While working on some new bindings, I've discovered that if opAssign in a struct template "BindingTempl(T)" has the return type "BindingTempl!T then it adds about 4 seconds to the compile time per instantiation of BindingTempl. The added compile time is much lower if a function other than opAssign returns BindingTempl!T. Is opAssign a particularly bad operator to overload in templates or something?

On 7/9/23 7:54 AM, IchorDev wrote:

This is probably a bug somewhere, 4 seconds is too much. A reduced test case would be helpful.

But I wanted to note, inside a struct template, the template name (by itself) is equivalent to the current instantiation. So just returning BindingTempl would be equivalent, and might not trigger this problem.

See if that helps.

-Steve

On Sunday, 9 July 2023 at 14:49:39 UTC, Steven Schveighoffer wrote:

Thank you for letting me know about being able to use BindingTempl, I had no idea! Unfortunately it doesn't mitigate the compile times, though.
I forgot to mention, it only happens when specifying -O with DMD. LDC and GDC compile the same thing almost instantly.
Boiling it down to a simple test is tough. If you remove a lot of components the struct template depends on then the compile time is too fast for anything to be noticeable. I think the issue is some kind of snowball-effect.

If anyone wants to try to reproduce this issue:

1. Download this exact commit of the WIP BindBC-ImGui repo. (the newer commits won't compile)
2. Edit dub.selections.json to change "bindbc-common"'s version to "0.0.6".
3. Run:

dmd -extern-std=c++11 -lib -O -version=BindImGui_Static -Isource/ -I~/.dub/packages/bindbc-common/0.0.6/bindbc-common/source/ source/bindbc/imgui/config.d source/bindbc/imgui/package.d source/imgui/impl.d source/imgui/package.d -v

4. Now, remove -O from the dmd command. Blink and you'll miss it compiling!