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class Test
{
    public:
        Test()
        {
            mem = reinterpret_cast<unsigned short *>(0xB8000);

            * mem++ = 0x4041;
        }

        ~Test()
        {
            * mem++ = 0x4042;
        }
    private:
        unsigned short * mem;
};

Test test;

extern "C" unsigned long start_ctors, end_ctors, start_dtors, end_dtors;

extern "C" init(unsigned long magic, unsigned long addr)
{
    for(unsigned long * constructor(& start_ctors); constructor < & end_ctors; ++constructor)
        ((void (*) (void)) (*constructor)) ();

    // Kernel main

    for(unsigned long * destructor(& start_dtors); destructor < & end_dtors; ++destructor)
        ((void (*) (void)) (* destructor)) ();
}

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ENTRY(start)
SECTIONS
{
	.text 0x100000 :
	{
		code = .; _code = .; __code = .;
		*(.text*)
		*(.gnu.linkonce.t*)

		. = ALIGN(0x1000);
	}

	.rodata :
	{
		*(.rodata*)
		*(.rdata*)
		*(.gnu.linkonce.r*)

		. = ALIGN(0x1000);
	}

	.data :
	{
		data = .; _data = .; __data = .;
		*(.data*)
		*(.gnu.linkonce.d*)

		. = ALIGN(0x1000);
	}

	.ctors :
	{
		start_ctors = .; _start_ctors = .; __start_ctors = .;
		*(.ctor*)
		end_ctors = .; _end_ctors = .; __end_ctors = .;

		. = ALIGN(0x1000);
	}

	.dtors :
	{
		start_dtors = .; _start_dtors = .; __start_dtors = .;
		*(.dtor*)
		end_dtors = .; _end_dtors = .; __end_dtors = .;*/
	}

	.bss :
	{
		bss = .; _bss = .; __bss = .;

		*(.bss*)
		*(.gnu.linkonce.b*)

		. = ALIGN(0x1000);
	}

	end = .; _end = .; __end = .;
}

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There are 6 section headers, starting at offset 0x4024:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al

  [ 0]                   NULL            00000000 000000 000000 00      0   0  0

  [ 1] .text             PROGBITS        00100000 001000 001000 00  AX  0   0  4

  [ 2] .data             PROGBITS        00101000 002000 001000 00  WA  0   0  4

  [ 3] .ctors            PROGBITS        00102000 003000 001000 00  WA  0   0  4

  [ 4] .bss              NOBITS          00103000 004000 009000 00  WA  0   0 32

  [ 5] .shstrtab         STRTAB          00000000 004000 000023 00      0   0  1

Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

Code: Select all

#define ATEXIT_MAX_DESTRUCTORS			128

struct AtExit
{
	void (* func)(void *);
	void * obj;
};

static int atExitIndex = 0;
static AtExit atExitDestructors[ATEXIT_MAX_DESTRUCTORS];

extern "C" unsigned long start_ctors, end_ctors, start_dtors, end_dtors;

extern "C" void init(unsigned long magic, unsigned long addr)
{
	for(unsigned long * constructor(& start_ctors); constructor < & end_ctors; ++constructor)
		((void (*) (void)) (*constructor)) ();

	// Executes the kernel


	for (int i = 0; i < atExitIndex; i++)
		atExitDestructors[i].func(atExitDestructors[i].obj);

	for(unsigned long * destructor(& start_dtors); destructor < & end_dtors; ++destructor)
		((void (*) (void)) (* destructor)) ();
}

extern "C" void atexit(void (* f)(void *), void * obj)
{
	if (atExitIndex < ATEXIT_MAX_DESTRUCTORS)
	{
		atExitDestructors[atExitIndex].func = f;
		atExitDestructors[atExitIndex].obj  = obj;

		atExitIndex++;
	}
}

Code: Select all

crayon% uname -a
FreeBSD dev.localdomain 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Sat Nov 21 15:02:08 UTC 2009     [email protected]:/usr/obj/usr/src/sys/GENERIC  amd64
g++45 -v
Using built-in specs.
Target: x86_64-portbld-freebsd8.0
Configured with: ./../gcc-4.5-20090924/configure --disable-nls --with-system-zlib --with-libiconv-prefix=/usr/local --with-gmp=/usr/local --program-suffix=45 --libdir=/usr/local/lib/gcc45 --libexecdir=/usr/local/libexec/gcc45 --with-gxx-include-dir=/usr/local/lib/gcc45/include/c++/ --disable-libgcj --prefix=/usr/local --mandir=/usr/local/man --infodir=/usr/local/info/gcc45 --build=x86_64-portbld-freebsd8.0
Thread model: posix
gcc version 4.5.0 20090924 (experimental) (GCC)
crayon% cat main.cc
#include <iostream>

class foo {
public:
        foo(int val) : i(val) { }
        ~foo() {
            std::cout << "destroyed: i = " << i << std::endl;
        }

private:
        int i;
};

int
main(void)
{
        foo bar(10);
        return 0;
}
crayon% g++45 main.cc
crayon% ./a.out
destroyed: i = 10
objdump -h a.out | grep dtors
 19 .dtors        00000010  0000000000500dc0  0000000000500dc0  00000dc0  2**3

Code: Select all

There are 7 section headers, starting at offset 0x2034:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al

  [ 0]                   NULL            00000000 000000 000000 00      0   0  0

  [ 1] .text             PROGBITS        00100000 001000 001000 00  AX  0   0  4

  [ 2] .ctors            PROGBITS        00101000 002000 000004 00  WA  0   0  4

  [ 3] .bss              NOBITS          00101004 002004 000ffc 00  WA  0   0  4

  [ 4] .shstrtab         STRTAB          00000000 002004 00002d 00      0   0  1

  [ 5] .symtab           SYMTAB          00000000 00214c 000320 10      6  13  4

  [ 6] .strtab           STRTAB          00000000 00246c 000285 00      0   0  1

Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)