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

[Tom Rini]

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?

-- 
Tom
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