[Bug default/18941] New: Add a warning option to libabigail tools to report possible DWARF issues

[Bug default/18941] New: Add a warning option to libabigail tools to report possible DWARF issues

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18941

            Bug ID: 18941
           Summary: Add a warning option to libabigail tools  to report
                    possible DWARF issues
           Product: libabigail
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: default
          Assignee: dodji at redhat dot com
          Reporter: dodji at redhat dot com
                CC: libabigail at sourceware dot org
  Target Milestone: ---

Sometimes it's interesting to raise awareness about some noticeable constructs
found in the debug information of the binary we are interested in.

For instance, there can be situations where a library does not have any debug
information for a class because the compiler knows that it will be emitted
along with the vtable in another library.  In that case, only a simple forward
declaration is found for the class in the current library.

This is fine for debugging, but interferes with ABI verification.

In this case, it would be useful that abidiff, abidw or other related tools
emit a clear diagnostic about the situation.  The library maintainer could deal
with the issue by using e.g the -femit-class-debug-always option of the G++
where she sees fit.

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[Bug default/18941] Add a warning option to libabigail tools to report possible DWARF issues

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18941

dodji at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

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[Bug default/18941] Add a warning option to libabigail tools to report possible DWARF issues

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18941

--- Comment #1 from dodji at redhat dot com ---
We'd also like to detect possible ODR violations, now that libabigail knows
about ODR (https://en.wikipedia.org/wiki/One_Definition_Rule).

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[Bug default/18941] Add a warning option to libabigail tools to report possible DWARF issues

[woodard at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18941

--- Comment #2 from Ben Woodard <woodard at redhat dot com> ---
Many of the cases which I think need warnings are more prosaic.

If it comes along a case where the DWARF has been stripped or was never
generated, then most if not all of the ABI verification is not being done. This
should be a higher priority warning. This could also remind people to point the
libabigail utilities toward an external debuginfo file. I would say that this
is a high enough priority that it should be the default unless some --quiet
option is passed on the command line.

A lower priority warning would be a exported function entry point for a
non-static function that exists in ELF but doesn't exist in the available
DWARF. This is important because we need to know the things that we are not yet
examining. I thought the option should be something like -Wunexamined-functions

A similar situation is the one you mention where you have a forward declaration
but no information about the class. -Wunexamined-classes

I think that -Wunions probably should be there too. This would trip if
libabigail found any unions in the DWARF and emit the union's name for manual
verification. I do not recall seeing this in the release notes. We should
probably have a note saying that unions are not examined for ABI compatibility
in the release notes.

And finally because the number of these warnings will likely grow over time we
should probably have something like:
-W which turns on common problems
-Wall which turns on every single warning.

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[Bug default/18941] Add a warning option to libabigail tools to report possible DWARF issues

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18941

dodji at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|                            |20937

--- Comment #3 from dodji at redhat dot com ---
(In reply to dodji from comment #1)
> We'd also like to detect possible ODR violations, now that libabigail knows
> about ODR (https://en.wikipedia.org/wiki/One_Definition_Rule).

I have filled enhancement request #20937 to track this specifically as it's a
request that has come up on several occasions.


Referenced Bugs:

https://sourceware.org/bugzilla/show_bug.cgi?id=20937
[Bug 20937] Detect ODR violations
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