On Monday, 5 February 2018 at 21:27:57 UTC, H. S. Teoh wrote:
One of my D projects for the past while has been taking
unusually long times to compile. This morning, I finally
decided to sit down and figure out exactly why. What I found
was rather disturbing:
------
import std.regex;
void main() {
auto re = regex(``);
}
------
Compile command: time dmd -c test.d
Output:
------
real 0m3.113s
user 0m2.884s
sys 0m0.226s
------
Comment out the call to `regex()`, and I get:
------
real 0m0.285s
user 0m0.262s
sys 0m0.023s
------
Clearly, something is wrong if the mere act of compiling a
regex causes a 4-line program to take *3 seconds* to compile,
There is a fuckton of templates involved, plus a couple of tries
are built at CTFE.
The regression is curious though, maybe something gets recomputed
at CTFE over and over again.
where normally dmd takes less than a second.
Honestly I’m tired to hell of working with our compiler and its
compile time features. When it doesn’t pee itself due to OOM I’m
almost happy.
In retrospect I should have just provided a C interface and
compiled the whole thing separately. And CTFE could easily be
replaced by a small custom JIT compiler, it would also work at
run-time(!).
Especially considering that it’s been 6 years but it’s still is
not practical to use ctRegex.
The latter department as also suffered a regression; see for
example: https://github.com/dlang/phobos/pull/5981.)
Yup, Martin seems on top of it, thankfully.
T
