Re: [PATCH 1/4] treewide: Use 'z' length modifier for size_t/ssize_t conversions

On Thu, 30 Nov 2023 11:15:47 +1100
David Gibson <david(a)gibson.dropbear.id.au> wrote:

...
  On Wed, Nov 29, 2023 at 02:46:07PM +0100, Stefano
Brivio wrote:
  Types size_t and ssize_t are not necessarily
long, it depends on the
 architecture.   
 
 Most LGTM, but a couple of nits:
 
 [snip]
  @@ -106,7 +106,7 @@ void *packet_get_do(const
struct pool *p, size_t idx, size_t offset,
  
  	if (p->pkt[idx].offset + len + offset > p->buf_size) {
  		if (func) {
 -			trace("packet offset plus length %lu from size %lu, "
 +			trace("packet offset plus length %lu from size %zu, "   
 
 The change here is certainly correct.  But the remaining %lu is
 dubious.  The value given is the sum of a uint32_t and two size_t, so
 it could depend on platform what exactly that will be promoted to.  I
 think we should probably either cast the result explicitly to (size_t)
 and use %zu, or cast to (uint32_t) and use "%" PRIu32.
 
 [snip]
  diff --git a/tcp_splice.c b/tcp_splice.c
 index a5c1332..8d08bb4 100644
 --- a/tcp_splice.c
 +++ b/tcp_splice.c
 @@ -321,7 +321,7 @@ static int tcp_splice_connect_finish(const struct ctx *c,
  
  			if (fcntl(conn->pipe[side][0], F_SETPIPE_SZ,
  				  c->tcp.pipe_size)) {
 -				trace("TCP (spliced): cannot set %d->%d pipe size to %lu",
 +				trace("TCP (spliced): cannot set %d->%d pipe size to %zu",
  				      side, !side, c->tcp.pipe_size);
  			}
  		}
 @@ -554,7 +554,7 @@ retry:
  		readlen = splice(conn->s[fromside], NULL,
  				 conn->pipe[fromside][1], NULL, c->tcp.pipe_size,
  				 SPLICE_F_MOVE | SPLICE_F_NONBLOCK);
 -		trace("TCP (spliced): %li from read-side call", readlen);
 +		trace("TCP (spliced): %zi from read-side call", readlen);
  		if (readlen < 0) {
  			if (errno == EINTR)
  				goto retry;
 @@ -580,7 +580,7 @@ eintr:
  		written = splice(conn->pipe[fromside][0], NULL,
  				 conn->s[!fromside], NULL, to_write,
  				 SPLICE_F_MOVE | more | SPLICE_F_NONBLOCK);
 -		trace("TCP (spliced): %li from write-side call (passed %lu)",
 +		trace("TCP (spliced): %zi from write-side call (passed %zu)",
  		      written, to_write);   
 
 'to_write' is actually an ssize_t which would suggest %zi.  However
 looking at the code, I think to_write probably *should* be a size_t
 instead. 
Oops, I didn't notice. Well, I know we're passing it to splice(), but
we're also using it like this:

		if (!never_read && written < to_write) {
			to_write -= written;
			goto retry;
		}

so I'd rather keep it as ssize_t for the moment (and re-spin this
series with a %zi here), just in case we happen to do something silly
with it and ssize_t is saving us.

-- 
Stefano