[Libguestfs] [nbdkit PATCH v2] plugin: add and use nbdkit_realpath

[Pino Toscano]

On Wednesday, 14 February 2018 18:06:10 CET Eric Blake wrote:
> On 02/14/2018 10:53 AM, Pino Toscano wrote:
> > Introduce a new helper function to resolve a path name, calling
> > nbdkit_error on failure: other than doing what nbdkit_absolute_path
> > does, it also checks that the file exists (and thus avoids errors later
> > on).  To help distinguish it from nbdkit_absolute_path, improve the
> > documentation of the latter.
> > 
> > Apply it where an existing path is required, both in nbdkit itself and
> > in plugins.
> > 
> > Related to: https://bugzilla.redhat.com/show_bug.cgi?id=1527334
> > ---
> 
> > +++ b/src/utils.c
> > @@ -228,3 +228,22 @@ nbdkit_read_password (const char *value, char **password)
> >   
> >     return 0;
> >   }
> > +
> > +char *
> > +nbdkit_realpath (const char *path)
> > +{
> > +  char *ret;
> > +
> > +  if (path == NULL || *path == '\0') {
> > +    nbdkit_error ("cannot resolve a null or empty path");
> > +    return NULL;
> > +  }
> > +
> > +  ret = realpath (path, NULL);
> 
> Wait. Does this even work?

It works in the same way as nbdkit_absolute_path() did: when calling it
on a relative path, nbdkit_absolute_path() will prepend $PWD to it,
while the new nbdkit_realpath() will do something similar.

At least the usages that I changed are called before start_serving()
(and thus before fork_into_background()), so I think there should be no
issue wrt paths.

Did I miss anything?

-- 
Pino Toscano
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