[U-Boot] [PATCH] tools/genboardscfg.py: Don't rely on subprocess.check_output

[Tom Rini]

On Wed, Jul 30, 2014 at 02:04:50PM -0400, Tom Rini wrote:
> On Thu, Jul 31, 2014 at 02:54:43AM +0900, Masahiro YAMADA wrote:
> > Hi Tom,
> > 
> > 
> > 2014-07-30 23:24 GMT+09:00 Tom Rini <trini at ti.com>:
> > >
> > > The function subprocess.check_output() only exists in Python 2.7 and
> > > later (and there are long term supported distributions that ship with
> > > 2.6.x).  Replace this with a call to subprocess.Popen() and then checking
> > > output via communicate()
> > 
> > Unfortunately..  :-(
> > Anyway, thanks for catching this issue.
> > 
> > 
> > > Signed-off-by: Tom Rini <trini at ti.com>
> > > ---
> > >  tools/genboardscfg.py |    9 ++++++---
> > >  1 files changed, 6 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/tools/genboardscfg.py b/tools/genboardscfg.py
> > > index 805e4eb..6588392 100755
> > > --- a/tools/genboardscfg.py
> > > +++ b/tools/genboardscfg.py
> > > @@ -83,7 +83,8 @@ def check_top_directory():
> > >  def get_make_cmd():
> > >      """Get the command name of GNU Make."""
> > >      try:
> > > -        make_cmd = subprocess.check_output([SHOW_GNU_MAKE])
> > > +        process = subprocess.Popen([SHOW_GNU_MAKE], stdout=subprocess.PIPE)
> > > +        make_cmd, unused = process.communicate()
> > >      except subprocess.CalledProcessError:
> > >          print >> sys.stderr, 'GNU Make not found'
> > >          sys.exit(1)
> > 
> > 
> > 
> > No good.
> > 
> > Unlike check_output(),  the communicate() method never throws
> > CalledProcessError exception,
> > which means the lines in except are never run.
> > 
> > When scripts/show-gnu-make fails, the function will not error out, but
> > just return a null string.
> > To know if the subprocess succeeded or not, 'returncode' should be checked.
> > 
> > 
> > The correct code should be something like this:
> > 
> > 
> > def get_make_cmd():
> >     """Get the command name of GNU Make."""
> >     process = subprocess.Popen([SHOW_GNU_MAKE], stdout=subprocess.PIPE)
> >     ret = process.communicate()
> >     if process.returncode:
> >         print >> sys.stderr, 'GNU Make not found'
> >         sys.exit(1)
> >     return ret[0].strip()
> > 
> > 
> > 
> > >
> > > @@ -493,8 +494,10 @@ def main():
> > >              sys.exit(1)
> > >      else:
> > >          try:
> > > -            jobs = int(subprocess.check_output(['getconf',
> > > -                                                '_NPROCESSORS_ONLN']))
> > > +            process = subprocess.Popen(['getconf', '_NPROCESSORS_ONLN'],
> > > +                                       stdout=subprocess.PIPE)
> > > +            jobstr, unused = process.communicate()
> > > +            jobs = int(jobstr)
> > >          except subprocess.CalledProcessError:
> > >              print 'info: failed to get the number of CPUs. Set jobs to 1'
> > >              jobs = 1
> > > --
> > 
> > Ditto.
> > 'except subprocess.CalledProcessError:' is meaningless and never
> > catches an exception.
> > 
> > In this case, 'getconf' may not exist on some systems.
> > 
> > If the 'getconf' command is not found, Popen() will throw OSError exception.
> > If the command is found but fails by some reason, int() will throw ValueError.
> > We cannot handle the other exceptions.
> > 
> > So, we can write the code something like this:
> > 
> >  ...
> >     else:
> >         try:
> >             jobs = int(subprocess.Popen(['getconf', '_NPROCESSORS_ONLN'],
> >                                      stdout=subprocess.PIPE).communicate()[0])
> >         except (OSError, ValueError):
> >             # getconf command not found or fails
> >             print 'info: failed to get the number of CPUs. Set jobs to 1'
> >             jobs = 1
> >     gen_boards_cfg(jobs)
> 
> Arg.  Do you want me to fold / rework things like that or do you want to
> post a v9 of just this patch, adapted as you've shown?

... doing it this way now, testing, will move from there :)

-- 
Tom
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