FAQ
I have a c program that I want to replace with a python script.

But I don't know c all that well. What I'd like to is look at a visual map
of the c program, a flowchart that draws that subroutines as blocks, points
out what variables traverse the blocks, and highlights external traffic to
sockets and ports.

A basic google search comes up empty, in spite of the fact that I'm not the
first to want such a thing. Thinkgeek offers a linux kernel map poster that
was generated by perl scripts.

So I guess that means roll my own, which means building a c interpreter, by
which time I'll have relearnt enough c to read the code in the first place,
but producing code is much cooler than simply reading code.

So, does anybody have any hints or pointers to hints that would help on this
mad errand?

Thanks
Bruce

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  • John Thingstad at Dec 20, 2002 at 4:44 pm
    My advice. Don't
    The reason no such utillity exists is because it is damn near impossible to
    create such a mapping.
    The C language is a context free grammar (LR(1)) while a flow chart is a
    regular grammar.
    The grammars that can be expessed by a context free grammar are a superset
    of the grammars that can be expessed be a regular grammar.
    This means there is no general mapping from one to the other. The other way
    from flow chart to C works fine.
    Altso forget translating C into python.
    Instead figure out what the program does.
    Write a spec of behaviour and write the python program from scratch using
    this.
    On Fri, 20 Dec 2002 04:50:57 -0500, noc wrote:

    I have a c program that I want to replace with a python script.

    So I guess that means roll my own, which means building a c interpreter,
    by
    which time I'll have relearnt enough c to read the code in the first
    place,
    but producing code is much cooler than simply reading code.

    So, does anybody have any hints or pointers to hints that would help on
    this
    mad errand?

    Thanks
    Bruce

    John Thingstad
  • Simon Burton at Dec 23, 2002 at 2:50 am

    On Fri, 20 Dec 2002 04:50:57 +0000, noc wrote:

    I have a c program that I want to replace with a python script.

    But I don't know c all that well. What I'd like to is look at a visual map
    of the c program, a flowchart that draws that subroutines as blocks, points
    out what variables traverse the blocks, and highlights external traffic to
    sockets and ports.

    A basic google search comes up empty, in spite of the fact that I'm not the
    first to want such a thing. Thinkgeek offers a linux kernel map poster that
    was generated by perl scripts.

    So I guess that means roll my own, which means building a c interpreter, by
    which time I'll have relearnt enough c to read the code in the first place,
    but producing code is much cooler than simply reading code.

    So, does anybody have any hints or pointers to hints that would help on this
    mad errand?

    Thanks
    Bruce
    I am working on a c code parser written in python right now.
    My main focus is parsing .h files to generate wrapper code for python
    (yes i know about SWIG), but i hope it will do a lot more, such
    as general "explaining" that you (and many others) would like.

    highlighting external traffic to sockets is somewhat specific,
    but my hope is that a well written python c-parser will allow for
    custom extensions without to much hassle.

    let me know if you're interested; i'll announce something on c.l.py
    soon i hope,

    cheerioh,

    Simon Burton
    http://arrowtheory.com
  • Bengt Richter at Dec 23, 2002 at 3:57 am

    On Mon, 23 Dec 2002 13:50:55 +1100, "Simon Burton" wrote:
    On Fri, 20 Dec 2002 04:50:57 +0000, noc wrote:

    I have a c program that I want to replace with a python script.

    But I don't know c all that well. What I'd like to is look at a visual map
    of the c program, a flowchart that draws that subroutines as blocks, points
    out what variables traverse the blocks, and highlights external traffic to
    sockets and ports.

    A basic google search comes up empty, in spite of the fact that I'm not the
    first to want such a thing. Thinkgeek offers a linux kernel map poster that
    was generated by perl scripts.

    So I guess that means roll my own, which means building a c interpreter, by
    which time I'll have relearnt enough c to read the code in the first place,
    but producing code is much cooler than simply reading code.

    So, does anybody have any hints or pointers to hints that would help on this
    mad errand?

