This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 110b. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
[Voted into WP at October, 2009 meeting.]
The execution requirements on a conforming implementation are described twice in the Standard, once in 6.9.1 [intro.execution] paragraphs 5-6 and again in paragraph 11. These descriptions differ in at least a couple of important ways:
The most significant discrepancy has to do with the way output is described. In paragraph 11, the least requirements are described in terms of data written at program termination, clearly allowing arbitrary buffering, whereas in paragraph 6, the observable behavior is described in terms of calls to I/O functions. For example, there are compilers which transform a call to printf with a single argument into a call to fputs. That's valid under paragraph 11, but not under paragraph 6.
Also, in paragraph 6, volatile accesses and I/O operations are included in a single sequence, suggesting that they are equally constrained by sequencing requirements, whereas in paragraph 11, they are clearly not.
There are also editorial discrepancies that should be cleaned up.
Proposed resolution (September, 2009):
The resolution of issue 785 also resolves this issue.