What does 'inline' mean?

[Manu]

On Fri, Jun 12, 2020 at 3:40 AM kinke via Digitalmars-d <
digitalmars-d at puremagic.com> wrote:

> On Monday, 8 June 2020 at 14:22:50 UTC, Manu wrote:
> > On Mon, Jun 8, 2020 at 8:30 PM kinke via Digitalmars-d <
> >> In its owning module, the function is emitted as a regular
> >> function, as a fallback for non-inlined cases (and for when
> >> people take its address etc.). Our opinions diverge wrt.
> >> whether that's a problem - to me it's clearly no big deal, as
> >> the function is a) most likely small, and b) subject to linker
> >> stripping if unreferenced.
> >
> >
> > a) most likely small, but still not nothing; the symbol table
> > is public ABI
> > material, and in some projects I've worked on, the symbol table
> > is
> > carefully curated.
> > b) linker stripped is not reliable. We are unnecessarily
> > inviting issues in
> > some cases, and there's just no reason for that.
> >
> > If we're confident that link stripping is 100% reliable when a
> > symbol is not referenced, then I have no complaint here.
> >
> > Can you show what case a hard-symbol in the owning CU solves?
> > Non-inlined
> > cases will still find it locally if it has internal linkage (or
> > whatever
> > that link flag is called).
> > I think it's the same flag that `static` (or `inline`) in C++
> > specifies
> > right?
>
> Internal linkage (C(++) static), AFAIK, means that you may end up
> with multiple identical functions in the final linked binary.
> Some linkers may be able to still fold them, such as the MS
> linker and lld with /OPT:ICF (identical COMDAT folding).
>

Actually, I might be wrong about what the link flag is called.
I'm fairly sure C++ uses the link flag that LLVM calls "choose one".
It's in the C++ spec that all inlines collapse to the same one. We should
be using the same flag.

Linkonce_odr linkage (C++ templates and `inline` functions) on
> the other hand means that you end up with either 0 or 1 function
> in the final binary, even when multiple object files define it;
> AFAIK, without having to rely on /OPT:REF or --gc-sections etc.
> At least for LLVM, linkonce_odr additionally means that the
> definition is discarded early if unused and might not make it to
> the object file at all.
>
> Weak_odr linkage (current D templates) is similar to linkonce_odr
> but not 'officially' discardable (if unreferenced) for the final
> binary (and thus always making it to the object file). This can
> be overridden by /OPT:REF and --gc-sections etc., the success of
> which also depends on symbol visibility and/or --export-dynamic
> etc.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puremagic.com/pipermail/digitalmars-d/attachments/20200612/332c4efc/attachment.htm>