From patchwork Sat Feb 4 12:19:01 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [pulseaudio-discuss] iochannel: don't use variable length array in union From: Tanu Kaskinen X-Patchwork-Id: 136885 Message-Id: <20170204121901.17428-1-tanuk@iki.fi> To: pulseaudio-discuss@lists.freedesktop.org Date: Sat, 4 Feb 2017 14:19:01 +0200 Clang didn't like the variable length array: pulsecore/iochannel.c:358:17: error: fields must have a constant size: 'variable length array in structure' extension will never be supported uint8_t data[CMSG_SPACE(sizeof(int) * nfd)]; ^ Commit 451d1d6762 introduced the variable length array in order to have the correct value in msg_controllen. This patch reverts that commit and uses a different way to achieve the same goal. BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=99458 --- Upstream-Status: Backport Signed-off-by: Khem Raj src/pulsecore/iochannel.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/src/pulsecore/iochannel.c b/src/pulsecore/iochannel.c index 8ace297ff..897337522 100644 --- a/src/pulsecore/iochannel.c +++ b/src/pulsecore/iochannel.c @@ -355,7 +355,7 @@ ssize_t pa_iochannel_write_with_fds(pa_iochannel*io, const void*data, size_t l, struct iovec iov; union { struct cmsghdr hdr; - uint8_t data[CMSG_SPACE(sizeof(int) * nfd)]; + uint8_t data[CMSG_SPACE(sizeof(int) * MAX_ANCIL_DATA_FDS)]; } cmsg; pa_assert(io); @@ -382,7 +382,13 @@ ssize_t pa_iochannel_write_with_fds(pa_iochannel*io, const void*data, size_t l, mh.msg_iov = &iov; mh.msg_iovlen = 1; mh.msg_control = &cmsg; - mh.msg_controllen = sizeof(cmsg); + + /* If we followed the example on the cmsg man page, we'd use + * sizeof(cmsg.data) here, but if nfd < MAX_ANCIL_DATA_FDS, then the data + * buffer is larger than needed, and the kernel doesn't like it if we set + * msg_controllen to a larger than necessary value. The commit message for + * commit 451d1d6762 contains a longer explanation. */ + mh.msg_controllen = CMSG_SPACE(sizeof(int) * nfd); if ((r = sendmsg(io->ofd, &mh, MSG_NOSIGNAL)) >= 0) { io->writable = io->hungup = false;