Re: [Qemu-devel] [PATCH v2 2/2] qapi: add a special string in c_type()'s result to each redundant space

[Amos Kong]

On Fri, Apr 25, 2014 at 02:52:09PM +0200, Markus Armbruster wrote:
> Amos Kong <address@hidden> writes:

Hi Markus,
 
> > Currently we always add a space after c_type in mcgen(), there is
> > some redundant space in generated code. The space isn't needed for
> > points by the coding style.
> 
> You mean pointers.
> 
> >
> >   char * value;
> >         ^
> >   qapi_free_NameInfo(NameInfo * obj)
> >                                ^
> >
> > This patch added a special string 'EATSPACE' in the end of c_type()'s
> > result only for point type. The string and the following space will be
> > striped in mcgen().
> 
> Suggest:
> 
>     qapi: Suppress unwanted space between type and identifier
> 
>     We always generate a space between type and identifier in parameter
>     and variable declarations, even when idiomatic C style doesn't have
>     a space there.  Suppress it.
> 
> This explains what you do and why, but not how.  A commit message should
> always cover "what" and "why", but "how" can be ommitted in simple cases
> like this one.
> 
> Use of "EATSPACE" as marker is unnecessarily fragile, as it could
> legitimately occur in generated code.  Recommend to pick something that
> can't, such as "\033EATSPACE."

"\033EATSPACE." works, I will use it.
 
> > Signed-off-by: Amos Kong <address@hidden>
> > ---
> >  scripts/qapi-commands.py |  2 +-
> >  scripts/qapi.py          | 11 ++++++-----
> >  2 files changed, 7 insertions(+), 6 deletions(-)
> >
> > diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
> > index 9734ab0..0ebb1b9 100644
> > --- a/scripts/qapi-commands.py
> > +++ b/scripts/qapi-commands.py
> > @@ -26,7 +26,7 @@ def type_visitor(name):
> >  def generate_command_decl(name, args, ret_type):
> >      arglist=""
> >      for argname, argtype, optional, structured in parse_args(args):
> > -        argtype = c_type(argtype)
> > +        argtype = c_type(argtype).replace('EATSPACE', '')
> >          if argtype == "char *":
> >              argtype = "const char *"
> >          if optional:
> 
> Ugly, and you make it uglier :)

It's not just ugly, eatspace string is cleaned, so the space can be
eaten.
 
> Two cleaner alternatives:
> 
> * Test argname instead.  Still ugly, but less so.
> 
> * Make c_type() take optional parameter is_param, and have it add const
>   when true.

I will add a parameter to only add 'const ' prefix for str type.
 
> > diff --git a/scripts/qapi.py b/scripts/qapi.py
> > index b474c39..b46c518 100644
> > --- a/scripts/qapi.py
> > +++ b/scripts/qapi.py
> > @@ -423,7 +423,7 @@ def is_enum(name):
> >  
> >  def c_type(name):
> >      if name == 'str':
> > -        return 'char *'
> > +        return 'char *EATSPACE'
> >      elif name == 'int':
> >          return 'int64_t'
> >      elif (name == 'int8' or name == 'int16' or name == 'int32' or
> > @@ -437,15 +437,15 @@ def c_type(name):
> >      elif name == 'number':
> >          return 'double'
> >      elif type(name) == list:
> > -        return '%s *' % c_list_type(name[0])
> > +        return '%s *EATSPACE' % c_list_type(name[0])
> >      elif is_enum(name):
> >          return name
> >      elif name == None or len(name) == 0:
> >          return 'void'
> >      elif name == name.upper():
> > -        return '%sEvent *' % camel_case(name)
> > +        return '%sEvent *EATSPACE' % camel_case(name)
> >      else:
> > -        return '%s *' % name
> > +        return '%s *EATSPACE' % name
> >  
> >  def genindent(count):
> >      ret = ""
> 
> Please define a global constant instead of repeating your magic string
> over and over.
> 
> > @@ -470,7 +470,8 @@ def cgen(code, **kwds):
> >      return '\n'.join(lines) % kwds + '\n'
> >  
> >  def mcgen(code, **kwds):
> > -    return cgen('\n'.join(code.split('\n')[1:-1]), **kwds)
> > +    raw = cgen('\n'.join(code.split('\n')[1:-1]), **kwds)
> > +    return raw.replace('*EATSPACE ', '*')
> >  
> >  def basename(filename):
> >      return filename.split("/")[-1]
> 
> This makes EATSPACE work only after '*'.  You never emit it anywhere
> else, but relying on it here isn't necessary.  I'd do something like
> 
>     return re.sub(re.escape(eatspace) + ' +', '', raw)

OK
Thanks.

-- 
                        Amos.