In `ld -r` mode, the linker will emit `N_GSYM` for any defined
external symbols as well as private externals. In the former case,
the thing is easy since `N_EXT` bit will be set in the nlist's type.
In the latter however we will encounter a local symbol with `N_PEXT`
bit set (non-extern, but was private external) which we also need
to include when resolving symbol stabs.
The major change in the logic for parsing symbol stabs per input
object file is that we no longer try to force-resolve a `N_GSYM`
as a global symbol. This was a mistake since every symbol stab
always describes a symbol defined within the parsed input object file.
We then work out if we should forward `N_GSYM` in the output symtab
after we have resolved all symbols, but never before - intel we lack
when initially parsing symbol stabs. Therefore, we simply record
which symbol has a debug symbol stab, and work out its precise type
when emitting output symtab after symbol resolution has been done.
This is incredibly confusing and I really need to simplify it.
Elf also possesses this shortcoming so once I get Coff up to speed
it should hopefully become clear on how to refactor this.
Structs were previously using `SegmentedList` to be given indexes, but
were not actually backed by the InternPool arrays.
After this, the only remaining uses of `SegmentedList` in the compiler
are `Module.Decl` and `Module.Namespace`. Once those last two are
migrated to become backed by InternPool arrays as well, we can introduce
state serialization via writing these arrays to disk all at once.
Unfortunately there are a lot of source code locations that touch the
struct type API, so this commit is still work-in-progress. Once I get it
compiling and passing the test suite, I can provide some interesting
data points such as how it affected the InternPool memory size and
performance comparison against master branch.
I also couldn't resist migrating over a bunch of alignment API over to
use the log2 Alignment type rather than a mismash of u32 and u64 byte
units with 0 meaning something implicitly different and special at every
location. Turns out you can do all the math you need directly on the
log2 representation of alignments.
