I agree with essentially everything in wglb's message, but (once again) I'll grumpily jump in to emphasize a point which I think many on this list have missed.

On Fri, Apr 25, 2014 at 1:20 PM, William Lederer <william.lederer@gmail.com> wrote:

I agree with the general sentiment that Lisp is a much safer language to build anything in. While several in this thread are pointing to bounds checking as one of the advantages that Lisp has over C and other languages, there is something else I find that is also very strong: It is easier to write programs about which a reader can reason about correctness. In Lisp, the programs tend to be closer to provable and errors are more evident. As in "obviously no deficiencies" vs "no obvious deficiencies".

But in my experience, vulnerabilities result from

• Buffer Overflows/lack of bounds checking (Heartbleed and friends)
• Configuration errors
• Logic Flaws
• Dangerous use of user input (leading to SQLi, XSS, XSRF)
• Improper use of cryptography
• Unclear protocol specification (leading to OpenSSL)

This (IMO entirely worthy and correct) summary can easily be misunderstood!  Lisp may be superior because it has bounds checking. (We've previously agreed that isn't guaranteed since it isn't in the ANS, and in any platform likely depends on optimization qualities, including the optimization qualities under which internal called routines were compiled.)  But bugs based on buffer overflow don't on normal operating systems in general involve bounds checking.  At some point on any modern OS, reading or writing to a socket stream will involve passing to the OS (generally via a thin user-mode C API layer like *nix read() and write(), or some socket analogue).  Neither Lisp nor C will provide any automatic bounds checking on such a call.  The OS treats the application's address space as a mostly-contiguous undifferentiated sea of bytes(*).  It doesn't matter that at the app level C also has this model of a sea of bytes, while in Lisp the ocean is run-time tagged into small plots.  That distinction disappears once one calls write(fd,buf,len).

The Lisp Machine in its several manifestations might be the only counterexample, since there was no C boundary over which to cross, and because type and bounds checking was performed for free in the microcode.  But Lisp machines aren't around any more largely because of the economy of scale.  The number of x86 and x64 processors on the planet must be nearly on the order of 10^9, while the number of Lisp machine processors never got out of the 10^5 range, so Intel and AMD etc. could justify huge investments making those processors 3 orders of magnitude faster in raw speed.  Lisp processors could not have kept up at bearable per-item cost.  Alas!