On Friday, 25 March 2016 at 19:04:46 UTC, Anon wrote:
Two changes to the mangling:
1) `LName`s of length 0 (which currently cannot exist) mean to
repeat the previous `LName` of the current symbol.
2) N `Number` is added as a valid `Type`, meaning "Type Back
Reference". Basically, all instances of a
struct/class/interface/enum type in a symbol's mangling get
counted (starting from zero), and subsequent instances of that
type can be referred to by N0, N1, N2, etc.
I have implemented the second part (simplest I thought) to see
what it would bring (in LDC). 'Q' seems unused, so I used that
instead of 'N' ;)
I'm not 100% certain of the implementation, as it relies on DMD
using the same pointer values for recurring types but it seemed
to work with complicated code.
The core.demangle demangler was relatively easy to upgrade for
repeated types.
Unfortunately, and perhaps expectedly, it did not give a large
size reduction / speed boost. Not very statistically sound
results though ;)
The change is relatively easy, I think, so perhaps it is still
worthwhile pursuing.
An implementation issue that changes in mangling have to deal
with:
One surprising thing was that std.traits uses the mangled name in
`ParameterStorageClassTuple`. So std.traits contains its own mini
mangling parser, and also calls .mangleof on Types, to skip to
the next function argument in the mangled function string. The
"type back reference" scheme means that Type.mangleof may not
correspond to how the Type embedded in the mangling of a
function, and so I had to upgrade std.traits with its own parser
(I copied core.demangle.Demangle, and removed all output
complications).
For changes in mangling, it'd be good if
std.traits.ParameterStorageClassTuple could be rewritten to not
use the mangled function name + string processing.
