On Thu, May 29, 2025 at 01:08:58PM -0400, Jon Maloy wrote:
> Before doing an early exit any contents of stdout is normally flushed.
> This doesn't happen when the output goes into a pipe and we return with
> _exit(). We now add an explicit flush in such cases.

Minor nitpicking on this description.  AIUI

 * We'll *never* flush on exit with _exit(), not only when the output
   is a pipe
 * The reason we don't see the problem when stdout is a terminal is
   that in that case stdio flushes the buffer on each line

> Fixes: d0006fa784a7 ("treewide: use _exit() over exit()")
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> ---
>  conf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/conf.c b/conf.c
> index a6d7e22..a1d55a3 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -975,6 +975,7 @@ static void usage(const char *name, FILE *f, int status)
>  		"    SPEC is as described for TCP above\n"
>  		"    default: none\n");
>  
> +	fflush(f);
>  	_exit(status);
>  
>  pasta_opts:
> @@ -1029,6 +1030,7 @@ pasta_opts:
>  		"  --ns-mac-addr ADDR	Set MAC address on tap interface\n"
>  		"  --no-splice		Disable inbound socket splicing\n");
>  
> +	fflush(f);
>  	_exit(status);
>  }
>  
> @@ -1594,6 +1596,7 @@ void conf(struct ctx *c, int argc, char **argv)
>  			FPRINTF(stdout,
>  				c->mode == MODE_PASTA ? "pasta " : "passt ");
>  			FPRINTF(stdout, VERSION_BLOB);
> +			fflush(stdout);
>  			_exit(EXIT_SUCCESS);
>  		case 15:
>  			ret = snprintf(c->ip4.ifname_out,

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson