Splitting Debuginfo

[Gankra]

Another future killer app: properly setting the flags and running the tools to produce proper symbol/debuginfo files (similar to source maps, but for native code).

This comment covers a lot of useful details on the state of this stuff in rust.

Some quick notes:

Each platform has different formats for this:

• windows pdb
• apple dsym
• linux dwp
• breakpad (platform-agnostic) sym

Different platforms have different symbol servers:

• windows symbol server (can fetch exe/dll/pdb)
  • breakpad generalizes this for .sym, see mozilla's tecken
• linux debuginfod
• apple: just ask xcode lolsob
• android: suck eggs

To generate symbol files for rust you want to:

• build a release binary
  • with opt-level=3 or w/e release is
  • with codegen-units=1
  • with LTO..?
• with debug info cranked to max
  • build with debug=2
  • enable split-debuginfo which is horribly platform specific
• if targetting breakpad: run dump_syms to get a .sym
• strip the binary?

Then the user will want to:

• grab the final debuginfo/symbol file
• get the unique build ids that map the debuginfo to the binary (platform-specific, hopefully embedded in the file, but we should still get them out?)
• upload it to a symbol server?
• package it?

[Gankra]

We generate the pdb and upload it to the release, however we don't:

• handle dsym (it's a directory so as it turns out we might need to zip it up)
• handle dwp (upstream cargo issue, dwp's aren't quite ready for primetime)
• grab ids (haven't bothered yet)

[Gankra]

dwp is blocked on rust-lang/cargo#11572

dsyms would be nice to do before shipping...

[Gankra]

The cargo issue was fixed (obvs needs to ride the trains) but rust-lang/rust#105991 is also an argument against using it.

[mstange]

Some additional info for macOS symbol servers:
Yes, there is no symbol server scheme on macOS, but there are bunch of alternatives, including the ability to plug in a custom "find my dSYM" script, and also we can just decide on our own scheme.

The alternatives are described here: https://lldb.llvm.org/use/symbols.html

As for a macOS symbol server URL scheme, for the Mozilla symbol server I'm planning to use the following scheme: https://symbols.mozilla.org/uuid/D13BD7EC88D830C49C6BC4B34F2D9156/debuginfo.dSYM.tar.bz2

And then we can supply an off-the-shelf script for use with DBGShellCommands which supports this scheme, and also teach wholesym about it.