[Bug default/24430] reader: fold away const for array types

[Bug default/24430] reader: fold away const for array types

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=24430

dodji at redhat dot com changed:

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

--- Comment #3 from dodji at redhat dot com ---
This issue should be fixed in the master branch of the git repository by commit
https://sourceware.org/git/gitweb.cgi?p=libabigail.git;a=commit;h=286cadf8419e00f9efbcbf3b15670eb50982a31f.

You can either get that fix from the development tree out of git and build it
yourself, or wait for the 1.7 version of libabigail to be released and get it
from there.

In any case, thank you for taking the time to submit this problem and sorry for
the inconvenience.

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[Bug default/24430] reader: fold away const for array types

[maennich at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=24430

--- Comment #2 from Matthias Maennich <maennich at google dot com> ---
Created attachment 11729
  --> https://sourceware.org/bugzilla/attachment.cgi?id=11729&action=edit
Clang compiled

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[Bug default/24430] reader: fold away const for array types

[maennich at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=24430

--- Comment #1 from Matthias Maennich <maennich at google dot com> ---
Created attachment 11728
  --> https://sourceware.org/bugzilla/attachment.cgi?id=11728&action=edit
GCC compiled

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[Bug default/24430] reader: fold away const for array types

[dodji at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=24430

dodji at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2019-04-09
     Ever confirmed|0                           |1

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[Bug default/24430] New: reader: fold away const for array types

[maennich at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=24430

            Bug ID: 24430
           Summary: reader: fold away const for array types
           Product: libabigail
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: default
          Assignee: dodji at redhat dot com
          Reporter: maennich at google dot com
                CC: libabigail at sourceware dot org
  Target Milestone: ---

Created attachment 11727
  --> https://sourceware.org/bugzilla/attachment.cgi?id=11727&action=edit
test.c

Given the following example:

struct test {
  const char asdf[4];
};

void func(struct test arg) {}


The C standard seems to allow two representations for 'asdf' here:
  const char[]   and   const char[] const

"If  the  specification  of  an  array  type  includes  any type  qualifiers, 
the  element  type  is  so-qualified,  not  the  array  type."

In fact, clang and gcc seem to disagree here as well and produce the following
dwarf info:

 clang: asdf -> array_type -> const_type -> signed char
 gcc:   asdf -> const_type -> array_type -> const_type -> signed char

That upsets libabigail when comparing the ABI of two sample builds:

1 function with some indirect sub-type change:

  [C]'function void func(test)' at test.c:5:1 has some indirect sub-type
changes:
    parameter 1 of type 'struct test' has sub-type changes:
      type size hasn't changed
      1 data member change:
       type of 'const char test::asdf[4]' changed:
         entity changed from 'const char[4]' to 'const char[4] const'



Reproducer:
 $ clang-7 -g -gdwarf-2 -shared test.c -o clang.out 
 $ gcc -g -gdwarf-2 -shared test.c -o gcc.out
 $ abidiff clang.out gcc.out

I attach a set of binaries.

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