[Bug 1848211] Re: valgrind fails to use debug symbols from glib/gtk

[Balint Reczey]

The problematic debug symbol files triggering the valgrind issue.

root at ee:~# readelf --debug-dump=links /usr/lib/x86_64-linux-gnu/libgmodule-2.0.so.0.6200.1
Contents of the .gnu_debugaltlink section:

  Separate debug info file: /usr/lib/debug/.dwz/x86_64-linux-gnu/libglib2.0-0.debug
  Build-ID (0x14 bytes):
 cb 51 16 ac 07 e2 cb 3d 10 5e 39 f1 63 ba b7 b1 45 94 a1 49

Contents of the .gnu_debuglink section:

  Separate debug info file: 73a7789b7bf820c8546a35c13938e61fac4de0.debug
  CRC value: 0xc19e667a

root at ee:~# readelf --debug-dump=links /usr/lib/debug/.build-id/0f/73a7789b7bf820c8546a35c13938e61fac4de0.debug
readelf: Warning: Unsupported form (DW_FORM_GNU_strp_alt) for attribute DW_AT_comp_dir
Contents of the .gnu_debugaltlink section:

  Separate debug info file: /usr/lib/debug/.dwz/x86_64-linux-gnu/libglib2.0-0.debug
  Build-ID (0x14 bytes):
 cb 51 16 ac 07 e2 cb 3d 10 5e 39 f1 63 ba b7 b1 45 94 a1 49

root at ee:~# readelf --debug-dump=links /usr/lib/debug/.dwz/x86_64-linux-
gnu/libglib2.0-0.debug

.gnu_debuglink should not be present in
73a7789b7bf820c8546a35c13938e61fac4de0.debug.

** Description changed:

+ [Impact]
+ 
+  * With dwz the .gnu_debuglink section may appear duplicated in the
+ debug file referenced originally in the .gnu_debuglink section. In that
+ case Valgrind fails to load the debug symbols.
+ 
+ [Test Case]
+ 
+  * In Ubuntu releases earlier than 19.10 use gio from a package rebuilt with dwz.
+  * Observe no relevant error when running gio with valgrind: 
+    $ valgrind /usr/bin/gio ~
+ 
+ [Regression Potential]
+ 
+  * The fix is very simple, just ignoring the second .gnu_debuglink
+ found. There are no likely regressions.
+ 
+ [Original Bug Text]
+ 
  The debug symbols from libglib2.0-0-dbgsym and libgtk-3-0-dbgsym don't
  get properly picked up by valgrind in eoan for some reason. The symbols
  correctly work under gdb.
  
  There is an warning printed from valgrind
  'debuginfo section duplicates a section in the main ELF file'
  
  Laney tried to rebuild without dh_dwz and it makes the warning go away and the symbol work.
  Downgrading valgrind to the disco version doesn't fix the issue.

** Summary changed:

- valgrind fails to use debug symbols from glib/gtk
+ [SRU] valgrind fails to use debug symbols from glib/gtk

** Also affects: valgrind (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Also affects: valgrind (Ubuntu Disco)
   Importance: Undecided
       Status: New

** Changed in: valgrind (Ubuntu Bionic)
   Importance: Undecided => Low

** Changed in: valgrind (Ubuntu Disco)
   Importance: Undecided => Low

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https://bugs.launchpad.net/bugs/1848211

Title:
  [SRU] valgrind fails to use debug symbols from glib/gtk

Status in Valgrind:
  Confirmed
Status in valgrind package in Ubuntu:
  Triaged
Status in valgrind source package in Bionic:
  Triaged
Status in valgrind source package in Disco:
  Triaged
Status in valgrind source package in Eoan:
  Triaged
Status in valgrind source package in Focal:
  Triaged

Bug description:
  [Impact]

   * With dwz the .gnu_debuglink section may appear duplicated in the
  debug file referenced originally in the .gnu_debuglink section. In
  that case Valgrind fails to load the debug symbols.

  [Test Case]

   * In Ubuntu releases earlier than 19.10 use gio from a package rebuilt with dwz.
   * Observe no relevant error when running gio with valgrind: 
     $ valgrind /usr/bin/gio ~

  [Regression Potential]

   * The fix is very simple, just ignoring the second .gnu_debuglink
  found. There are no likely regressions.

  [Original Bug Text]

  The debug symbols from libglib2.0-0-dbgsym and libgtk-3-0-dbgsym don't
  get properly picked up by valgrind in eoan for some reason. The
  symbols correctly work under gdb.

  There is an warning printed from valgrind
  'debuginfo section duplicates a section in the main ELF file'

  Laney tried to rebuild without dh_dwz and it makes the warning go away and the symbol work.
  Downgrading valgrind to the disco version doesn't fix the issue.

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