[libvirt] [PATCH] docs: ensure outputfile is deleted if rst2html/rst2man fail

[Daniel P. Berrangé]

On Wed, Dec 11, 2019 at 12:52:20PM -0600, Eric Blake wrote:
> On 12/11/19 12:45 PM, Daniel P. Berrangé wrote:
> > This avoids leaving a zero length or partially generated output
> > file on errors.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> > ---
> >   docs/Makefile.am | 10 +++++-----
> >   1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/docs/Makefile.am b/docs/Makefile.am
> > index eb8de80b9c..9a1f7a6117 100644
> > --- a/docs/Makefile.am
> > +++ b/docs/Makefile.am
> > @@ -259,21 +259,21 @@ man8_MANS = $(manpages8_rst:%.rst=%.8)
> >   	   grep -v '^\.\. contents::' < $< | \
> >   	   sed -e 's|SYSCONFDIR|$(sysconfdir)|g' \
> >   	       -e 's|RUNSTATEDIR|$(runstatedir)|g' | \
> > -	   $(RST2MAN) > $@
> > +	   $(RST2MAN) > $@ || { rm $@ && exit 1; }
> 
> But still allows a truncated view of the file if another process accesses
> the file while RST2MAN is still running.  Even better is to generate output
> to a temp file then atomically mv it into place, so that no concurrent
> process can ever see an incomplete file.

Is that a problem that actually impacts negatively in real world for builds?
In various places in the make rules, we've either done the "|| rm" approach,
or the temp file and rename approach. Personally I find the recipes using
the "|| rm" approach are more maintainable/readable.


Regards,
Daniel
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