I found this on bugzilla.
http://d.puremagic.com/issues/show_bug.cgi?id=2278
So it's not really a bug. Yet there is no simple workaround. And gap
between int and double looks strange when stack frame itself is unaligned.
btw, is there no explicit alignment for variables in D at all?
align(8) double d; compiles if d is global, but it does nothing.
import core.stdc.stdio: printf;
align(8) int a;
align(8) double d;
void main() {
printf("%u %u\n", (cast(size_t)&a) % 8, (cast(size_t)&d) % 8);
}
This _always_ prints "4 4" for me. It seems that globals are not affected
by environment, but not aligned anyway.
Honestly, I'm lost :) It all works not as expected but then again I can't
find any evidences that my expectations are valid.
On Sat, 18 Dec 2010 01:57:44 +0300, bearophile <[email protected]>
wrote:
Nick Voronin:
Looks like alignment of local variables is somewhat broken.
This is a very nice bug. If not already present then please add it to
Bugzilla. If you don't want to add it, then I will add it myself. I have
modified your code like this:
import core.stdc.stdio: printf;
void main() {
int a;
double d;
printf("%u %u\n", (cast(size_t)&a) % 8, (cast(size_t)&d) % 8);
}
And this shows the performance difference:
import core.stdc.stdio: printf;
import std.date: getUTCtime, ticksPerSecond;
void main() {
double d = 0.0;
auto t0 = getUTCtime();
for (size_t i = 0; i < 100_000_000; i++)
d += 1;
auto t1 = getUTCtime();
printf("%lf\n", d);
printf("%u\n", (cast(size_t)&d) % 8);
printf("%lf\n", (cast(double)t1 - cast(double)t0) / ticksPerSecond);
}
Bye,
bearophile
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