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From: Rusty Russell <rusty@rustcorp.com.au>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH 1/5] cast_if_type: allow macros functions which take more than one type.
Date: Mon, 4 Feb 2008 23:14:18 +1100	[thread overview]
Message-ID: <200802042314.18738.rusty@rustcorp.com.au> (raw)
In-Reply-To: <200802042311.18762.rusty@rustcorp.com.au>

To create functions which can take two types, but still warn on any
other types, we need a way of casting one type and no others.

To make things more complex, it should correctly handle function args,
NULL, and be usable in initializers.  __builtin_choose_expr was introduced
in gcc 3.1 (we need >= 3.2 anyway).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 include/linux/compiler-gcc.h   |   17 +++++++++++++++++
 include/linux/compiler-intel.h |    2 ++
 2 files changed, 19 insertions(+)

diff -r e6626cc7bdc2 include/linux/compiler-gcc.h
--- a/include/linux/compiler-gcc.h	Sun Jan 20 18:51:51 2008 +1100
+++ b/include/linux/compiler-gcc.h	Sun Jan 20 18:57:14 2008 +1100
@@ -53,3 +53,20 @@
 #define  noinline			__attribute__((noinline))
 #define __attribute_const__		__attribute__((__const__))
 #define __maybe_unused			__attribute__((unused))
+
+/**
+ * cast_if_type - allow an alternate type
+ * @expr: the expression to optionally cast
+ * @oktype: the type to allow.
+ * @desttype: the type to cast to.
+ *
+ * This is used to accept a particular alternate type for an expression:
+ * because any other types will not be cast, they will cause a warning as
+ * normal.
+ *
+ * Note that the unnecessary trinary forces functions to devolve into
+ * function pointers as users expect. */
+#define cast_if_type(expr, oktype, desttype)				\
+  __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):NULL), \
+						     oktype),		\
+			(desttype)(expr), (expr))
diff -r e6626cc7bdc2 include/linux/compiler-intel.h
--- a/include/linux/compiler-intel.h	Sun Jan 20 18:51:51 2008 +1100
+++ b/include/linux/compiler-intel.h	Sun Jan 20 18:57:14 2008 +1100
@@ -29,3 +29,5 @@
 #endif
 
 #define uninitialized_var(x) x
+
+#define cast_if_type(expr, oktype, desttype) ((desttype)(expr))

  reply	other threads:[~2008-02-04 12:14 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-04 12:11 [PATCH 0/5] typesafe callbacks Rusty Russell
2008-02-04 12:14 ` Rusty Russell [this message]
2008-02-04 12:16   ` [PATCH 2/5] typesafe: Convert stop_machine Rusty Russell
2008-02-04 12:17     ` [PATCH 3/5] typesafe: kthread_create and kthread_run Rusty Russell
2008-02-04 12:18       ` [PATCH 4/5] typesafe: request_irq and devm_request_irq Rusty Russell
2008-02-04 12:19         ` [PATCH 5/5] typesafe: TIMER_INITIALIZER and setup_timer Rusty Russell
2008-02-04 14:57           ` Al Viro
2008-02-05  3:41             ` Rusty Russell
2008-03-05  2:55               ` Rusty Russell
2008-03-06 10:40                 ` Al Viro
2008-03-10  1:07                   ` Rusty Russell
2008-03-10  2:03                     ` Al Viro
2008-03-10  3:42                       ` Rusty Russell

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