Hi,
I am trying to split debug symbols out of final binary, to reduce
its size. But I would like to preserve at least line numbers in
the stacktraces from `Exception`s.
Linux, amd64. gdc 12.2.0 on Debian testing.
Binary is compiled using `-O3 -g -g3` (and possibly -gz).
I then use `objcopy` to split debug info from final ELF binary
file into .exe and .debug files.
I use `objcopy --only-keep-debug --compress-debug-sections=zlib
binary binary.debug` to produce .debug file.
Then I use normally `objcopy --strip-debug binary binary.exe`
(possibly with --compress-debug-sections=zlib) to produce binary.
This makes it possibly to use in gdb without issues (using `gdb
-s binary.debug -e binary` for example, or by utilizing
`--add-gnu-debuglink=` option in `objcopy`).
But this causes stacktraces to miss line numbers (and columns).
(function names are still there, as these are derived from symbol
tables instead).
I tried selectively removing DWARF debug sections, but it looks
that at least these are required:
`.debug_info`
`.debug_aranges`
`.debug_abbrev`
`.debug_line`
`.debug_str`
`.debug_line_str`
`.debug_rnglists`
So, I can only remove these:
`objcopy -R .debug_loc -R .debug_macro -R .debug_ranges -R
.debug_loclists`
(`.debug_loc` and `.debug_ranges` are not even generated by gcc,
so it does not matter probably).
The issue is, this saves me very little space. `.debug_macro` and
`.debug_loclists` are rather small.
The bulk of information is in `.debug_info`. But I believe it
contains way more information than is really needed to just
produce line numbers.
I did inspect final binaries , and it is using DWARF version 5.
I also tried `-gas-loc-support` , but no change.
Using `-g1` makes stack traces work nicely, by making
`.debug_info` smaller, but then debugging in `gdb` is very
limited. One option would be to compile application twice, once
with `-g1` and once with `-g3`. But I really do not think this is
supported, or reliable, even if I enable deterministic builds.
In one article (
https://support.backtrace.io/hc/en-us/articles/360040105792-DWARF#RemovingDebugInformation ) I read that for C/C++ in GCC, it is enough to preserve only `.debug_frame` and `.debug_line` to get function, source filenames and line numbers. But that is not true for gdc and its stacktrace handler.
I did read about this gdb extension, which is interesting,
https://sourceware.org/gdb/onlinedocs/gdb/MiniDebugInfo.html ,
but I did not try, and it is probably only supported in gdb (i.e.
addr2libe, Phobos, libunwind do not support it).
Any ideas?
