Re: set sysroot and debug-file-directory don't work together?

>>>>> "Mike" == Mike Tsai via Gdb <[email protected]> writes:

Mike> I have a dummy question regarding using "set sysroot LOCAL_DIR" and
Mike> "set debug-file-directory SOME_OTHER_DIR" together to find symbols for
Mike> a debug session. I was under the impression, gdb is able to fallback
Mike> to debug-file-directory and do build-id style lookup if symbols cannot
Mike> be found in "sysroot", but it does not seem to be doing that so I am
Mike> curious if it's I am doing something wrong or this is not "supported".

I didn't know the answer either, so I looked through the source a bit.

In the end it's just a pain to try to figure out what this code is
doing.  Far easier, probably, is for you to:

    set debug separate-debug-file 1

... and then try.  I think that will show exactly the paths gdb is
trying to use.

I tried it with "file /bin/ls":

    (gdb) file /bin/ls
    Reading symbols from /bin/ls...

    Looking for separate debug info (build-id) for /usr/bin/ls
      Trying /usr/lib/debug/.build-id/a1/46002a40b622e4d8420c5b96513f0784c8eb7b.debug... no, unable to compute real path
      Trying target:/usr/lib/debug/.build-id/a1/46002a40b622e4d8420c5b96513f0784c8eb7b.debug... no, unable to open.

    Looking for separate debug info (debug link) for /usr/bin/ls
      Trying /usr/bin/ls-9.1-12.fc38.x86_64.debug... no, unable to open.
      Trying /usr/bin/.debug/ls-9.1-12.fc38.x86_64.debug... no, unable to open.
      Trying /usr/lib/debug//usr/bin/ls-9.1-12.fc38.x86_64.debug... no, unable to open.
    Reading symbols from .gnu_debugdata for /usr/bin/ls...
    (No debugging symbols found in .gnu_debugdata for /usr/bin/ls)

... IMO pretty readable.

If I "set sysroot /tmp/nonesuch" first, then only that "target:" line
changes.

This order seems sort of backward to me somehow, like if I had a
complete sysroot setup (including all separate debug files), then "set
sysroot" should be sufficient and it should never check outside.  I
suppose with .build-id the idea is that the hashes are global and so it
doesn't matter exactly where gdb finds the match.

Tom