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END(3)                     Linux Programmer's Manual                    END(3)



 

NAME


       etext, edata, end - end of program segments

 

SYNOPSIS


       extern etext;
       extern edata;
       extern end;

 

DESCRIPTION






       The addresses of these symbols indicate the end of various program seg-
       ments:

       etext  This is the first address past the end of the text segment  (the
              program code).

       edata  This  is  the first address past the end of the initialized data
              segment.

       end    This is the first address past the end of the uninitialized data
              segment (also known as the BSS segment).

 

CONFORMING TO


       Although  these  symbols  have long been provided on most Unix systems,
       they are not standardized; use with caution.

 

NOTES


       The program must explicitly declare these symbols; they are not defined
       in any header file.

       On some systems the names of these symbols are preceded by underscores,
       thus: _etext, _edata, and _end.  These symbols  are  also  defined  for
       programs compiled on Linux.

       At  the start of program execution, the program break will be somewhere
       near &end (perhaps at the start of the following page).   However,  the
       break  will change as memory is allocated via brk(2) or malloc(3).  Use
       sbrk(2) with an argument of zero to find the current value of the  pro-
       gram break.

 

EXAMPLE


       When run, the program below produces output such as the following:

           $ ./a.out
           First address past:
               program text (etext)       0x8048568
               initialized data (edata)   0x804a01c
               uninitialized data (end)   0x804a024

       #include 
       #include 

       extern char etext, edata, end; /* The symbols must have some type,
                                          or "gcc -Wall" complains */

       int
       main(int argc, char *argv[])
       {
           printf("First address past:\n");
           printf("    program text (etext)      %10p\n", &etext);
           printf("    initialized data (edata)  %10p\n", &edata);
           printf("    uninitialized data (end)  %10p\n", &end);

           exit(EXIT_SUCCESS);
       }

 

SEE ALSO


       objdump(1), readelf(1), sbrk(2), elf(5)

 

COLOPHON


       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2008-07-17                            END(3)