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From patchwork Sat Feb 4 12:19:01 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
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Subject: [pulseaudio-discuss] iochannel: don't use variable length array in
union
From: Tanu Kaskinen <tanuk@iki.fi>
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 <raj.khem@gmail.com>
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;
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