From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35669) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T0JAr-0001WD-I6 for qemu-devel@nongnu.org; Sat, 11 Aug 2012 17:24:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1T0JAq-0008HS-D5 for qemu-devel@nongnu.org; Sat, 11 Aug 2012 17:24:45 -0400 From: Peter Maydell Date: Sat, 11 Aug 2012 22:24:35 +0100 Message-Id: <1344720275-26744-1-git-send-email-peter.maydell@linaro.org> Subject: [Qemu-devel] [PATCH] iov_send_recv(): Handle zero bytes case even if OS does not List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-trivial@nongnu.org, Michael Tokarev , patches@linaro.org POSIX allows sendmsg() and recvmsg() to fail EMSGSIZE if passed a zero msg.msg_iovlen (in particular the MacOS X implementation will do this). Handle the case where iov_send_recv() is passed a zero byte count explicitly, to avoid accidentally depending on the OS to treat zero msg_iovlen as a no-op. Signed-off-by: Peter Maydell --- This is what was causing 'make check' to fail on MacOS X. The other option was to declare that a zero bytecount was illegal, I guess. iov.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/iov.c b/iov.c index b333061..60705c7 100644 --- a/iov.c +++ b/iov.c @@ -146,6 +146,13 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, { ssize_t ret; unsigned si, ei; /* start and end indexes */ + if (bytes == 0) { + /* Catch the do-nothing case early, as otherwise we will pass an + * empty iovec to sendmsg/recvmsg(), and not all implementations + * accept this. + */ + return 0; + } /* Find the start position, skipping `offset' bytes: * first, skip all full-sized vector elements, */ -- 1.7.11.4