    Thanks
    Bruce
    I am working on a c code parser written in python right now.
    My main focus is parsing .h files to generate wrapper code for python
    (yes i know about SWIG), but i hope it will do a lot more, such
    as general "explaining" that you (and many others) would like.

    highlighting external traffic to sockets is somewhat specific,
    but my hope is that a well written python c-parser will allow for
    custom extensions without to much hassle.

    let me know if you're interested; i'll announce something on c.l.py
    soon i hope,
    Are you doing it based on a Grammar file like Python's

    D:\Python-2.2.2\Grammar\Grammar

    file? Do you know if there are free grammars around that work with the Python stuff?
    Some commercial flex/bison type tools advertise big lists of language grammars,
    but I haven't googled for open source grammars per se. The other obvious question
    is if there's an automated format conversion between the two. Flex by itself can
    handle lots of conditional stuff (I defined a custom HTML parser using it which goes
    pretty quick, being compiled C++ (yes, you can also use C++).

    BTW what is the reference in Python's grammar in the line

    # Commands for Kees Blom's railroad program

    Is that like the diagrams in the old Jensen/Wirth Pascal book? I loved it that
    the whole language was diagrammed on on a couple of pages.

    Regards,
    Bengt Richter
  • Simon Burton at Dec 23, 2002 at 5:21 am

    On Mon, 23 Dec 2002 03:57:19 +0000, Bengt Richter wrote:
    On Mon, 23 Dec 2002 13:50:55 +1100, "Simon Burton" wrote:


    I am working on a c code parser written in python right now.
    My main focus is parsing .h files to generate wrapper code for python
    (yes i know about SWIG), but i hope it will do a lot more, such
    as general "explaining" that you (and many others) would like.

    highlighting external traffic to sockets is somewhat specific,
    but my hope is that a well written python c-parser will allow for
    custom extensions without to much hassle.

    let me know if you're interested; i'll announce something on c.l.py
    soon i hope,
    Are you doing it based on a Grammar file like Python's

    D:\Python-2.2.2\Grammar\Grammar
    No, i'm writing in the style of a "recursive descent" parser;
    rather than bringing the grammar to the fore, the recursive parsing
    mimics the grammar in the (hand coded) control flow. Also i've heard
    that these are faster parsers than the grammar based ones.
    My sarting point has been Peter Van Der Linden, his book "Expert C
    programming", where he explains how to parse c declarations.
    I have also been working with an ANSI c grammar (for bison) i found somewhere,
    it's been helpful, but the grammar allows a lot of weird stuff, like "int
    f()()()();"
    file? Do you know if there are free grammars around that work with the Python stuff?
    Some commercial flex/bison type tools advertise big lists of language grammars,
    but I haven't googled for open source grammars per se. The other obvious question
    is if there's an automated format conversion between the two. Flex by itself can
    handle lots of conditional stuff (I defined a custom HTML parser using it which goes
    pretty quick, being compiled C++ (yes, you can also use C++).

    BTW what is the reference in Python's grammar in the line

    # Commands for Kees Blom's railroad program

    Is that like the diagrams in the old Jensen/Wirth Pascal book? I loved it that
    the whole language was diagrammed on on a couple of pages.

    Regards,
    Bengt Richter
    Some interesting points you raise,

    Simon Burton
    http://arrowtheory.com
  • Dave Kuhlman at Dec 23, 2002 at 4:52 pm
    Simon Burton wrote:

    [snip]

    I'd like to suggest that your header/interface parser generate XML that
    describes the interface. If you do that, others can write processors that
    transform the XML for different purposes, generate wrappers, generate
    documentation, perform code analysis, etc. And, best of all, these tools
    (for transformation, analysis, etc) could be written in Python. By
    generating XML, you are in effect making the output of your parser public.

    You may want to look at the following for inspiration:

    - SWIG generates XML if you use the "-xml" option.

