конец программных сегментов (end of program segments)
Имя (Name)
etext, edata, end - end of program segments
Синопсис (Synopsis)
extern etext;
extern edata;
extern end;
Описание (Description)
The addresses of these symbols indicate the end of various
program segments:
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).
Стандарты (Conforming to)
Although these symbols have long been provided on most UNIX
systems, they are not standardized; use with caution.
Примечание (Note)
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 program break.
Примеры (Examples)
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
Program source
#include <stdio.h>
#include <stdlib.h>
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);
}
Смотри также (See also)
objdump(1), readelf(1), sbrk(2), elf(5)
