Some long diatribe about my battered-wife syndrome with C

_posts/2011-05-20-playing-with-pointers-and-fire.markdown

@@ -0,0 +1,98 @@
+---
+layout: post
+title: Playing with pointers, and fire
+tags:
+- software development
+- lookout
+- c
+- ada
+---
+
+
+It is a little (unknown) fact that my first job as a software developer was
+writing C code, for the [network group](http://nis.tamu.edu/) at [Texas A&M
+University](http://www.tamu.edu). Like most student developers, my work never
+saw the light of day, mostly because I never finished it, but I did learn an
+incredible amount working on my little project made for one.
+
+I had never expected that 6 years later in my career, I'd somehow still be
+dealing with some of the same issues, in the same crusty 30 year old language:
+C. I feel I should note that every job that I've ever had, except *one*,
+involved writing C code at some point, odd.
+
+<img src="/images/kitty_failure.jpg" alt="Lolcat smashes heap" title="Lolcat
+smashes heap" align="right" width="170"/>
+To be honest I'm both surprised and irritated by C's longevity as a systems
+language.  When I scan the landscape for the titans of modern web software I
+see it *everywhere*. [Redis](http://www.redis.io),
+[Nginx](http://www.nginx.org), [Python](http://www.python.org),
+[Ruby](http://www.ruby-lang.org), [MySQL](http://dev.mysql.com),
+[Apache](http://httpd.apache.org), [HAProxy](http://haproxy.1wt.eu/) and the
+list goes on and on. Don't get me wrong, C is a very fast and suitable tool to
+build all these services, it's just so damn ***dangerous*** that I'm shocked
+how much it's still used.
+
+My mind immediately goes to [this
+study](http://archive.adaic.com/intro/ada-vs-c/cada_art.html) that I had read
+at some point regarding comparisons of development costs and defect rates
+between *very* similar C and Ada projects. While the study is almost as old as
+I am, it strikes a chord with me every time I am working on some C-based
+projects.
+
+Take [this code](https://github.com/antirez/redis/blob/unstable/src/sds.c) from
+the Redis code base for
+example, which I recently had the pleasure of working with. I am aware that
+[Salvatore](https://github.com/antirez) is a brilliant hacker but this is
+*madness*. If you cannot easily grok the code, I'll clarify what this tiny
+library does: in order to provide dynamically sizable strings in C, this code
+will allocate a block of memory for a string that looks like this:
+
+    0               9           N
+    +---------------------------+
+    | struct sdshdr |  char *   |
+    +---------------------------+
+
+A little goofy, but easy to understand and deal with. *Except* for the fact that
+the pointer that is passed around is to address `9` instead of `0`, meaning all
+operations that work with the entire block perform pointer arithmetic to
+calculate the appropriate starting address for the block. For example, here's
+the `sdsfree` implementation:
+
+{% highlight c %}
+   void sdsfree(sds s) { /* sds == char * */
+        free(s - sizeof(struct sdshdr));
+   }
+{% endhighlight %}
+
+I have two reasons for picking on this specific code, and they were both in the
+form of gnarly core dumps I've spent resolving the past couple days. If at
+**any point** in your program you or anybody else accidentally passes a `char*`
+into *any* of these SDS functions, your program will crash and there's nothing
+your compiler can do to save you from this. Since the `sds` is a `typedef` of
+`char*` not only will you never see any compiler warnings, you won't see any
+warnings from static analysis tools either.
+
+
+I've heard people say that one of the problems with C++ is that it gives you
+too much rope with which to hang yourself. If that's the case, C not only gives
+the the rope but double-dog dares you to try to hang yourself with it.
+
+Perhaps in another post I'll detail how pointers and types are handled in Ada,
+which I think is a major improvement of the C model without sacrificing speed.
+I don't mean to imply that everything that is written in C should *really* be
+written in Ada, I just find the language's solution to this problem to be
+interesting. Instead of Ada, pick Java, Python, Scala, Ruby, D or any other
+language that's been developed in the post-K&R world, they all have built on
+top of the lessons learned from C's short-comings.
+
+It's been almost 40 years since C was first introduced; that's over two or three
+generations of programmers hanging themselves.
+
+
+---
+*Disclaimer:* I actually *like* working on projects in C, it's always an
+interesting challenge, like starting arguments with my wife I have no chance of
+winning.
+
+---
+