debug symbols (`enableDebugging` and `separateDebugInfo`) broken on darwin

[patryk4815]

Describe the bug

environment.enableDebugInfo Or separateDebugInfo Or enableDebugging Not working as excepted. It should produce "package" with debug symbols.

The macOS linker doesn't link debug information into the final binary the way linkers usually do on other Unixen. Rather it leaves the debug information in the .o files and writes a "debug map" into the binary that tells the debugger how to find and link up the debug info read from the .o files. The debug map is stripped when you strip your binary.

Steps To Reproduce

Steps to reproduce the behavior:

$ nix-build -E 'with import <nixpkgs> {}; hello.overrideAttrs (old: { separateDebugInfo = true; })' --no-out-link --keep-failed;

post-installation fixup
gzipping man pages under /nix/store/jz7f3bwrqc5m02a05f5xkd1sixc5w1a0-hello-2.12.1/share/man/
strip is /nix/store/fb4rdxr69sy1vsi98z3njxjzdq3rj3ah-clang-wrapper-11.1.0/bin/strip
stripping (with command strip and flags -S) in  /nix/store/jz7f3bwrqc5m02a05f5xkd1sixc5w1a0-hello-2.12.1/bin
patching script interpreter paths in /nix/store/jz7f3bwrqc5m02a05f5xkd1sixc5w1a0-hello-2.12.1
/nix/store/jz7f3bwrqc5m02a05f5xkd1sixc5w1a0-hello-2.12.1

$ nm -pa /nix/store/jz7f3bwrqc5m02a05f5xkd1sixc5w1a0-hello-2.12.1/bin/hello | grep OSO
//empty

^ debug dir is not created. And debug map is missing.

$ nix-build -E 'with import <nixpkgs> {}; enableDebugging hello'
make[2]: Leaving directory '/private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1'
make[1]: Leaving directory '/private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1'
post-installation fixup
gzipping man pages under /nix/store/dfl5gqgkksg4n8xlxckn3lra4ag8bjg0-hello-2.12.1/share/man/
patching script interpreter paths in /nix/store/dfl5gqgkksg4n8xlxckn3lra4ag8bjg0-hello-2.12.1
/nix/store/dfl5gqgkksg4n8xlxckn3lra4ag8bjg0-hello-2.12.1

$ nm -pa /nix/store/dfl5gqgkksg4n8xlxckn3lra4ag8bjg0-hello-2.12.1/bin/hello | grep OSO                                                                                                          
0000000063a9521c - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/src/hello.o
0000000063a9521c - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(c-strcasecmp.o)
0000000063a9521d - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(close-stream.o)
0000000063a9521d - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(closeout.o)
0000000063a9521d - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(exitfail.o)
0000000063a9521d - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(localcharset.o)
0000000063a9521d - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(progname.o)
0000000063a9521e - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(propername.o)
0000000063a9521e - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(quotearg.o)
0000000063a9521e - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(version-etc.o)
0000000063a9521e - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(version-etc-fsf.o)
0000000063a9521f - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(xmalloc.o)
0000000063a9521f - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(xalloc-die.o)
0000000063a9521f - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(error.o)
0000000063a9521f - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(fpending.o)
0000000063a9521f - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(getopt.o)
0000000063a9521f - 00 0001   OSO /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/./lib/libhello.a(getopt1.o)

^ debug map was created, but debug symbols missing, because they are in .o files (/private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/ was removed after build)

Expected behavior

a) Lets disable support for darwin in enableDebugging / separateDebugInfo / enableDebugInfo (and throw exception) b) enableDebugging:

• lets add extra steps in postFixup phase, eg. for packaging .o files 🤔
• and we need patch binary debug map path from /private/tmp/nix-build-hello-2.12.1.drv-0/hello-2.12.1/ to /nix/store/XXX 🤔

c) separateDebugInfo - don't know if it will work

Notify maintainers

@NixOS/darwin-maintainers

[veprbl]

See also #203380

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/single-cmakebuildtype-shared-between-derivation-and-dependency/35184/3

[n8henrie]

For rust, one can specify RUSTFLAGS='-C split-debuginfo=packed' and the debug information is then put into a .dSYM directory that can easily be included in $out and seems to work.

https://github.com/NixOS/nixpkgs/issues/262131