[Bug gdb/31088] New: gdb requires build directories to exist

[Bug gdb/31088] New: gdb requires build directories to exist

[giecrilj at stegny dot 2a.pl]

https://sourceware.org/bugzilla/show_bug.cgi?id=31088

            Bug ID: 31088
           Summary: gdb requires build directories to exist
           Product: gdb
           Version: 12.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: giecrilj at stegny dot 2a.pl
  Target Milestone: ---

Summary:

gdb cannot move up a directory that does not exist in the source tree when
looking for a source file.

Steps to reproduce on Ubuntu 22.04:

1. {
  DEBUGINFOD_URLS='https://debuginfod.ubuntu.com' &&
  export DEBUGINFOD_URLS; }

2. set debuginfod enabled on

3. attach to a running yelp

3.1. debuginfod will download debuginfo and refuse to download source files

4. {
  cd
"${HOME}/.cache/debuginfod_client/a4f415af56b06f1f38d5a0339dd9828ff136b115/" &&
  apt source libc6 && cd ../c74e800dfd5f72649d673b44292f4a817e45150b/ &&
  apt source libglib2.0-0; }

5. dir
${HOME}/.cache/debuginfod_client/a4f415af56b06f1f38d5a0339dd9828ff136b115/glibc-2.35

6. dir
${HOME}/.cache/debuginfod_client/c74e800dfd5f72649d673b44292f4a817e45150b/glib2.0-2.72.4

7. detach and attach

8. up

Expected result:
4518          ret = (*poll_func) (fds, n_fds, timeout);

Actual result:
Continuing without source file ./debian/build/deb/../../../glib/gmain.c.
4518    ../../../glib/gmain.c: No such file.

Work-around:
{ install -d
"${HOME}/.cache/debuginfod_client/c74e800dfd5f72649d673b44292f4a817e45150b/glib2.0-2.72.4/debian/build/deb";
}

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[Bug gdb/31088] gdb requires build directories to exist

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31088

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-11-29
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
                 CC|                            |fche at redhat dot com

--- Comment #1 from Frank Ch. Eigler <fche at redhat dot com> ---
Some baby investigation with ubuntu 22.04 binaries, taking /bin/ls
as an example:

eu-readelf -w `debuginfod-find debuginfo /bin/ls`:

DWARF section [30] '.debug_info' at offset 0x438:
 [Offset]
 Compilation unit at offset 0:
 Version: 5, Abbreviation section offset: 4084, Address size: 8, Offset size: 4
 Unit type: partial (3)
 [     c]  partial_unit         abbrev: 50
           stmt_list            (sec_offset) 0
           comp_dir             (line_strp) "."


 Compilation unit at offset 3348:
 Version: 5, Abbreviation section offset: 0, Address size: 8, Offset size: 4
 Unit type: compile (1)
 [   d20]  compile_unit         abbrev: 43
           producer             (GNU_strp_alt) "GNU GIMPLE 11.2.0
-mtune=generic -march=x86-64 -g -g -O2 -O2 -fno-openmp -fno-openacc -fPIC
-fcf-protection=full -fstack-protector-strong -ffat-lto-objects -fltrans"
           language             (data1) C11 (29)
           name                 (line_strp) "<artificial>"
           comp_dir             (line_strp) "."


i.e., AT_comp_dir = "."

MJW advises this implicates https://dwarfstd.org/issues/210628.1.html ,
wherein it is acknowledged that absolute paths are expected, and offers
semantics to DWARF6 for special cases.  Those special cases would not
help at all in the debuginfod-supplied cases, where the file names in
the client cache have no relationship to the build system's file tree
or the installed location of the binary.

So the question is why are these binaries arriving with ".", seeing that
they were produced by GCC.

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[Bug gdb/31088] gdb requires build directories to exist

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31088

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at klomp dot org

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[Bug gdb/31088] gdb requires build directories to exist

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31088

--- Comment #2 from Mark Wielaard <mark at klomp dot org> ---
In particular the latest draft (note draft! can still change!)
https://snapshots.sourceware.org/dwarfstd/dwarf-spec/latest/
says:

--- DRAFT ---

A DW_AT_comp_dir attribute whose value is a null-terminated string containing
the current working directory of the compilation command that produced this
compilation unit in whatever form makes sense for the host system.

If a relative path is used in DW_AT_comp_dir, it will be relative to the
location of the linked image containing the DW_AT_comp_dir entry.

In some cases a producer may allow the user to specify a relative path for
DW_AT_comp_dir. There are a few cases in which this is useful, but in general
using a relative path for DW_AT_comp_dir is discouraged as it will not work
well in many cases including the following: different relative paths are used
within the same build; the build system creates multiple linked images in
different directories; the final linked image is moved before being debugged; .o
files that need to be debugged directly.

--- DRAFT ---

So that seems to imply that you really shouldn't use relative paths (like "."),
unless you can make sure that when the image or source files are moved (or the
DWARF is put into a separate .debug file) like when doing make install, all the
relative are updated/resolved/rewritten.

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[Bug gdb/31088] gdb requires build directories to exist

[amerey at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31088

Aaron Merey <amerey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amerey at redhat dot com
             Status|NEW                         |RESOLVED
         Resolution|---                         |NOTABUG

--- Comment #3 from Aaron Merey <amerey at redhat dot com> ---
Closing this as NOTABUG. The query fails due to the presence of a relative
pathname in the debuginfo (./debian/build/deb/...). Debuginfod can only perform
source file queries on absolute pathnames.

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