Support for NIX_DEBUG_INFO_DIRS? #24
Description
nixpkgs patches all the debuggers and similar things on the system to use NIX_DEBUG_INFO_DIRS to provide debuginfo to them. I am not sure the "normal" way to do this, but nix likely needs to do it this way to separate the debug info completely from the executables.
This environment variable points to a colon separated list of directories that look like this:
$ ls -la /nix/store/rg9fcbxbvy11s7k2mcm0lawy3mr6hnqj-lix-2.93.0-dev-pre20250224-945e674-debug/lib/debug
total 7
dr-xr-xr-x 3 root root 10 Dec 31 1969 .
dr-xr-xr-x 3 root root 3 Dec 31 1969 ..
dr-xr-xr-x 9 root root 9 Dec 31 1969 .build-id
lrwxrwxrwx 1 root root 57 Dec 31 1969 liblixcmd.so -> .build-id/e8/e34f38dcd81be6179a91cd00457afec379d2a2.debug
lrwxrwxrwx 1 root root 57 Dec 31 1969 liblixexpr.so -> .build-id/3e/e59d82e59d5be9c529f748dee3b66aeba6732f.debug
lrwxrwxrwx 1 root root 57 Dec 31 1969 liblixfetchers.so -> .build-id/f5/0cb975e366879b0c4ace3a16bb922da47f7b91.debug
lrwxrwxrwx 1 root root 57 Dec 31 1969 liblixmain.so -> .build-id/bc/ff2e67f9db67b4331160272e5755c51de332e4.debug
lrwxrwxrwx 1 root root 57 Dec 31 1969 liblixstore.so -> .build-id/2c/2e1f6133b8e7cb9330cfd8a271b51ac2f2fc30.debug
lrwxrwxrwx 1 root root 57 Dec 31 1969 liblixutil.so -> .build-id/7a/3fe512e965b6e0190ecf8911159d8f32feb15b.debug
lrwxrwxrwx 1 root root 57 Dec 31 1969 nix -> .build-id/ae/f9fb63a1b210c0c21d981e75dcda406cc943d3.debug
$ file $(realpath /nix/store/rg9fcbxbvy11s7k2mcm0lawy3mr6hnqj-lix-2.93.0-dev-pre20250224-945e674-debug/lib/debug/nix)
/nix/store/rg9fcbxbvy11s7k2mcm0lawy3mr6hnqj-lix-2.93.0-dev-pre20250224-945e674-debug/lib/debug/.build-id/ae/f9fb63a1b210c0c21d981e75dcda406cc943d3.debug: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter *empty*, BuildID[sha1]=aef9fb63a1b210c0c21d981e75dcda406cc943d3, for GNU/Linux 3.10.0, with debug_info, not stripped
I would like to be able to upload traces from executions of such programs, ideally by using the familiar environment variable as I would do for rr replay on Nix systems.
This is the gdb patch used to implement these:
https://github.com/nixos/nixpkgs/blob/e6491be4e39a7dcd1337ba50cccc00a59c8f44aa/pkgs/development/tools/misc/gdb/debug-info-from-env.patch#L1-L17
I think I can do the sources by --copy-sources? I am not sure what --build-dir does and whether it is the NIX_DEBUG_INFO_DIRS behaviour; at the very least it seems to be in the singular, which seems like it might be a problem.