    - http://www.mip.sdu.dk/~fonseca/idl/

    Dave

    I am working on a c code parser written in python right now.
    My main focus is parsing .h files to generate wrapper code for python
    (yes i know about SWIG), but i hope it will do a lot more, such
    as general "explaining" that you (and many others) would like.

    highlighting external traffic to sockets is somewhat specific,
    but my hope is that a well written python c-parser will allow for
    custom extensions without to much hassle.

    let me know if you're interested; i'll announce something on c.l.py
    soon i hope,

    cheerioh,

    Simon Burton
    http://arrowtheory.com
    --
    Dave Kuhlman
    dkuhlman at rexx.com
    http://www.rexx.com/~dkuhlman
  • Mike Meyer at Dec 30, 2002 at 3:27 am

    Dave Kuhlman <dkuhlman at rexx.com> writes:

    By generating XML, you are in effect making the output of your parser public.
    That's a lie propogated by XML proponents and those wishing to claim
    openness for proprietary data formats. It's equivalent to saying that
    by generating ASCII, I'm in effect making the output of the parser
    public.

    XML - and ASCII - attach fixed meanings to various syntactic features
    of the data. Knowing those features is not sufficient to understand or
    process the data intelligently. You have to know the semantic meaning
    of the variables in the fixed syntax before you can do that. You can't
    even decide if a given bit of XML is valid output without having a
    DTD.

    That being said, you can get a lot of good from having parts of the
    syntax fixed to a common standard. For ASCII, you get to use things
    like standardized numeric<->string conversions. For XML, you get
    libraries that will turn the flat XML text into structured objects,
    transform the data, and even let you edit it in a user-friendly
    manner. These are all good things, and make XML a good choice over a
    proprietary format if all other things are equal.

    <mike
    --
    Mike Meyer <mwm at mired.org> http://www.mired.org/home/mwm/
    Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.
  • Ira Baxter at Dec 30, 2002 at 4:14 pm
    The DMS Software Reengineering Toolkit can be used
    to automate conversions, although this one could
    be pretty hard. It can be obtained with a full
    ANSI C front end having name and type resolution,
    which can answer the questions of what variables
    are used where. "What variables traverse blocks"
    is a dataflow question, and requires pretty serious
    dataflow infrastructure to answer "easily".
    Alas, we aren't quite that far along, so getting
    this information is possible but not fun.

    I will say that starting from scratch to build
    the entire infrastructure you need for processing
    C might sound like fun, but it will take you
    a lot more effort than you think.
    [Yes, I'm biased, but that comes from way
    too much experience doing this kind of thing].
    This is why we offer a commercial product;
    it allows us to distribute the engineering cost
    across a lot of customers.

    See http://www.semdesigns.com/Products/DMS/DMSToolkit.html.

    --
    Ira D. Baxter, Ph.D., CTO 512-250-1018
    Semantic Designs, Inc. www.semdesigns.com

    "Simon Burton" <simonb at webone.com.au> wrote in message
    news:pan.2002.12.23.02.50.50.847704 at webone.com.au...
    On Fri, 20 Dec 2002 04:50:57 +0000, noc wrote:

    I have a c program that I want to replace with a python script.

    But I don't know c all that well. What I'd like to is look at a visual
    map
    of the c program, a flowchart that draws that subroutines as blocks,
    points
    out what variables traverse the blocks, and highlights external traffic
    to
    sockets and ports.

    A basic google search comes up empty, in spite of the fact that I'm not
    the
    first to want such a thing. Thinkgeek offers a linux kernel map poster
    that
    was generated by perl scripts.

    So I guess that means roll my own, which means building a c interpreter,
    by
    which time I'll have relearnt enough c to read the code in the first
    place,
    but producing code is much cooler than simply reading code.

    So, does anybody have any hints or pointers to hints that would help on
    this
    mad errand?

    Thanks
    Bruce
    I am working on a c code parser written in python right now.
    My main focus is parsing .h files to generate wrapper code for python
    (yes i know about SWIG), but i hope it will do a lot more, such
    as general "explaining" that you (and many others) would like.

    highlighting external traffic to sockets is somewhat specific,
    but my hope is that a well written python c-parser will allow for
    custom extensions without to much hassle.

    let me know if you're interested; i'll announce something on c.l.py
    soon i hope,

    cheerioh,

    Simon Burton
    http://arrowtheory.com

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postedDec 20, '02 at 9:50a
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