https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59075
--- Comment #11 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #10)
> Tom, do you know why the types might be shown differently on OS X and
> GNU/Linux? (see comments 7 and 8).
>
> Is that because of something different in the DWARF? Is that expected for OS
> X, or is it a GCC bug?
Can we check that this is still current on trunk after the fix for 70694 was
applied - since that alters visibility of some symbols (maybe a long shot).
It's not expected that Darwin will do anything differently modulo (1) it
doesn't use .cfi_xxx at present, (2) it's generally limited to DWARF2 [a
historical issue with older versions of dsymutil, see below], although I hope
to lift that restriction soon, since we now have a DWARF4-capable dsymutil
However ...... the status quo is:
Darwin has the following strategy for debug.
1. the static linker ignores DWARF but writes a table of object file locations
into the executable.
2a. the executable + the object files can be consumed by a debug client (e.g.
GDB)
- the table in the exe tells the client where to find the objects and it
can read/link the DWARF from them directly. This often makes sense for a
developer who is doing a lot of compile/edit/debug loops. GDB understands this
approach (last i tried),
2b. if one doesn't want to keep the objects around; the executable + the
objects can be consumed by "dsymutil" this is Darwin's debug linker, which
produces a monolithic debug object (which can be consumed alongside the actual
executable to provide the debug data). For whatever reason, the design wraps
this linked debug object in a macOS package structure thus:
<exename>.dSYM/
Contents/
Resources/
DWARF/
exename
This applies to any DSO, so shlibs are the same (for libstdc++ the 'exename'
would be libstdc++.dlib).
- I'm not 100% sure whether upstream GDB still (or ever did) understands the
packaged version, Apple's GDB did - but that's long out of date.
==
As for reading Mach-O DWARF, binutils works for x86_64-apple-darwin last I
tried (you have to point it at the actual linked DWARF tho, I don't think any
of the tools understand the .dSYM package layout).
Alternately, the llvm binutils look-alikes are getting more compatible and
consume Mach-O.
Caveat, I've, but not built/tested binutils / GDB for at least 6 months on
Darwin, so my comments might be out of date.
