[Bug debug/9509] Incorrect function end in DWARF2 .debug_line section

["carlo at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=9509


carlo at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |carlo at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED


------- Additional Comments From carlo at gcc dot gnu dot org  2003-10-16 01:28 -------
This seems to be a bug in GNU as.  I am investigating this now and will
close the PR once I am 100% sure it is in as and not gcc.

The version of 'objdump' that I have installed today (version GNU objdump
2.13.90.0.20 20030319) behaves slightly different, but 'as' version
2.13.90.0.20 20030319 still shows the same behaviour.  It is just harder
to find though (I need my own 'libcwd' library to detect where the problem
is).  For example:

(Running test application linked with libcwd:

BFD     :     Loading debug info from
/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6...
<unfinished>
[...]
BFD     : |        42c1b - 42c35;
/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/include/ext/pool_allocator.h:273
: "-DWARF symbol"..
BFD     : |        WARNING: Different start for same function (42c30 - 42c47;
/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/include/ext/pool_allocator.h:279
: "-DWARF symbol"..)!?

The ranges 42c1b - 42c35 and 42c30 - 42c47 overlap thus, and we
know that probably the end of the first range is wrong.  The source
code at pool_allocator.h:273 till 279 reads:

      return __result;
    }

  template<bool __threads, int __inst>
    void*
    __pool_alloc<__threads, __inst>::allocate(size_t __n)
    {

So this is indeed the end of one function and the start of a next.
The first function (of which we now only see the end) starts at
line 245:

  template<bool __threads, int __inst>
    void*
    __pool_alloc<__threads, __inst>::_S_refill(size_t __n)
    {    <-- line 245

and from the same libcwd output we find that this corresponds with
the range:

BFD     : |        42ba0 - 42bac;
/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/include/ext/poo
l_allocator.h:245 : "-DWARF symbol"..

where 42ba0 then must be the start of this function.
With 'nm' we then find:

nm
/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6
| grep 42ba0
00042ba0 W _ZN9__gnu_cxx12__pool_allocILb1ELi0EE9_S_refillEj

and indeed, this is the correct function:

c++filt _ZN9__gnu_cxx12__pool_allocILb1ELi0EE9_S_refillEj
__gnu_cxx::__pool_alloc<(bool)1, (int)0>::_S_refill(unsigned)

Now we can look at the end of this function in the objdump, and
that start of the NEXT function, to find:

/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/include/ext/pool_allocator.h:273
   42c1b:       8b 45 ec                mov    0xffffffec(%ebp),%eax
   42c1e:       83 c4 1c                add    $0x1c,%esp
   42c21:       5b                      pop    %ebx
   42c22:       5e                      pop    %esi
   42c23:       5f                      pop    %edi
   42c24:       5d                      pop    %ebp
   42c25:       c3                      ret
   42c26:       90                      nop
   42c27:       90                      nop
   42c28:       90                      nop
   42c29:       90                      nop
   42c2a:       90                      nop
   42c2b:       90                      nop
   42c2c:       90                      nop
   42c2d:       90                      nop
   42c2e:       90                      nop
   42c2f:       90                      nop

00042c30 <_ZN9__gnu_cxx12__pool_allocILb1ELi0EE8allocateEj>:
_ZN9__gnu_cxx12__pool_allocILb1ELi0EE8allocateEj():
/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/include/ext/pool_allocator.h:279
   42c30:       55                      push   %ebp
   42c31:       89 e5                   mov    %esp,%ebp
   42c33:       83 ec 38                sub    $0x38,%esp
/usr/src/GNU/builds-gcc/PR9509/PR9509-native/i686-pc-linux-gnu/libstdc++-v3/include/ext/pool_allocator.h:273
   42c36:       89 5d f4                mov    %ebx,0xfffffff4(%ebp)

Where the last 'pool_allocator.h:273' is wrongly inserted as a result
of the end of the previous function being 'pushed in'.
However, the start of this function is now showed correctly.