[ltt-dev] [PATCH RFC] Force build failure on unknown architectures

[Paul E. McKenney]

Create urcu/arch_unknown.h and urcu/uatomic_arch_unknown.h, which
contain only #error statements and explanatory comments.  This forces
build failures on unrecognized architectures in preference to trying
to guess at what operations might be safe on such architectures.

One other semi-feasible alternative is to use hashed arrays of locks
that are acquired with signals disabled.  However, this seems a bit
too ornate, especially for architectures for which the gcc __sync_
primitives work correctly.

Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
---

 arch_unknown.h         |   32 ++++++++++++++++++++++++++++++++
 uatomic_arch_unknown.h |   29 +++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/urcu/arch_unknown.h b/urcu/arch_unknown.h
new file mode 100644
index 0000000..91395ff
--- /dev/null
+++ b/urcu/arch_unknown.h
@@ -0,0 +1,32 @@
+#ifndef _URCU_ARCH_UNKNOWN_H
+#define _URCU_ARCH_UNKNOWN_H
+
+/*
+ * arch_unknown.h: #error to prevent build on unknown architectures.
+ *
+ * Copyright (c) 2010 Paul E. McKenney, IBM Corporation.
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers at polymtl.ca>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/*
+ * See configure.ac for the list of recognized architectures.
+ * Alternatively, "ls arch_*.h" in this directory, ignoring
+ * this "arch_unknown.h" file.
+ */
+#error "Cannot build: unrecognized architecture detected."
+
+#endif /* _URCU_ARCH_UNKNOWN_H */
diff --git a/urcu/uatomic_arch_unknown.h b/urcu/uatomic_arch_unknown.h
new file mode 100644
index 0000000..d104fe1
--- /dev/null
+++ b/urcu/uatomic_arch_unknown.h
@@ -0,0 +1,29 @@
+#ifndef _URCU_ARCH_UATOMIC_UNKNOWN_H
+#define _URCU_ARCH_UATOMIC_UNKNOWN_H
+
+/* 
+ * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
+ * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
+ * Copyright (c) 1999-2004 Hewlett-Packard Development Company, L.P.
+ * Copyright (c) 2009      Mathieu Desnoyers
+ * Copyright (c) 2010      Paul E. McKenney, IBM Corporation
+ *			   (Adapted from uatomic_arch_ppc.h)
+ *
+ * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+ * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+ *
+ * Permission is hereby granted to use or copy this program
+ * for any purpose,  provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is granted,
+ * provided the above notices are retained, and a notice that the code was
+ * modified is included with the above copyright notice.
+ */
+
+/*
+ * See configure.ac for the list of recognized architectures.
+ * Alternatively, "ls uatomic_arch_*.h" in this directory, ignoring
+ * this "uatomic_arch_unknown.h" file.
+ */
+#error "Cannot build: unrecognized architecture detected."
+
+#endif /* _URCU_ARCH_UATOMIC_UNKNOWN_H */