Feb. 23, 2011, 1:27 p.m.
posted by psyche
Why Not C?
C is the native language of Unix. Since the early 1980s it has come to dominate systems programming almost everywhere in the computer industry. Outside of Fortran's dwindling niche in scientific and engineering computing, and excluding the vast invisible dark mass of COBOL financial applications at banks and insurance companies, C and its offspring C++ have now (in 2003) dominated applications programming almost completely for more than a decade.
It may therefore seem perverse to assert that C and C++ are nowadays almost always the wrong vehicle for beginning new applications development. But it's true; C and C++ optimize for machine efficiency at the expense of increased implementation and (especially) debugging time. While it still makes sense to write system programs and time-critical kernels of applications in C or C++, the world has changed a great deal since these languages came to prominence in the 1980s. In 2003, processors are a thousand times faster, memories are a thousand times larger, and disks are a factor of ten thousand larger, for roughly constant dollars.
These plunging costs change the economics of programming in a fundamental way. Under most circumstances it no longer makes sense to try to be as sparing of machine resources as C permits. Instead, the economically optimal choice is to minimize debugging time and maximize the long-term maintainability of the code by human beings. Most sorts of implementation (including application prototyping) are therefore better served by the newer generation of interpreted and scripting languages. This transition exactly parallels the conditions that, last time around the wheel, led to the rise of C/C++ and the eclipse of assembler programming.
The central problem of C and C++ is that they require programmers to do their own memory management—to declare variables, to explicitly manage pointer-chained lists, to dimension buffers, to detect or prevent buffer overruns, and to allocate and deallocate dynamic storage. Some of this task can be automated away by unnatural acts like retrofitting C with a garbage collector such as the Boehm-Weiser implementation, but the design of C is such that this cannot be a complete solution.
C memory management is an enormous source of complication and error. One study (cited in [Boehm]) estimates that 30% or 40% of development time is devoted to storage management for programs that manipulate complex data structures. This did not even include the impact on debugging cost. While hard figures are lacking, many experienced programmers believe that memory-management bugs are the single largest source of persistent errors in real-world code. Buffer overruns are a common cause of crashes and security holes. Dynamic-memory management is particularly notorious for spawning insidious and hard-to-track bugs, such as memory leaks and stale-pointer problems.
Not so long ago, manual memory management made sense anyway. But there are no 'small systems' any more, not in mainstream applications programming. Under today's conditions, an implementation language that automates away memory management (and buys an order of magnitude decrease in bugs at the expense of using a bit more cycles and core) makes a lot more sense.
A recent paper [Prechelt] musters an impressive array of statistical evidence for a claim that programmers with experience in both worlds will find very plausible: programmers are just about twice as productive in scripting languages as they are in C or C++. This accords well with the 30%–40% penalty estimate noted earlier, plus debugging overhead. The performance penalty of using a scripting language is very often insignificant for real-world programs, because real-world programs tend to be limited by waits for I/O events, network latency, and cache-line fills rather than by the efficiency with which they use the CPU itself.
The Unix world has been slowly coming around to this point of view in practice, especially since 1990 or so, as is shown by the increasing popularity of Perl and other scripting languages. But the evolution of practice has not yet (as of mid-2003) led to a wholesale change in conscious attitudes; many Unix programmers are still absorbing the lesson Perl and Python have been teaching.
We can see the same trend happening, albeit more slowly, outside the Unix world—for example, in the continuing shift from C++ to Visual Basic evident in applications development under Microsoft Windows and NT, and the move toward Java in the mainframe world.
The arguments against C and C++ apply with equal force to other conventional compiled languages such as Pascal, Algol, PL/I, FORTRAN, and compiled Basic dialects. Despite occasional heroic efforts such as Ada, the differences between conventional languages remain superficial when set against their basic design decision to leave memory management to the programmer. Though high-quality open-source implementations of most languages ever written are available under Unix, no other conventional languages remain in widespread use in the Unix or Windows worlds; they have been abandoned in favor of C and C++. Accordingly we will not survey them here.