On 03/15/2013 04:23 PM, Stephan Bergmann wrote:
I happened to run across a problem with current gvfsd-sftp in x86_64 Fedora 18 that is apparently due to bad code generated by GCC. The functionvoid g_vfs_read_channel_send_seek_offset (GVfsReadChannel *read_channel, goffset offset) { GVfsDaemonSocketProtocolReply reply; GVfsChannel *channel; channel = G_VFS_CHANNEL (read_channel); reply.type = g_htonl (G_VFS_DAEMON_SOCKET_PROTOCOL_REPLY_SEEK_POS); reply.seq_nr = g_htonl (g_vfs_channel_get_current_seq_nr (channel)); reply.arg1 = g_htonl (offset & 0xffffffff); reply.arg2 = g_htonl (offset >> 32); g_vfs_channel_send_reply (channel, &reply, NULL, 0); }in /usr/src/debug/gvfs-1.14.2/daemon/gvfsreadchannel.c shall split the signed 64 bit goffset offset into reply.arg1 and reply.arg2. What happens though is that reply.arg2 erroneously contains the same (byte-swapped, due to g_htonl) low-order 32 bits as reply.arg1. The generated code is
[...]
Is this a known problem with (Fedora 18's) GCC?
Grr, sorry for the noise; appears to be rather a bug in glib2-devel-2.34.2-2.fc18.x86_64, where /usr/include/glib-2.0/glib/gtypes.h
# define GUINT32_SWAP_LE_BE(val) ((guint32) __builtin_bswap32 ((gint32) val))
misses parentheses around "val", so the above
reply.arg2 = g_htonl (offset >> 32);
ultimately expands to
reply.arg2 = ((((guint32) __builtin_bswap32 ((gint32) offset >> 32))));
(and building gvfs with -Werror would have nicely given it away, "warning: right shift count >= width of type [enabled by default]").
Stephan -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
