Fixes#31797
I finally had time to work on this.
I've implemented it so that, when an adjacent dSYM exist and its uuid match that of the current binary, we load its DWARF and use that for all getDwarfForAddress requests.
All of this is done eagerly at `MachOFile.load` for simplicity rather than later and lazier. Happy to change that to whatever you think is best.
This implementation is quite minimal and makes dSYM support "best-effort" as in, it treats dSYM parsing error as non-fatal and fallbacks using the current stabs/ofiles mechanism.
You can test it that way on macOS:
```
zig build-exe panic.zig
dsymutil panic -o panic.dSYM
strip -S panic
./panic
```
with panic.zig:
```
pub fn main() void {
@panic("panic");
}
```
Before:
```
thread 57569166 panic: panic
???:?:?: 0x103071c2b in _panic.main (/private/tmp/panic)
???:?:?: 0x103071bb3 in _main (/private/tmp/panic)
???:?:?: 0x180d5ab97 in start (/usr/lib/dyld)
fish: Job 1, './panic' terminated by signal SIGABRT (Abort)
```
After:
```
thread 57569653 panic: panic
/private/tmp/panic.zig:2:5: 0x1029d771b in main (panic)
@panic("panic");
^
/Users/cerisier/code/codeberg.org/ziglang/zig/lib/std/start.zig:698:59: 0x1029d76a3 in callMain (panic)
if (fn_info.params.len == 0) return wrapMain(root.main());
^
???:?:?: 0x180d5ab97 in start (/usr/lib/dyld)
fish: Job 1, './panic' terminated by signal SIGABRT (Abort)
```
Reviewed-on: https://codeberg.org/ziglang/zig/pulls/35582
Reviewed-by: mlugg <mlugg@noreply.codeberg.org>
Some dwarf section names like __debug_str_offsets don't fit in a Mach-O
sectname buffer, so their actual name in Mach-O binaries is truncated.
When searching for sections to load an object file's debug info, we now
compare the section name with the truncated name. Before, the full name
was checked, so we would unconditionally skip __debug_str_offsets dwarf
sections.
Apple's ld emit N_BNSYM and N_ENSYM to mark the start and end of
functions, while ld64.lld doesn't.
This resulted in MachOFile.load bailing out on unsupported STABS
layout when the linker used is ld64.lld.
This commit supports both layouts.
Like ELF, we now have `std.debug.MachOFile` for the host-independent
parts, and `std.debug.SelfInfo.MachO` for logic requiring the file to
correspond to the running program.
Corentin Kerisit