| Andrew Cooke | Contents | Latest | RSS | Twitter | Previous | Next

C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

Last 100 entries

ASCII Fluid Dynamics; Brandalism; Table of Shifter, Cassette and Derailleur Compatability; Lenovo Demonstrates How Bad HTTPS Is; Telegraph Owned by HSBC; Smaptop - Sunrise (Music); Equation Group (NSA); UK Torture in NI; And - A Natural Extension To Regexps; This Is The Future Of Religion; The Shazam (Music Matching) Algorithm; Tributes To Lesbian Community From AIDS Survivors; Nice Rust Summary; List of Good Fiction Books; Constructing JSON From Postgres (Part 2); Constructing JSON From Postgres (Part 1); Postgres in Docker; Why Poor Places Are More Diverse; Smart Writing on Graceland; Satire in France; Free Speech in France; MTB Cornering - Where Should We Point Our Thrusters?; Secure Secure Shell; Java Generics over Primitives; 2014 (Charlie Brooker); How I am 7; Neural Nets Applied to Go; Programming, Business, Social Contracts; Distributed Systems for Fun and Profit; XML and Scheme; Internet Radio Stations (Curated List); Solid Data About Placebos; Half of Americans Think Climate Change Is a Sign of the Apocalypse; Saturday Surf Sessions With Juvenile Delinquents; Ssh, tty, stdout and stderr; Feathers falling in a vacuum; Santiago 30m Bike Route; Mapa de Ciclovias en Santiago; How Unreliable is UDP?; SE Santiago 20m Bike Route; Cameron's Rap; Configuring libxml with Eclipse; Reducing Combinatorial Complexity With Occam - AI; Sentidos Comunes (Chilean Online Magazine); Hilary Mantel: The Assassination of Margaret Thatcher - August 6th 1983; NSA Interceptng Gmail During Delivery; General IIR Filters; What's happening with Scala?; Interesting (But Largely Illegible) Typeface; Retiring Essentialism; Poorest in UK, Poorest in N Europe; I Want To Be A Redneck!; Reverse Racism; The Lost Art Of Nomography; IBM Data Center (Photo); Interesting Account Of Gamma Hack; The Most Interesting Audiophile In The World; How did the first world war actually end?; Ky - Restaurant Santiago; The Black Dork Lives!; The UN Requires Unaninmous Decisions; LPIR - Steganography in Practice; How I Am 6; Clear Explanation of Verizon / Level 3 / Netflix; Teenage Girls; Formalising NSA Attacks; Switching Brakes (Tektro Hydraulic); Naim NAP 100 (Power Amp); AKG 550 First Impressions; Facebook manipulates emotions (no really); Map Reduce "No Longer Used" At Google; Removing RAID metadata; New Bike (Good Bike Shop, Santiago Chile); Removing APE Tags in Linux; Compiling Python 3.0 With GCC 4.8; Maven is Amazing; Generating Docs from a GitHub Wiki; Modular Shelves; Bash Best Practices; Good Emergency Gasfiter (Santiago, Chile); Readings in Recent Architecture; Roger Casement; Integrated Information Theory (Or Not); Possibly undefined macro AC_ENABLE_SHARED; Update on Charges; Sunburst Visualisation; Spectral Embeddings (Distances -> Coordinates); Introduction to Causality; Filtering To Help Colour-Blindness; ASUS 1015E-DS02 Too; Ready Player One; Writing Clear, Fast Julia Code; List of LatAm Novels; Running (for women); Building a Jenkins Plugin and a Jar (for Command Line use); Headphone Test Recordings; Causal Consistency; The Quest for Randomness; Chat Wars; Real-life Financial Co Without ACID Database...; Flexible Muscle-Based Locomotion for Bipedal Creatures

© 2006-2013 Andrew Cooke (site) / post authors (content).

Coding Guidelines for C

From: andrew cooke <andrew@...>

Date: Mon, 20 Jun 2011 10:29:38 -0400

I've been back coding in C for a while and want to record some simple rules
that make programs simpler:

1 - Always return a status.  Non-zero is an error.  Always check status on
    return.  On error, goto exit for cleanup.

    So functions should look like:

    int myfunction(blah blah) {
      char *text = NULL;
      void *point = NULL;
      int status = 0;
      ...
      if ((status = otherfunction(args here))) goto exit;
      if ((status = yetanother(...))) goto exit;
      ...
    exit:
      if (text) free(text);
      if (pointer) free(pointer)
      return status;
    }

2 - Write allocators and destructors for complex data (structs).  These should
    always take a pointer to a pointer and set the pointer to NULL.
    Similarly, use calloc to allocate data so that pointers are NULL from the
    start).  This follows on from the above - using NULL to indicate that data
    are already freed:

    int alloc_foo(foo **my_foo) {
      int status;
      *my_foo = calloc(1, sizeof(foo));
      if (! my_foo) return MEMORY_ERROR;
      (*my_foo)->counts = calloc(1, 20 * sizeof(int));
      if (! (*my_foo)->counts) return MEMORY_ERROR;
      if ((status = alloc_inner(&(*my_foo)->inner))) return status
      return 0;
    }

    int free_foo(foo **my_foo, status) {
      if (*my_foo) {
        if ((*my_foo)->counts) free((*my_foo)->counts);
        (*my_foo)->counts = NULL;
	status = free_inner(&(*my_foo)->inner, status)
        *my_foo = NULL;
      }
      return status;
    }

3 - Cleanup functions should take status an argument and "make it worse".  the
    the idea here is that you want to call cleanup functions even if there are
    errors, but you don't want to "reset" status to OK (zero) if it was bad.
    In the examples above it's not so clear, but consider, say, releasing a
    database:

    int release_db(cnxn *db, int status) {
      db_lib_release(db);
      if (db_lib_error() && ! status) status = DB_ERROR;
      return status;
    }

    This simplifies the "exit:" code and also allows one-liners when you want
    to do one thing with a database and then release it:

      if ((status = release_db(db, do_db_thing(db, ....)))) goto exit;

4 - Use typedefs for structs:

    typedef struct {
      int my_int;
    } my_struct;

5 - Either namespace with names (and use static functions to avoid clutter
    wherever possible) or namespace with "objects":

    typedef struct self {
      ...
      int (*free)(struct self **foo, int status);
    } foo;

Andrew

Comment on this post