[Libguestfs] [PATCH nbdkit 1/2] file: Add an internal "mode"

[Richard W.M. Jones]

On Thu, Aug 18, 2022 at 10:27:11AM +0200, Laszlo Ersek wrote:
> On 08/17/22 17:38, Richard W.M. Jones wrote:
> > Previously we relied on the implicit assumption filename xor directory,
> > representing two modes.  Make this explicit with an internal mode
> > variable.
> > 
> > This is just refactoring and should not change the functionality.
> > However we're now more strict about duplicate file= or dir= parameters
> > appearing on the command line.  Previously only the last one had an
> > effect and the others were silently ignored.  Now we give an error in
> > this case.  eg this worked before but now gives an error:
> > 
> >   $ ./nbdkit file /var/tmp /var/tmp/fedora-36.img
> >   nbdkit: error: file|dir parameter can only appear once on the command line
> > ---
> >  plugins/file/file.c | 124 +++++++++++++++++++++++++++-----------------
> >  1 file changed, 76 insertions(+), 48 deletions(-)
> > 
> > diff --git a/plugins/file/file.c b/plugins/file/file.c
> > index aefca9ee2..f673ec132 100644
> > --- a/plugins/file/file.c
> > +++ b/plugins/file/file.c
> > @@ -70,6 +70,7 @@
> >  #include "isaligned.h"
> >  #include "fdatasync.h"
> >  
> > +static enum { mode_none, mode_filename, mode_directory } mode = mode_none;
> >  static char *filename = NULL;
> >  static char *directory = NULL;
> >  
> > @@ -180,14 +181,23 @@ file_config (const char *key, const char *value)
> >     * existence checks to the last possible moment.
> >     */
> >    if (strcmp (key, "file") == 0) {
> > -    free (filename);
> > +    if (mode != mode_none) {
> > +    wrong_mode:
> 
> *shudder*
> 
> please move error handling sections to the end of the function. It's OK
> to jump forward in exceptional cases, but crossing jump lines (i.e.
> improper balancing / nesting) and backward jumps for error handling are
> terrible.

I don't think I really have a problem with it, but I moved it
to the end of the function.

Rich.

-- 
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