help with pretty printing

help with pretty printing

[somersetgraham]

I am writing some gdb pretty printers for Qt classes to be used in the
Eclipse IDE, but cannot seem to handle pointers to data structures very well
(I am very new to Python)

For example I want to pretty print the QFile structure which I have achieved
with following code –

class QFilePrinter:
    def __init__(self, val):
        self.val = val
        data = self.val['d_ptr']['d'].dereference()

    def children(self):
        names = [1,2]
        data = self.val['d_ptr']['d']
        for i in names:
            if i==1:
                ptype = gdb.lookup_type("QFilePrivate").pointer()
                yield "fileName",data.cast(ptype).dereference()["fileName"]
            if i == 2:
                exp = "((class QFile*)%s)->exists()" % (self.val.address)
                r = callClassMethod(self.val, "exists","")
                yield "exists",r
                    
    def to_string (self):
        data = self.val['d_ptr']['d']
        ptype = gdb.lookup_type("QFilePrivate").pointer()
        return "%s %s" %
("fileName",data.cast(ptype).dereference()["fileName"])

    def display_hint (self):
        return 'string'

I have followed some examples that I found online  for building a lookup
table functions to be called – 

def lookup_function (val):
    #print "Look-up and return a pretty-printer that can print val."

    # Get the type.
    type = val.type;
    print type
    # If it points to a reference, get the reference.
    if type.code == gdb.TYPE_CODE_REF:
        print "deref"
        type = type.target ()

    print type
    # Get the unqualified type, stripped of typedefs.
    type = type.unqualified ().strip_typedefs ()
    print type
       
    # Get the type name.
    typename = type.tag
    print typename
    #print typename
    if typename == None:
        print "None"
        return None

    # Iterate over local dictionary of types to determine
    # if a printer is registered for that type.  Return an
    # instantiation of the printer if found.
    for function in pretty_printers_dict:
        if function.search (typename):
            print "found"
            return pretty_printers_dict[function] (val)
                    
    # Cannot find a pretty printer.  Return None.
    print "not found"
    return None
#
def build_dictionary ():
    pretty_printers_dict[re.compile ('^QFile$')] = lambda
val:QFilePrinter(val)
    pretty_printers_dict[re.compile ('^QFile *$')] = lambda
val:QFilePrinter(val)

pretty_printers_dict = {}

build_dictionary ()

When I debug my code containing a pointer to a QFile object my pretty
printer is not invoked, but if I type ‘print *f’ (f is a pointer to a QFile
object) the pretty printer is invoked. Also I add ‘*f’ in the Expressions
window in Eclipse the printer is invoked.

Is it possible to get my pretty printer to work with pointers in all cases?


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Re: help with pretty printing

[Niko Sams]

On Fri, Jun 1, 2012 at 11:07 AM, somersetgraham
<graham.labdon@avalonsciences.com> wrote:
>
> I am writing some gdb pretty printers for Qt classes to be used in the
> Eclipse IDE, but cannot seem to handle pointers to data structures very well
> (I am very new to Python)
No answer to your question, but did you consider contributing your
pretty printers to kdevelop?

cheers,
Niko

Re: help with pretty printing

[xgsa]

You could try the Qt pretty from here: 
https://projects.kde.org/projects/extragear/kdevelop/kdevelop/repository/revisions/4.1/show/debuggers/gdb/printers

If they work properly you could compare their implementation with yours 
or just use them.

Anton.

-------- Original message --------
> I am writing some gdb pretty printers for Qt classes to be used in the
> Eclipse IDE, but cannot seem to handle pointers to data structures very well
> (I am very new to Python)
>
> For example I want to pretty print the QFile structure which I have achieved
> with following code –
>
> class QFilePrinter:
>      def __init__(self, val):
>          self.val = val
>          data = self.val['d_ptr']['d'].dereference()
>
>      def children(self):
>          names = [1,2]
>          data = self.val['d_ptr']['d']
>          for i in names:
>              if i==1:
>                  ptype = gdb.lookup_type("QFilePrivate").pointer()
>                  yield "fileName",data.cast(ptype).dereference()["fileName"]
>              if i == 2:
>                  exp = "((class QFile*)%s)->exists()" % (self.val.address)
>                  r = callClassMethod(self.val, "exists","")
>                  yield "exists",r
>
>      def to_string (self):
>          data = self.val['d_ptr']['d']
>          ptype = gdb.lookup_type("QFilePrivate").pointer()
>          return "%s %s" %
> ("fileName",data.cast(ptype).dereference()["fileName"])
>
>      def display_hint (self):
>          return 'string'
>
> I have followed some examples that I found online  for building a lookup
> table functions to be called –
>
> def lookup_function (val):
>      #print "Look-up and return a pretty-printer that can print val."
>
>      # Get the type.
>      type = val.type;
>      print type
>      # If it points to a reference, get the reference.
>      if type.code == gdb.TYPE_CODE_REF:
>          print "deref"
>          type = type.target ()
>
>      print type
>      # Get the unqualified type, stripped of typedefs.
>      type = type.unqualified ().strip_typedefs ()
>      print type
>
>      # Get the type name.
>      typename = type.tag
>      print typename
>      #print typename
>      if typename == None:
>          print "None"
>          return None
>
>      # Iterate over local dictionary of types to determine
>      # if a printer is registered for that type.  Return an
>      # instantiation of the printer if found.
>      for function in pretty_printers_dict:
>          if function.search (typename):
>              print "found"
>              return pretty_printers_dict[function] (val)
>
>      # Cannot find a pretty printer.  Return None.
>      print "not found"
>      return None
> #
> def build_dictionary ():
>      pretty_printers_dict[re.compile ('^QFile$')] = lambda
> val:QFilePrinter(val)
>      pretty_printers_dict[re.compile ('^QFile *$')] = lambda
> val:QFilePrinter(val)
>
> pretty_printers_dict = {}
>
> build_dictionary ()
>
> When I debug my code containing a pointer to a QFile object my pretty
> printer is not invoked, but if I type ‘print *f’ (f is a pointer to a QFile
> object) the pretty printer is invoked. Also I add ‘*f’ in the Expressions
> window in Eclipse the printer is invoked.
>
> Is it possible to get my pretty printer to work with pointers in all cases?
>
>

