Customers, customers, customers

The recent posts on extremely minor undefined behaviors in zlib neatly tie in with a discussion on John Regehr's blog about the future-proofitude of C and C++.

Another insightful post in this regard is this one by Derek Jones. Derek claims that the situation is different for proprietary compilers with paying customers. The argument rings true to me. The only proprietary compiler I know that competes with GCC or Clang in terms of aggressive optimization (at the cost of breakage of existing code) is the Intel C++ compiler. But that is not a counter-example: I did not pay for icc nor do I know anyone who pays for it in order to use it in production.