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/* BFD library support routines for constructors
Copyright (C) 1990-1991 Free Software Foundation, Inc.
Hacked by Steve Chamberlain of Cygnus Support. With some help from
Judy Chamberlain too.
This file is part of BFD, the Binary File Descriptor library.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/*
SECTION
Constructors
DESCRIPTION
Classes in C++ have 'constructors' and 'destructors'. These
are functions which are called automatically by the language
whenever data of a class is created or destroyed. Class data
which is static data may also be have a type which requires
'construction', the contructor must be called before the data
can be referenced, so the contructor must be called before the
program begins.
The common solution to this problem is for the compiler to
call a magic function as the first statement <<main>>.
This magic function, (often called <<__main>>) runs around
calling the constructors for all the things needing it.
With COFF the compile has a bargain with the linker et al.
All constructors are given strange names, for example
<<__GLOBAL__$I$foo>> might be the label of a contructor for
the class @var{foo}. The solution on unfortunate systems
(most system V machines) is to perform a partial link on all
the .o files, do an <<nm>> on the result, run <<awk>> or some
such over the result looking for strange <<__GLOBAL__$>>
symbols, generate a C program from this, compile it and link
with the partially linked input. This process is usually
called <<collect>>.
Some versions of <<a.out>> use something called the
<<set_vector>> mechanism. The constructor symbols are output
from the compiler with a special stab code saying that they
are constructors, and the linker can deal with them directly.
BFD allows applications (ie the linker) to deal with
constructor information independently of their external
implimentation by providing a set of entry points for the
indiviual object back ends to call which maintains a database
of the contructor information. The application can
interrogate the database to find out what it wants. The
construction data essential for the linker to be able to
perform its job are:
o asymbol
The asymbol of the contructor entry point contains all the
information necessary to call the function.
o table id
The type of symbol, ie is it a contructor, a destructor or
something else someone dreamed up to make our lives difficult.
This module takes this information and then builds extra
sections attached to the bfds which own the entry points. It
creates these sections as if they were tables of pointers to
the entry points, and builds relocation entries to go with
them so that the tables can be relocated along with the data
they reference.
These sections are marked with a special bit
(<<SEC_CONSTRUCTOR>>) which the linker notices and do with
what it wants.
*/
#include <bfd.h>
#include <sysdep.h>
#include <libbfd.h>
/*
INTERNAL FUNCTION
bfd_constructor_entry
DESCRIPTION
This function is called with an a symbol describing the
function to be called, an string which descibes the xtor type,
eg something like "CTOR" or "DTOR" would be fine. And the bfd
which owns the function. Its duty is to create a section
called "CTOR" or "DTOR" or whatever if the bfd doesn't already
have one, and grow a relocation table for the entry points as
they accumulate.
SYNOPSIS
void bfd_constructor_entry(bfd *abfd,
asymbol **symbol_ptr_ptr,
CONST char*type);
*/
void DEFUN(bfd_constructor_entry,(abfd, symbol_ptr_ptr, type),
bfd *abfd AND
asymbol **symbol_ptr_ptr AND
CONST char *type)
{
/* Look up the section we're using to store the table in */
asection *rel_section = bfd_get_section_by_name (abfd, type);
if (rel_section == (asection *)NULL) {
rel_section = bfd_make_section (abfd, type);
rel_section->flags = SEC_CONSTRUCTOR;
rel_section->alignment_power = 2;
}
/* Create a relocation into the section which references the entry
point */
{
arelent_chain *reloc = (arelent_chain *)bfd_alloc(abfd,
sizeof(arelent_chain));
reloc->relent.section = (asection *)NULL;
reloc->relent.addend = 0;
reloc->relent.sym_ptr_ptr = symbol_ptr_ptr;
reloc->next = rel_section->constructor_chain;
rel_section->constructor_chain = reloc;
reloc->relent.address = rel_section->size;
/* ask the cpu which howto to use */
reloc->relent.howto =
bfd_reloc_type_lookup(abfd->arch_info,
BFD_RELOC_CTOR);
rel_section->size += sizeof(int *);
rel_section->reloc_count++;
}
}
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