The previous API of returning two `unsigned`s was ambiguous when accessing the second member of a union that is the first member of a struct, where both output were set to zero.
It now returns one `unsigned` and an output `bool` to determine if it should be used as either a field or byte offset.
Make -linkonce-templates *not* tamper with the general template
emission algorithm anymore (so on top of default non-allinst or
-allinst modes), and keep those tweaks as experimental
-linkonce-templates-aggressive.
Compiling the druntime/Phobos unittests is only marginally slowed
down compared to the more aggressive variant (~1.5% for debug,
~2.5% for release). It does show some rough 10% increase in required
memory, but that's in line with non-linkonce-templates.
The more aggressive variant has the advantage of skipping
needsCodegen() and potentially codegen'ing less symbols. The problem
is that if an instantiated symbol isn't explicitly referenced, for
instance a CRT ctor, it might not be codegen'd at all.
The linkage now (2.098) also affects the size of empty structs - e.g.,
1 for extern(C++), 0 for Posix extern(C), 4 for MSVC extern(C).
This also affects beauties like `extern(C) struct S { double[0] a; }`,
as tested by dmd-testsuite's runnable/ldc_cabi1.d, which is hereby
fixed for Posix - don't try to GEP into an empty LL struct.
A clean way of directly accessing struct and class init symbols. It
yields a `const(void[])` slice; the length reflecting the struct/class
instance size, and the pointer either pointing to the init symbol or
being null for zero-initialized structs.
Paves the way for resolving #3773 in druntime as well as accessing class
init symbols without `TypeInfo_Class.initializer()` indirection, and so
with -betterC as well.
* Newly require `-link-defaultlib-shared` for implicit dllimport.
E.g., this enables to compile druntime DLL with `-fvisibility=public`
for pure exports and no (local) imports (such as builtin TypeInfos).
* `-link-defaultlib-shared` alone now only implicitly imports symbols
from druntime/Phobos.
This simplifies building complex DLLs linked against a bunch of
static libs (dub only supports static lib dependencies!); the static
libs don't need to be compiled with `-fvisibility=public` anymore
(if the DLL itself isn't either), `-link-defaultlib-shared` is
sufficient.
This is mainly useful for existing DLLs with explicit exports, to make
them link against *shared* druntime/Phobos and so end up with a single
druntime/Phobos for the whole process.
Init symbols, TypeInfos (classes only) & vtables - unless defined in a
root module. For explicitly exported aggregates, or, with
`-fvisibility=public`, all aggregates.
