N3690 comment
US 3 The wording of 6.10.1 [intro.execution] paragraph 6 is
intended to describe the values of objects upon entry to and exit
from the handler — i.e., that signal handler cannot rely on
non-atomic objects being in a consistent state upon entry, nor
can it reliably set the value of non-atomic objects and expect
that they will continue to have those values after the handler
exits. However, the wording could be read as saying even during
the execution of the handler it cannot set and use non-atomic
objects. The wording should be clarified.