c++_eoe Release Notes

A Dynamic Shared Objects

 



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       1.  Introduction

       These notes describe the C++ Translator Execution
       Environment (c++_eoe) from Silicon Graphics, Inc.  The C++
       Translator EOE contains C++ libraries supplied as DSOs
       (dynamic shared objects).  DSOs are discussed in Appendix A
       and in the dso(5) man page.

       Note:  Packaged with this software is a separate sheet that
              contains the Software License Agreement.  This
              software is provided to you solely under the terms
              and conditions of the Software License Agreement.
              Please take a few moments to review the Agreement.

       1.1  C++_Applications_Prerequisite

       If you plan to run any C++-based applications, it is
       important to note that you must install the C++ Translator
       EOE.



       1.2  Release_Identification_Information

       Following is the release identification information for the
       C++ Translator Execution Environment (c++_eoe):

       Software Product               C++ EOE

       Version                        3.2.1
       System Software Requirements   IRIX 5.2

       1.3  3.2.1_C++_Translator_Execution_Environment_Subsystems

       The 3.2.1 C Compiler EOE software (c++_eoe) includes these
       subsystems:

       c++_eoe                    Standard C++ execution
                                  environment

       c++_eoe.sw                 Standard C++ execution software

       c++_eoe.sw.lib             Standard C++ execution libraries

       1.4  Online_Release_Notes

       After you install the online documentation for a product
       (the relnotes subsystem), you can view the release notes on
       your screen.













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       If you have a graphics system, select ``Release Notes'' from
       the Tools submenu of the Toolchest. This displays the
       grelnotes(1) graphical browser for the online release notes.

       Refer to the grelnotes(1) man page for information on
       options to this command.

       If you have a nongraphics system, you can use the relnotes
       command.  Refer to the relnotes(1) man page for accessing
       the online release notes.

       1.5  Product_Support

       Silicon Graphics, Inc., provides a comprehensive product
       support maintenance program for its products.

       If you are in the U.S. or Canada and would like support for
       your Silicon Graphics-supported products, contact the
       Technical Assistance Center at 1-800-800-4SGI.  If you are
       outside these areas, contact the Silicon Graphics subsidiary
       or authorized distributor in your country.






































 



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       1.  Dynamic_Shared_Objects

       A Dynamic Shared Object, or DSO, is an ELF format object
       file, very similar in structure to an executable program but
       with no "main".  It has a shared component, consisting of
       shared text and read-only data; a private component,
       consisting of data and the GOT (Global Offset Table);
       several sections that hold information necessary to load and
       link the object; and a liblist, the list of other shared
       objects referenced by this object. Most of the libraries
       supplied by SGI are available as dynamic shared objects.

       A DSO is relocatable at runtime; it can be loaded at any
       virtual address.  A consequence of this is that all
       references to external symbols must be resolved at runtime.
       References from the private region (.e.g. from private data)
       are resolved once at load-time; references from the shared
       region (e.g. from shared text) must go through an
       indirection table (GOT) and hence have a small performance
       penalty associated with them.

       Code compiled for use in a shared object is referred to as
       Position Independent Code (PIC), whereas non-PIC is usually
       referred to as non-shared.  Non-shared code and PIC cannot
       be mixed in the same object.

       At Runtime, exec loads the main program and then loads rld,
       the runtime linking loader, which finishes the exec
       operation.  Starting with main's liblist, rld loads each
       shared object on the list, reads that object's liblist, and
       repeats the operation until all shared objects have been
       loaded.  Next, rld allocates common and fixes up symbolic
       references in each loaded object.  (This is necessary
       because we don't know until runtime where the object will be
       loaded.)  Next, each object's init code is executed.
       Finally, control is transferred to "__start".

       For a more complete discussion of DSOs, including answers to
       questions frequently asked about them, see the dso(5) man
       page.