bfd: GLOBAL HIDDEN reloc zeroed out when -lc

[John Reiser]

Hi,

version: both binutils-2.11 and binutils-2.10.1, on i686-pc-linux-gnu.

Running  "ld-new -m elf_i386 -o foo.so crtbeginS.o"
correctly relocates the R_386_GOT32 reference and R_386_32
target datum __dso_handle (which points to itself) of
routine __do_global_dtors_aux .

Running  "ld-new -m elf_i386 -o foo.so crtbeginS.o -lc"
(same except for "-lc") results in __dso_handle containing zero,
and leaving a R_386_NONE relocation in .rel.got.
The NONE relocation is harmless, but perhaps symptomatic.
__dso_handle containing 0 is a bug.

crtbeginS.o is commonly found in /usr/lib/gcc-lib/<platform>/<release> ;
I attach a .tar.gz copy of mine.  Yes, there is no "-shared" parameter.
This is somewhat unusual, but the R_386_32 relocation still should work.


Here is my diagnostic info:
$ readelf --all crtbeginS.o
        ...
Relocation section '.rel.text' at offset 0x7d4 contains 17 entries:
  Offset    Info  Type            Symbol's Value  Symbol's Name
        ...
  0000002c  01803 R_386_GOT32           00000000  __dso_handle
        ...

Relocation section '.rel.data' at offset 0x85c contains 2 entries:
  Offset    Info  Type            Symbol's Value  Symbol's Name
  00000000  01801 R_386_32              00000000  __dso_handle
        ...

Symbol table '.symtab' contains 29 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
        ...
    24: 00000000     0 OBJECT  GLOBAL HIDDEN    3 __dso_handle
        ...

-----without -lc; relocation OK
$ ld-new -m elf_i386 -o foo.so crtbeginS.o
$ gdb foo.so
(gdb) x/14i __do_global_dtors_aux
0x8048084 <__do_global_dtors_aux>:      push   %ebp
0x8048085 <__do_global_dtors_aux+1>:    mov    %esp,%ebp
0x8048087 <__do_global_dtors_aux+3>:    push   %ebx
0x8048088 <__do_global_dtors_aux+4>:    sub    $0x4,%esp
0x804808b <__do_global_dtors_aux+7>:    call   0x8048080
0x8048090 <__do_global_dtors_aux+12>:   add    $0x1104,%ebx
0x8048096 <__do_global_dtors_aux+18>:   mov    0xfffffff4(%ebx),%eax
0x804809c <__do_global_dtors_aux+24>:   test   %eax,%eax
0x804809e <__do_global_dtors_aux+26>:
    jne    0x804810e <__do_global_dtors_aux+138>
0x80480a0 <__do_global_dtors_aux+28>:   mov    0xc(%ebx),%ecx
0x80480a6 <__do_global_dtors_aux+34>:   test   %ecx,%ecx
0x80480a8 <__do_global_dtors_aux+36>:
    je     0x80480be <__do_global_dtors_aux+58>
0x80480aa <__do_global_dtors_aux+38>:   mov    0x10(%ebx),%eax  # %eax is OK
0x80480b0 <__do_global_dtors_aux+44>:   sub    $0xc,%esp

(gdb) x/x 0x8048090+0x1104+0x10
0x80491a4 <_GLOBAL_OFFSET_TABLE_+16>:   0x08049180   # value loaded ino %eax
-----

-----with -lc; relocated datum is zero
$ ld-new -m elf_i386 -o foo.so crtbeginS.o -lc
$ gdb foo.so
(gdb) x/14i __do_global_dtors_aux
0x8048274 <__do_global_dtors_aux>:      push   %ebp
0x8048275 <__do_global_dtors_aux+1>:    mov    %esp,%ebp
0x8048277 <__do_global_dtors_aux+3>:    push   %ebx
0x8048278 <__do_global_dtors_aux+4>:    sub    $0x4,%esp
0x804827b <__do_global_dtors_aux+7>:    call   0x8048270 <__cxa_finalize+28>
0x8048280 <__do_global_dtors_aux+12>:   add    $0x1104,%ebx
0x8048286 <__do_global_dtors_aux+18>:   mov    0xfffffff4(%ebx),%eax
0x804828c <__do_global_dtors_aux+24>:   test   %eax,%eax
0x804828e <__do_global_dtors_aux+26>:
    jne    0x80482fe <__do_global_dtors_aux+138>
0x8048290 <__do_global_dtors_aux+28>:   mov    0x24(%ebx),%ecx
0x8048296 <__do_global_dtors_aux+34>:   test   %ecx,%ecx
0x8048298 <__do_global_dtors_aux+36>:
    je     0x80482ae <__do_global_dtors_aux+58>
0x804829a <__do_global_dtors_aux+38>:   mov    0x1c(%ebx),%eax  # %eax is 0; 
<<bug>>
0x80482a0 <__do_global_dtors_aux+44>:   sub    $0xc,%esp

(gdb) x/x 0x8048280+0x1104+0x1c
0x80493a0 <_GLOBAL_OFFSET_TABLE_+28>:   0x00000000   # value loaded into %eax
-----

-- 
John Reiser, address@hidden

crtbeginS.tar.gz
Description: Binary data