The index item 'program execution' is marked from page 10 ([intro.abstract], 4.1.2), to page 80 (before [intro.multithread], 6.9.2).
I think this was caused by adding [intro.multithread] section, and latter restructured by moving both [intro.execution] and [intro.multithread] into [basic] as a whole, carrying the index ending mark within them.

I think the range of 'program execution' should contain the contents of both [intro.abstract] and [basic.exec] sections.