[Issue 16291] phobosinit fails to register encodings on individual tests

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=16291

--- Comment #4 from Ketmar Dark <ketmar at ketmar.no-ip.org> ---
as nothing directly referring to module ctors, linker just doesn't know that it
should not optimize 'em away. maybe we can fix that by emiting some flag for .o
files, but i don't really know -- i never even read about dwarf object file
format, so i'm not sure if such flag exists.

that is, linker really does it's work here: if nothing directly using the
symbol from object file, that object file is not linked to the final binary.
tbh, i don't know how can we solve this: if we will mark all module ctors as
"include always" (if it's possible), we will have alot of unnecessary (and
probably unused) code linked to the final binary. it doesn't hurt much, but
still...

for now, easy fix is to move that thing back to "std.encoding", as it seems to
not conflict with anything now. and probably create a new issue that documents
this behavior.

maybe we can introduce some UDA to mark modules that should not be optimized
away by smartlinking, or something like that, 'cause i guess that similar
issues are very possible in the future, as phobos becomes more and more
complex, with complex interdependencies.

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