Closure

The linker lists all the required objects under the closure section with the following details:

• Level of closure: Object B is in Object A's closure if and only if, the level of B is higher than the level of A and one of the following conditions is true:

  Condition 1: There is no object in between B and A.

  Condition 2: There are objects between B and A, and the level of A is lower than the levels of all the objects between B and A.

• Object name: specifies the name of an object.
• Object characteristics: specifies the characteristics of an object. They can be one of the following:
  • function, local | global | weak
  • section, local | global | weak
  • object, local | global | weak
  • notype, local | global | weak
• Object locations: specifies an object location.

The listing below shows a sample closure section.

1] reset (func,global) found in reset.o
 2] __reset (func,global) found in 8568mds_init.o 
  3] __start (func,global) found in Runtime.PPCEABI.E2.UC.a __start.o
   4] __init_registers (func,weak) found in Runtime.PPCEABI.E2.UC.a __start.o
    5] _stack_addr found as linker generated symbol
    5] _SDA2_BASE_ found as linker generated symbol
    5] _SDA_BASE_ found as linker generated symbol
   4] __init_hardware (func,global) found in __ppc_eabi_init.o 
    5] usr_init (func,global) found in 8568mds_init.o 
     6] gInterruptVectorTable (notype,global) found in eppc_exception.o 
      7] gInterruptVectorTableEnd (notype,global) found in eppc_exception.o 
      7] .intvec (section,local) found in eppc_exception.o 
       8] InterruptHandler (func,global) found in interrupt.o 
        9] @21 (object,local) found in interrupt.o 
        9] printf (func,global) found in MSL_C.PPCEABI.bare.E2.UC.a printf.o
         9] __msl_count_trailing_zero64 (func,weak) found in MSL_C.PPCEABI.bare.E.a 
math_double.o
        9] >>> UNREFERENCED DUPLICATE __msl_count_trailing_zero64
        9] >>> (func,weak) found in MSL_C.PPCEABI.bare.E.a math_float.o
        9] >>> (func,weak) found in MSL_C.PPCEABI.bare.E.a math_longdouble.o

         9] >>> (func,weak) found in MSL_C.PPCEABI.bare.E.a math_ppc.o

In the sample above:

• __reset is in the closure of reset because:
  • __reset is of level 2, reset is of level 1 and
  • there is no object in between __reset and reset
• _SDA_BASE_ is in the closure of __init_registers because:
  • _SDA_BASE_ is of level 5, __init_registers is of level 4; and
  • the objects between __init_registers and _SDA_BASE_ are all of level 5 and are higher than the level of __init_registers
• InterruptHandler is in the closure of __init_hardware because:
  • InterruptHandler is of level 8, __init_hardware is of level 4; and
  • the objects between __init_hardware and InterruptHandler are of level 5, 6, 7 respectively and are all higher than the level of __init_hardware
• __init_hardware is NOT in the closure of _init_registers because they both are of level 4
• gInterruptVectorTableEnd is NOT in the closure of __init_registers because:
  • the objects between gInterruptVectorTableEnd and __init_registers are not all of a higher level than __init_registers
  • __init_hardware is of the same level as __init_registers.

Weak symbols are allowed by the ABI and are global. They can have the same name as another symbol. The line before the UNREFERENCED DUPLICATE lists the first weak symbol found by the linker, that appears in the executable.

The line after the UNREFERENCED DUPLICATE lists other versions of a same object found by the linker. Linker will not copy the duplicate objects to the executable.