# (ld) Output Section Keywords

(ld) Output Section Data (ld) SECTIONS (ld) Output Section Discarding

     Output section keywords
     -----------------------

     There are a couple of keywords which can appear as output section
     commands.

     `CREATE_OBJECT_SYMBOLS'
          The command tells the linker to create a symbol for each input
          file.  The name of each symbol will be the name of the
          corresponding input file.  The section of each symbol will be the
          output section in which the `CREATE_OBJECT_SYMBOLS' command
          appears.

          This is conventional for the a.out object file format.  It is not
          normally used for any other object file format.

     `CONSTRUCTORS'
          When linking using the a.out object file format, the linker uses an
          unusual set construct to support C++ global constructors and
          destructors.  When linking object file formats which do not support
          arbitrary sections, such as ECOFF and XCOFF, the linker will
          automatically recognize C++ global constructors and destructors by
          name.  For these object file formats, the `CONSTRUCTORS' command
          tells the linker to place constructor information in the output
          section where the `CONSTRUCTORS' command appears.  The
          `CONSTRUCTORS' command is ignored for other object file formats.

          The symbol `__CTOR_LIST__' marks the start of the global
          constructors, and the symbol `__DTOR_LIST' marks the end.  The
          first word in the list is the number of entries, followed by the
          address of each constructor or destructor, followed by a zero
          word.  The compiler must arrange to actually run the code.  For
          these object file formats GNU C++ normally calls constructors from
          a subroutine `__main'; a call to `__main' is automatically
          inserted into the startup code for `main'.  GNU C++ normally runs
          destructors either by using `atexit', or directly from the function
          `exit'.

          For object file formats such as `COFF' or `ELF' which support
          arbitrary section names, GNU C++ will normally arrange to put the
          addresses of global constructors and destructors into the `.ctors'
          and `.dtors' sections.  Placing the following sequence into your
          linker script will build the sort of table which the GNU C++
          runtime code expects to see.

                     __CTOR_LIST__ = .;
                     LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
                     *(.ctors)
                     LONG(0)
                     __CTOR_END__ = .;
                     __DTOR_LIST__ = .;
                     LONG((__DTOR_END__ - __DTOR_LIST__) / 4 - 2)
                     *(.dtors)
                     LONG(0)
                     __DTOR_END__ = .;

          If you are using the GNU C++ support for initialization priority,
          which provides some control over the order in which global
          constructors are run, you must sort the constructors at link time
          to ensure that they are executed in the correct order.  When using
          the `CONSTRUCTORS' command, use `SORT(CONSTRUCTORS)' instead.
          When using the `.ctors' and `.dtors' sections, use
          `*(SORT(.ctors))' and `*(SORT(.dtors))' instead of just
          `*(.ctors)' and `*(.dtors)'.

          Normally the compiler and linker will handle these issues
          automatically, and you will not need to concern yourself with
          them.  However, you may need to consider this if you are using C++
          and writing your own linker scripts.

(ld) Output Section Data (ld) SECTIONS (ld) Output Section Discarding

automatically generated by info2html