Re: [libvirt] FreeBSD and sysconf(_SC_GETPW_R_SIZE_MAX)
On 05/16/2011 03:27 AM, Daniel P. Berrange wrote:
On Sun, May 15, 2011 at 07:22:46AM +0200, Matthias Bolte wrote:
> On FreeBSD virsh fails to enter interactive mode because
> vshReadlineInit fails, because virGetUserDirectory fails, because
> virGetUserEnt fails, because sysconf(_SC_GETPW_R_SIZE_MAX) returns -1
> and sets errno to EINVAL.
>
> Is this something that gnulib should/could deal with, Eric?
sysconf() is a can of worms; no chance that gnulib will touch it any
time soon.
>
> Or should we work around it in libvrt and fallback to PATH_MAX when
> sysconf(_SC_GETPW_R_SIZE_MAX) fails?
PATH_MAX isn't expected to be available on all platforms either which
is one of the reasons for us removing its use.
getpwnam() returns ERANGE if the allocated buffer is too small. So
we should do something along the lines of
size_t len = sysconf(_SC_GETPW_R_SIZE_MAX)
Guarded by #ifdef, and defaulting to -1 if _SC_GETPW_R_SIZE_MAX is not
defined (since it is a handy extension, but not present everywhere).
if (len < 0)
len = 1024;
while (1) {
...
err = getpwnam()
if (err < 0) {
if (errno == ERANGE) {
len += 1024;
Or len <<= 1, to avoid quadratic performance.
But indeed this is the correct response.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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