Re: help with pretty printing

[Niko Sams]

On Sat, Jun 2, 2012 at 12:28 PM, xgsa <xgsa@yandex.ru> wrote:
> You could try the Qt pretty from here:
> https://projects.kde.org/projects/extragear/kdevelop/kdevelop/repository/revisions/4.1/show/debuggers/gdb/printers
>
> If they work properly you could compare their implementation with yours or
> just use them.
I've written those :D
I'm just asking graham if he want's to add his QFilePrinter there (and
possibly others)

Niko

Re: help with pretty printing

[xgsa]

> On Sat, Jun 2, 2012 at 12:28 PM, xgsa<xgsa@yandex.ru>  wrote:
>> You could try the Qt pretty from here:
>> https://projects.kde.org/projects/extragear/kdevelop/kdevelop/repository/revisions/4.1/show/debuggers/gdb/printers
>>
>> If they work properly you could compare their implementation with yours or
>> just use them.
> I've written those :D

Ok, so taking the opportunity I want to thank you. I use them and they 
are cool! :)

> I'm just asking graham if he want's to add his QFilePrinter there (and
> possibly others)

I thought it is supported yet. Yes, it would be great to add it.


Anton.

Re: help with pretty printing

[Joachim Protze]

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On 01.06.2012 11:07, somersetgraham wrote:
> def build_dictionary ():
>     pretty_printers_dict[re.compile ('^QFile$')] = lambda
> val:QFilePrinter(val)
>     pretty_printers_dict[re.compile ('^QFile *$')] = lambda
> val:QFilePrinter(val)
you may try something like the following to match both cases:

pretty_printers_dict[re.compile('^QFile ( \*)?$')] = lambda
val:QFilePrinter(val)


The asterisk is a special character in regular expressions and has to be escaped to match an asterisk. Your regexp matches QFile with any count of spaces as postfix.

- Joachim



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Re: help with pretty printing

[Paul_Koning]

On Jun 7, 2012, at 3:42 AM, Joachim Protze wrote:

> On 01.06.2012 11:07, somersetgraham wrote:
>> def build_dictionary ():
>>    pretty_printers_dict[re.compile ('^QFile$')] = lambda
>> val:QFilePrinter(val)
>>    pretty_printers_dict[re.compile ('^QFile *$')] = lambda
>> val:QFilePrinter(val)
> you may try something like the following to match both cases:
> 
> pretty_printers_dict[re.compile('^QFile ( \*)?$')] = lambda
> val:QFilePrinter(val)
> 
> 
> The asterisk is a special character in regular expressions and has to be escaped to match an asterisk. Your regexp matches QFile with any count of spaces as postfix.
> 
> - Joachim

Yes, but since you're dealing with a regular (not raw) string here, the \ needs to be doubled, otherwise it is treated as a string character escape instead of a backslash character inside the string.  So one of these will match space followed by asterisk:

pretty_printers_dict[re.compile('^QFile ( \\*)?$')] = lambda val:QFilePrinter(val)
pretty_printers_dict[re.compile(r'^QFile ( \*)?$')] = lambda val:QFilePrinter(val)

Re: help with pretty printing

[Joachim Protze]

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Hi,
On 07.06.2012 20:26, Paul_Koning@Dell.com wrote:
> Yes, but since you're dealing with a regular (not raw) string here, the \ needs to be doubled, otherwise it is treated as a string character escape instead of a backslash character inside the string.  So one of these will match space followed by asterisk:
your post let me wonder, why my code worked for me and I asked the
python interpreter for his opinion:

>>> '^QFile (
\*)?$'                                                                                                                       

'^QFile (
\\*)?$'                                                                                                                          

>>> '^QFile (
\\*)?$'                                                                                                                      

'^QFile (
\\*)?$'                                                                                                                          

>>> r'^QFile (
\*)?$'                                                                                                                      

'^QFile ( \\*)?$'

Equal output for all versions of these strings and for python versions
2.4, 2.6, 2.7 and 3.2 (the versions I found on severals machines).

- Joachim



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