On Wed, 2016-01-13 at 10:08 +0100, Roger Pau Monné wrote: > El 13/01/16 a les 4.19, Doug Goldstein ha escrit: > > On 1/12/16 7:14 AM, Roger Pau Monne wrote: > > > According to the FreeBSD sysconf man page [0] if the variable is > > > associated > > > with functionality that is not supported, -1 is returned and errno is > > > not > > > modified. Modify libxl__dm_runas_helper so it's able to correctly > > > deal with this situation by setting the initial buffer value to 2048. > > > > > > [0] https://www.freebsd.org/cgi/man.cgi?query=sysconf
http://pubs.opengroup.org/onlinepubs/9699919799/functions/sysconf.html (whi ch IMHO is the more canonical documentation) describes a similar error behaviour, although for a subtly different case (no limit for the given variable). > > > > > > Signed-off-by: Roger Pau Monné <roger....@citrix.com> > > > --- > > > tools/libxl/libxl_dm.c | 7 +++++++ > > > 1 file changed, 7 insertions(+) > > > > > > diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c > > > index 0aaefd9..ec8fb51 100644 > > > --- a/tools/libxl/libxl_dm.c > > > +++ b/tools/libxl/libxl_dm.c > > > @@ -728,7 +728,14 @@ static int libxl__dm_runas_helper(libxl__gc *gc, > > > const char *username) > > > long buf_size; > > > int ret; > > > > > > + errno = 0; > > > buf_size = sysconf(_SC_GETPW_R_SIZE_MAX); > > > + if (buf_size < 0 && errno == 0) { > > > + buf_size = 2048; > > > + LOG(DEBUG, > > > +"sysconf(_SC_GETPW_R_SIZE_MAX) is not supported, using a buffer size of > > > %ld", "... an initial buffer size of ..." > > > + buf_size); > > > + } > > > if (buf_size < 0) { > > > LOGE(ERROR, "sysconf(_SC_GETPW_R_SIZE_MAX) returned error > > > %ld", > > > buf_size); > > > > > > > So on Linux the behavior is somewhat similar [1]. But I took a peek at > > the libvirt code for doing the similar thing and I notice that they > > just > > default if the value is returned as less than 0 [2]. Reading both man > > pages it seems like that would be the better bet instead of failing how > > the current code is. Your fix probably makes it fail less but it could > > still error out senselessly. Just a suggestion for an improvement > > overall. > > Ack, it doesn't make much sense to error out if we cannot find an > initial value for the buffer, the code below is able to adapt and expand > the buffer as needed anyway. I'm going to resend with that fixed. Sounds good. Don't forget to CC all the tools maintainers next time. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
