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etext(3) [freebsd man page]

END(3)							   BSD Library Functions Manual 						    END(3)

NAME
end, etext, edata -- end boundaries of image segments SYNOPSIS
extern end; extern etext; extern edata; DESCRIPTION
The globals end, etext and edata are program segment end addresses. etext is the first address after the end of the text segment. edata is the first address after the end of the initialized data segment. end is the first address after the end of the data segment (BSS) when the program is loaded. Use the sbrk(2) system call with zero as its argument to find the current end of the data segment. SEE ALSO
sbrk(2), malloc(3), a.out(5) HISTORY
An end manual page appeared in Version 6 AT&T UNIX. BUGS
Traditionally, no variable existed that pointed to the start of the text segment because the text segment always started at address zero. Although it is no longer valid to make this assumption, no variable similar to the ones documented above exists to point to the start of the text segment. BSD
August 28, 2000 BSD

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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 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). 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 program 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 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: "); printf(" program text (etext) %10p ", &etext); printf(" initialized data (edata) %10p ", &edata); printf(" uninitialized data (end) %10p ", &end); exit(EXIT_SUCCESS); } SEE ALSO
objdump(1), readelf(1), sbrk(2), elf(5) COLOPHON
This page is part of release 3.53 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)
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