When using separate compilation, DMD emits and calls many duplicate static dtors. In one larger code base I found the counter at 76 while debugging an issue. Here is a reduced test case that creates only one duplicate:
----------8<----------
module main;
import a, b;
void main()
{
A a;
B b;
}
---------->8----------
----------8<----------
module a;
import res;
struct A { Block!() field; }
---------->8----------
----------8<----------
module b;
import std.typecons, res;
struct B { Block!() field; }
---------->8----------
----------8<----------
module res;
struct Block()
{
import core.stdc.stdio;
shared static ~this() { debug printf ("struct Block shared static dtor %s\n", __FUNCTION__.ptr); }
static ~this() { debug printf ("struct Block static dtor %s\n", __FUNCTION__.ptr); }
}
---------->8----------
This prints on DMD 2.066.1 and 2.065.0:
struct Block static dtor res.Block!().Block._staticDtor6
struct Block static dtor res.Block!().Block._staticDtor4
struct Block shared static dtor res.Block!().Block._sharedStaticDtor5
struct Block shared static dtor res.Block!().Block._sharedStaticDtor3
On DMD 2.064.2 the output was:
struct Block static dtor res.Block!().Block._staticDtor11
struct Block static dtor res.Block!().Block._staticDtor4
struct Block shared static dtor res.Block!().Block._sharedStaticDtor10
struct Block shared static dtor res.Block!().Block._sharedStaticDtor3
Tagged as wrong code, like when a common dtor would be called twice by the runtime.
P.S.: I also wonder what the static dtors 1 and 2 are created for. I often get runtime errors about circular dependencies of modules with static constructors, but cannot see any in the respective modules.
Comment #1 by Marco.Leise — 2014-11-10T11:04:38Z
On a side note I also found the debug build executable size to increase from 5.4 to 16 MiB when using separate compilation. That is 3x the size and doesn't seem like a reasonable difference for a linked executable. This must be duplicated stuff that could not be merged.
Comment #2 by robert.schadek — 2024-12-13T18:33:40Z