From http://en.cppreference.com/w/cpp/language/constexpr:
A constexpr specifier used in an object declaration implies const.
However, We can not change from
static constexpr const char* TIME_FORMAT = "%a %b %d %I:%M:%S %Z %Y";
to
static constexpr char* TIME_FORMAT = "%a %b %d %I:%M:%S %Z %Y";
The compiler complains:
In file included from json/formatter.cc:22:0:
json/formatter.hh:132:42: error: deprecated conversion from string
constant to ‘char*’ [-Werror=write-strings]
static constexpr char* TIME_FORMAT = "%a %b %d %I:%M:%S %Z %Y";
Since, unlike const, constexpr does not modify a type. It just applies
to an object (or function), and incidentally implies const to the
top-level type.
swapcontext() is expensive as it invokes system calls. Replace it with
setjmp()/longjmp(). We still use setcontext() initially, since that's
the most reasonable portable method of setting up a stack.
Context switch time (measured by thread_context_switch) is reduced to
120ns (from 450ns), with inefficiencies in the test itself and in future<>
dominating.
Add a thread class that can be used to launch a blockable thread of
execution. Within a thread, future<>::get() can be called on an
unavailable future, in which case it blocks until the future is made ready.
