freebsd-nq/lib/csu/i386/c++rt0.c
John Polstra d5489b0d8f Check the count in the first word of __CTOR_LIST__ before executing
the loop that invokes the static constructors.  That makes it safe
to link c++rt0.o into any shared library, even one that does not
have any static constructors.  Formerly, doing that would cause a
bus error.  If the library has no static constructors, __CTOR_LIST__
comes out as a simple 4-byte COMMON region, and it does not have
the usual NULL word that terminates the list of constructors.  This
caused the old code to "call" a garbage address via the non-existent
entry __CTOR_LIST__[1].

The analogous code that invokes the static destructors was already safe.

This change is fully backward-compatible.

Reviewed by:	dfr@render.com (Doug Rabson)
1996-01-15 17:53:25 +00:00

95 lines
2.8 KiB
C

/*
* Copyright (c) 1993 Paul Kranenburg
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Paul Kranenburg.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $Id: c++rt0.c,v 1.3 1995/06/27 09:53:24 dfr Exp $
*/
/*
* Run-time module for GNU C++ compiled shared libraries.
*
* The linker constructs the following arrays of pointers to global
* constructors and destructors. The first element contains the
* number of pointers in each.
* The tables are also null-terminated.
*/
void (*__CTOR_LIST__[0])(void);
void (*__DTOR_LIST__[0])(void);
static void
__dtors(void)
{
unsigned long i = (unsigned long) __DTOR_LIST__[0];
void (**p)(void) = __DTOR_LIST__ + i;
while (i--)
(**p--)();
}
static void
__ctors(void)
{
/*
* If the shared library doesn't have any static constructors in it,
* then __CTOR_LIST__ will come out as a simple COMMON region of
* 4 bytes. That is why we have to check the count in the first
* word.
*/
if ((unsigned long) __CTOR_LIST__[0] > 0) {
void (**p)(void) = __CTOR_LIST__ + 1;
while (*p)
(**p++)();
}
}
extern void __init() asm(".init");
extern void __fini() asm(".fini");
void
__init(void)
{
static int initialized = 0;
/*
* Call global constructors.
* Arrange to call global destructors at exit.
*/
if (!initialized) {
initialized = 1;
__ctors();
}
}
void
__fini(void)
{
__dtors();
}