, Ross Lagerwall wrote:
> Using both stdout and stderr interleaved without newlines can result in
> strange output when using line buffered mode (e.g. a terminal) or when
> fully buffered (e.g. redirected to a file). Set both to unbuffered mode
> to fix this.
> 
> Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> ---
>  tools/misc/xen-livepatch.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/misc/xen-livepatch.c b/tools/misc/xen-livepatch.c
> index f6c7c8a..2f6721b 100644
> --- a/tools/misc/xen-livepatch.c
> +++ b/tools/misc/xen-livepatch.c
> @@ -330,7 +330,6 @@ int action_func(int argc, char *argv[], unsigned int idx)
>          }
>  
>          printf(".");
> -        fflush(stdout);
>          usleep(DELAY);
>      } while ( ++retry < RETRIES );
>  
> @@ -416,6 +415,13 @@ int main(int argc, char *argv[])
>  {
>      int i, j = 0, ret;
>  
> +    /*
> +     * Set stdout and stderr to be unbuffered to avoid having to fflush
> +     * when printing without a newline.
> +     */
> +    setvbuf(stdout, NULL, _IONBF, 0);
> +    setvbuf(stderr, NULL, _IONBF, 0);
> +

OOI why would you need to set stderr? It is unbuffered by default.

There is no harm in setting it though.

And perhaps you should check the return value of setvbuf?

Wei.

>      if ( argc  <= 1 )
>      {
>          show_help();
> -- 
> 2.7.4
> 

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