[llvm-dev] [LLD] Is there any reason to add _GLOBAL_OFFSET_TABLE_ to .dynsym?

Simon Atanasyan via llvm-dev llvm-dev at lists.llvm.org
Mon Feb 8 06:22:03 PST 2016


When LLD builds a shared library for x86_64 it puts
_GLOBAL_OFFSET_TABLE_ to the both .symtab and .dynsym and defines it
as a GLOBAL symbol. If later this shared library participates in
executable file linking and GNU BFD linked is used for that, this
linker shows an error:

/usr/bin/ld: a.out: hidden symbol `_GLOBAL_OFFSET_TABLE_' in
/usr/lib/x86_64-linux-gnu/crt1.o is referenced by DSO

Gold linker does not show any error, but it is anyway strange that we
make _GLOBAL_OFFSET_TABLE_ globally visible and add it to dynamic
symbol table.

Both BFD and Gold linker do not put _GLOBAL_OFFSET_TABLE_ to the
dynamic symbol table and defines this symbol as follows:

BFD:
Num:    Value          Size Type    Bind   Vis      Ndx Name
 42: 0000000000200990     0 OBJECT  LOCAL  DEFAULT  ABS _GLOBAL_OFFSET_TABLE_

Gold:
Num:    Value          Size Type    Bind   Vis      Ndx Name
 19: 0000000000001a18    40 OBJECT  LOCAL  HIDDEN    19 _GLOBAL_OFFSET_TABLE_

-- 
Simon Atanasyan


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