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Message-Id: <200802042314.18738.rusty@rustcorp.com.au> Date: Mon, 4 Feb 2008 23:14:18 +1100 From: Rusty Russell <rusty@...tcorp.com.au> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: linux-kernel@...r.kernel.org Subject: [PATCH 1/5] cast_if_type: allow macros functions which take more than one type. 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@...tcorp.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)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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