From f3112eb32a9ab6759bb4b9834740fd84ca57dacb Mon Sep 17 00:00:00 2001
From: John Polstra <jdp@FreeBSD.org>
Date: Wed, 9 Apr 1997 19:14:31 +0000
Subject: [PATCH] Declare the constructor/destructor linker sets as extern
 rather than common.  Add one do-nothing element to each set.  This ensures
 that the linker realizes that they are linker sets rather than simple
 commons, and makes it possible to link c++rt0.o into every shared library
 regardless of whether it is a C++ library or not.  Without this change, the
 constructors and destructors in the main program could be executed multiple
 times.

This change is going to make it possible to get rid of the
CPLUSPLUSLIB makefile variable once and for all.  It is a piece of
the solution to PR gnu/3505 (gcc -shared).  Finally, it fixes a
heretofore unreported bug:  If CPLUSPLUSLIB was set in a makefile
for a C++ shared library that had no static constructors or
destructors in it, then the main program's constructors and
destructors would be executed multiple times.
---
 lib/csu/i386/c++rt0.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/lib/csu/i386/c++rt0.c b/lib/csu/i386/c++rt0.c
index 94fa5c59b2b..413524f03ec 100644
--- a/lib/csu/i386/c++rt0.c
+++ b/lib/csu/i386/c++rt0.c
@@ -27,7 +27,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- *	$Id$
+ *	$Id: c++rt0.c,v 1.7 1997/02/22 14:57:42 peter Exp $
  */
 
 /*
@@ -38,8 +38,8 @@
  * number of pointers in each.
  * The tables are also null-terminated.
  */
-void (*__CTOR_LIST__[2])(void);
-void (*__DTOR_LIST__[2])(void);
+extern void (*__CTOR_LIST__[])(void);
+extern void (*__DTOR_LIST__[])(void);
 
 static void
 __dtors(void)
@@ -84,3 +84,24 @@ __fini(void)
 {
 	__dtors();
 }
+
+/*
+ * Make sure there is at least one constructor and one destructor in the
+ * shared library.  Otherwise, the linker does not realize that the
+ * constructor and destructor lists are linker sets.  It treats them as
+ * commons and resolves them to the lists from the main program.  That
+ * causes multiple invocations of the main program's static constructors
+ * and destructors, which is very bad.
+ */
+
+static void
+do_nothing(void)
+{
+}
+
+/* Linker magic to add an element to a constructor or destructor list. */
+#define TEXT_SET(set, sym) \
+	asm(".stabs \"_" #set "\", 23, 0, 0, _" #sym)
+
+TEXT_SET(__CTOR_LIST__, do_nothing);
+TEXT_SET(__DTOR_LIST__, do_nothing);