[lldb-dev] .ctors / .init_array sections

Michael Sartain mikesart at gmail.com
Tue Aug 13 11:45:41 PDT 2013

When I build a simple hello world sample on i386 and x64 on Linux with
Clang 3.3, the x64 version has .init_array / .fini_array and the i386
binary has .ctors / .dtors.

  [18] .ctors            PROGBITS
  [19] .dtors            PROGBITS

  [18] .init_array       INIT_ARRAY
  [19] .fini_array       FINI_ARRAY

There is code in ObjectFileELF.cpp which specifically looks for sections
named ".ctors" and ".dtors" and sets the symbol type to eSymbolTypeCode if
it not already set. There is no check for init_array there. That means the
x64 version lists these symbols as Invalid currently.

(lldb) target modules dump symtab hello_world

[   17]     Code          __init_array_end
[   18]     Code          __init_array_start

[   17]     Invalid       __init_array_end
[   18]     Invalid       __init_array_start

I believe the fix is to add a check for init_array + fini_array and mark
those sections as code. If anyone has any knowledge / comments on this,
please fire away, otherwise I'll post a patch in the next couple days.

There are also some sections in both i386 and x64 that are being marked as
undefined. I assume this is ok?

[   24]     55     Undefined    0x0000000000000000
 0x0000000000000000 0x00000020 __gmon_start__
[   25]     56     Undefined    0x0000000000000000
 0x0000000000000000 0x00000020 _Jv_RegisterClasses
[   28]     59   X Undefined    0x0000000000000000
 0x0000000000000000 0x00000012 __libc_start_main@@GLIBC_2.0

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