strip trailing slashes in DEBUGINFOD_URLS

[Feyorsh]

A trailing slash in a url in DEBUGINFOD_URLS (the default on e.g. Fedora) causes the path to be completely ignored, resulting in a query returning nothing of value.

strip trailing slash in DEBUGINFOD_URLS
bash-5.2$ export DEBUGINFOD_URLS="https://debuginfod.elfutils.org/"
bash-5.2$ export DEBUGINFOD_VERBOSE=1
bash-5.2$ gdb
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(gdb) tar rem ...
Remote debugging using ...
Reading ... from remote target...
warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
Reading ... from remote target...
Reading symbols from target:...
warning: Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code.

This GDB supports auto-downloading debuginfo from the following URLs:
  <https://debuginfod.elfutils.org/>
Enable debuginfod for this session? (y or [n]) y
Debuginfod has been enabled.
To make this setting permanent, add 'set debuginfod enabled on' to .gdbinit.
info(debuginfod_zig): findDebuginfo 265d92b5d001e68fc815c0716b5d6bd23124fe37
info(debuginfod_zig): fetch https://debuginfod.elfutils.org//buildid/265d92b5d001e68fc815c0716b5d6bd23124fe37/debuginfo
Downloading separate debug info for system-supplied DSO at 0xffffa5ae6000
warning: `~/.cache/debuginfod_client/265d92b5d001e68fc815c0716b5d6bd23124fe37/debuginfo': can't read symbols: file format not recognized.
0x0000ffff97e00ca0 in ?? ()
(gdb)

And the contents of ~/.cache/debuginfod_client/265d92b5d001e68fc815c0716b5d6bd23124fe37/debuginfo is debuginfod (elfutils) 0.194 instead of the expected debuginfo (in this case specifically it should actually return warning(debuginfod_zig): findDebuginfo err: error.FetchStatusNotFound because the elfutils server does not have symbols for this build-id).

A simpler demonstration of the issue with curl:

bash-5.2$ curl https://debuginfod.elfutils.org//buildid/265d92b5d001e68fc815c0716b5d6bd23124fe37/debuginfo
debuginfod (elfutils) 0.194
bash-5.2$ curl https://debuginfod.elfutils.org/buildid/265d92b5d001e68fc815c0716b5d6bd23124fe37/debuginfo
not found

[patryk4815]

@Feyorsh thank you!

[patryk4815]

@Feyorsh https://debuginfod.pwndbg.re support fetching debuginfo from nix/nixpkgs, but we still didn't add fetching source code

[Feyorsh]

Oh nice, is that using nixseparatedebuginfod2?

Also unrelated, do you maybe want to add a snippet for using debuginfod-zig with Nix to the README? (I'm using it in my CTF flake, I'm sure there's probably a better way to do that though lol)

[patryk4815]

Oh nice, is that using nixseparatedebuginfod2?

didn't know it exists 🙉 We just develop version in golang that downloads debuginfo+nar from cache.nixos.org, converts .nar to .erofs, etc.. 😆 But it not yet open sourced, maybe in few months when I will have more time.

[patryk4815]

Also unrelated, do you maybe want to add a snippet for using debuginfod-zig with Nix to the README? (I'm using it in my CTF flake, I'm sure there's probably a better way to do that though lol)

Right. Probably something like should work (added to readme):

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";
    debuginfod-zig.url = "github:pwndbg/debuginfod-zig";
  };
  outputs =
    inputs@{
      self,
      nixpkgs,
      debuginfod-zig,
      ...
    }:
    let
      forAllSystems = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
      fun_pkgs =
        system:
        import nixpkgs {
          inherit system;
          overlays = [
            debuginfod-zig.overlays.default
            (final: prev: {
              gdb-with-debuginfod = (prev.gdb.override { enableDebuginfod = false; }).overrideAttrs( old: {
                 buildInputs = (old.buildInputs or []) ++ [
                    prev.libdebuginfod-zig-static
                 ];
                 configureFlags = (old.configureFlags or []) ++ [
                    "--with-debuginfod=yes"
                 ];
              });
            })
          ];
        };
    in
    {
      packages = forAllSystems (
        system:
        let
          pkgs = (fun_pkgs system);
        in
        {
          gdb-with-debuginfod = pkgs.gdb-with-debuginfod;
        }
      );
    };
}