[Bug default/26568] New: abidw lost anonymous member

[Bug default/26568] New: abidw lost anonymous member

[gprocida+abigail at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

            Bug ID: 26568
           Summary: abidw lost anonymous member
           Product: libabigail
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: default
          Assignee: dodji at redhat dot com
          Reporter: gprocida+abigail at google dot com
                CC: libabigail at sourceware dot org
  Target Milestone: ---

This is a fairly small C test case. I'

struct A {
  union {
    struct {
      int x;
    };
    struct {
      long y;
    };
  };
};

void fun(struct A * a) {
  a->x = 0;
  a->y = 0x0102030405060708ULL;
}

Compiling with GCC 9.3.0 and extracting the ABI with abidw results in the loss
of the member variable y (which dwarfdump confirms is present in the object
file).

Here's an even smaller test case:

union A {
  struct {
    int x;
  };
  struct {
    long y;
  };
};

void fun(union A * a) {
  a->x = 0;
  a->y = 0x0102030405060708ULL;
}

The very similar code below seems to be treated properly:

struct A {
  union {
    int x;
  };
  union {
    long y;
  };
};

void fun(struct A * a) {
  a->x = 0;
  a->y = 0x0102030405060708ULL;
}

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[Bug default/26568] abidw lost anonymous member

[gprocida+abigail at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

--- Comment #1 from Giuliano Procida <gprocida+abigail at google dot com> ---
The second anonymous member appears to be lost due this check in
add_or_update_union_type in the DWARF reader.

              if (lookup_var_decl_in_scope(n, result))                          
                continue;                                                       

Here n is the empty string for both members.

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[Bug default/26568] abidw lost anonymous member

[gprocida+abigail at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

--- Comment #2 from Giuliano Procida <gprocida+abigail at google dot com> ---
I have a rough fix at
https://github.com/myxoid/libabigail/commits/anon-member-trouble.

Next step is to see what difference it makes to kernel ABIs. It depends how
often we have anonymous structs inside unions.

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[Bug default/26568] abidw lost anonymous member

[gprocida+abigail at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

--- Comment #3 from Giuliano Procida <gprocida+abigail at google dot com> ---
W.r.t. kernel ABI:

The rough fix causes member-type elements to move out of the relevant unions.
It also results in a massive number of "harmless" diffs.

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[Bug default/26568] abidw lost anonymous member

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

dodji at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-09-15
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

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[Bug default/26568] A union can't have more than one anonymous member and that's wrong

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

dodji at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|abidw lost anonymous member |A union can't have more
                   |                            |than one anonymous member
                   |                            |and that's wrong

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[Bug default/26568] A union can't have more than one anonymous member and that's wrong

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

--- Comment #4 from dodji at redhat dot com ---
A patch for this has been submitted at
https://sourceware.org/pipermail/libabigail/2020q3/002668.html.

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[Bug default/26568] A union can't have more than one anonymous member and that's wrong

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26568

dodji at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from dodji at redhat dot com ---
The patch was applied to the master branch at
https://sourceware.org/git/?p=libabigail.git;a=commit;h=59610d5572bf8a997b0f490cae20d42f73acf3e1
and should be available in the 1.8 version of libabigail.

Thanks for reporting the issue and sorry for the inconvenience.

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