end(3) [osx man page]

GET_END(3)						     Library Functions Manual							GET_END(3)

NAME

       get_end, get_etext, get_edata - get values of UNIX link editor defined symbols

SYNOPSIS

       #include <mach-o/getsect.h>

       unsigned long get_end();
       unsigned long get_etext();
       unsigned long get_edata();

DESCRIPTION

       These routines provide a stopgap measure to programs that use the UNIX link-editor defined symbols.  Use of these routines is very strongly
       discouraged.  The problem is that any program that is using UNIX link editor defined symbols (_end, _etext or _edata) is making assumptions
       that the program has the memory layout of a UNIX program.

       This is an incorrect assumption for a program built by the Mach-O link editor.  The reason that these routines are provided is that if very
       minimal assumptions about the layout are used and the default format and memory layout of the Mach-O link editor is used to build the  pro-
       gram,  some things may work by using the values returned by these routines in place of the addresses of their UNIX link-editor defined sym-
       bols.  So use at your own risk, and only if you know what your doing.  Or better yet, convert the program to use the  appropriate  Mach	or
       Mach-O  functions.   If	you  are  trying to allocate memory use vm_allocate(2), if you are trying to find out about your address space use
       vm_region(2) and if you are trying to find out where your program is loaded use the dyld(3) functions.

       The values of the UNIX link-editor defined symbols _etext, _edata and _end are returned by the routines get_etext, get_edata,  and  get_end
       respectively.  In a Mach-O file they have the following values: get_etext returns the first address after the (__TEXT,__text) section, note
       this my or may not be the only section in the __TEXT segment.  get_edata returns the first address after the (__DATA,__data) section,  note
       this  my  or  may not be the last non-zero fill section in the __DATA segment.  get_end returns the first address after the last segment in
       the executable, note a shared library may be loaded at this address.

SEE ALSO

       ld(1), dyld(3)

Apple Computer, Inc.						  April 10, 1998							GET_END(3)

MACH-O(5)							File Formats Manual							 MACH-O(5)

NAME

       Mach-O - Mach-O assembler and link editor output

SYNOPSIS

       #include <mach-o/loader.h>
       #include <mach-o/nlist.h>
       #include <mach-o/stab.h>
       #include <mach-o/reloc.h>

DESCRIPTION

       The  object  files  produced  by the assembler and link editor are in Mach-O (Mach object) file format.	The file name a.out is the default
       output file name of the assembler as(1) and the link editor ld(1) The format of the object file however is not 4.3BSD a.out format  as  the
       name  suggests,	but  rather  Mach-O  format.  The link editor will make a.out executable if the resulting format is an executable type and
       there were no errors and no unresolved external references.

       The complete description of a Mach-O file is given in a number of include files.  The file <mach-o/loader.h> describes the headers,  <mach-
       o/nlist.h> describes the symbol table entries with <mach-o/stab.h> supplementing it, and <mach-o/reloc.h> describes the relocation entries.

       The  actual  instructions and data used by the program represented by a Mach-O file are the contents of its sections.  Sections are grouped
       together in segments.  Each section carries with it, in its header, the information as to which segment it belongs in.  When  a	file  type
       that  is  executable  is  created  the sections are placed in their proper segment and all the segment headers are created and the segments
       themselves are padded out to the segment alignment (typically the target pagesize).  For the object file type produced by an assembler  (or
       by the link editor for further linking) all the sections are placed in one segment for compactness.

       When  the  kernel executes a Mach-O file it maps in the object file's segments, the dynamic link editor (if used) and creates the thread(s)
       for execution.  Any part of the object file that is not part of a segment is not mapped in for execution.  For executable using the dynamic
       link  editor  the  headers  and other link edit information is needed to execute the file.  These parts include the relocation entries, the
       symbol table and the string table.  These parts are mapped in with the use of the link editor's -seglinkedit option which creates a segment
       that contains these parts.  These parts can be stripped down with the -S option to ld(1) or various options to strip(1).

SEE ALSO

       as(1), ld(1), nm(1), gdb(1), stab(5), strip(1)

Apple Computer, Inc.						 October 22, 2001							 MACH-O(5)