## staticExec is wrong approach staticExec is a bad approach to solve this kind
of problem more generally (whether it's for regex, rand, getTime, and hosts of
other things that require importc procs).
* large performance overhead (especially if what you need is something that
measures time, which needs low overhead to avoid affecting what you're
measuring)
* higher complexity (need a separate binary / shell command to run,
serializing input, deserializing output, and making sure the binary doesn't
produce spurious unrelated data to stdout etc)
In the end you end up duplicating existing functionality for no gain.
## overloading (via vmops) getTime as staticTime (more genrally foo =>
staticFoo) is usually bad Introducing a static overload in vmops is often a
good thing, but what's bad is renaming it differently when it is a simple CT
wrapper that does the exact same thing at CT, eg foo=>staticFoo.
A common argument in favor of renaming is to prevent against user errors when
they write const a = foo(), and intended to write let a = foo(), however that's
just the desired behavior here, const vs let have different, well understood
semantics.
Renaming is bad because code that works at RT should work at CT as much as
possible, otherwise useful functionality is lost when needed at CT and we have
to re-invent the wheel or use silly workarounds like when nimvm to undo the
distinction eg:
template runBench(fun)
when nimvm: let t = staticTime()
else: let t = getTime()
fun()
...
Run
All that's needed, more generally, is a flag \--enablevmops:Foo if we want to
disable by default some features at CT, but we should not rename them
**unless** their CT behavior is modified (like staticRead etc)
## CT FFI approach (more general, has some caveats)
* with CT FFI (-d:nimHasLibFFI) you can already do what you want as follows:
# import std/timers # pending https://github.com/nim-lang/Nim/pull/13617
include system/timers
proc main(): auto =
let t1 = getTicks()
# run some code
let t2 = getTicks()
# echo t2.int64 - t1.int64 # works but we should used timers.`-`
# echo t2-t1 # Error: cannot evaluate at compile time: timeBaseInfo
result = (t1, t2)
const (t1, t2) = main()
echo ("nanos: ", t2 - t1)
Run
this works today; it could be improved so that t2-t1 also works in VM so we
wouldn't need to return the tuple, but that should be fixable as future
enhancement to CT FFI
## vmops cpuTime you can also use cpuTime at CT via \--benchmarkVM However, it
should error instead of giving an arbitrary result as it does right now when
\--benchmarkVM is not passed:
if optBenchmarkVM in c.config.globalOptions:
wrap0(cpuTime, timesop)
else:
proc cpuTime(): float = 5.391245e-44 # Randomly chosen
wrap0(cpuTime, timesop)
Run
