ruby-dev

Issue #5469 has been reported by Naohisa Goto.

----------------------------------------
Bug #5469: Bus Error when accessing NAN and INFINITY
http://redmine.ruby-lang.org/issues/5469

Author: Naohisa Goto
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: -


現在、INFINITYやNANが処理系で定義されていない場合、numeric.c 内の以下の変数を使います。
 const unsigned char rb_infinity[] = "\x00\x00\x80\x7f";
 const unsigned char rb_nan[] = "\x00\x00\xc0\x7f";
(上記はlittle endianの場合のみピックアップ)
しかし、この記述はワード境界のアラインメントを一切考慮していないため、
処理系とCPUアーキテクチャの組み合わせによっては、Bus Error が出ます。
具体的には、Sparc Solaris 10 上の Fujitsu C Compiler 5.6 で作成すると Bus Error が出ました。

以下のパッチのように共用体にすると大丈夫でした。
ただしバイナリ互換性は保たれなくなる気がします。

同じ記述は 1.9.3 にもありますが、メジャーな環境では起きていないようなので、バックポートする必要はないと思います。

===================================================================
--- include/ruby/missing.h	(revision 33498)
+++ include/ruby/missing.h	(working copy)
@@ -124,20 +124,27 @@
 RUBY_EXTERN double cbrt(double);
 #endif
 
+#if !defined(INFINITY) || !defined(NAN)
+union bytestream4_or_float {
+  unsigned char stream[4]; 
+  float float_value;
+};
+#endif
+
 #ifdef INFINITY
 # define HAVE_INFINITY
 #else
 /** @internal */
-RUBY_EXTERN const unsigned char rb_infinity[];
-# define INFINITY (*(float *)rb_infinity)
+RUBY_EXTERN const union bytestream4_or_float rb_infinity;
+# define INFINITY (rb_infinity.float_value)
 #endif
 
 #ifdef NAN
 # define HAVE_NAN
 #else
 /** @internal */
-RUBY_EXTERN const unsigned char rb_nan[];
-# define NAN (*(float *)rb_nan)
+RUBY_EXTERN const union bytestream4_or_float rb_nan;
+# define NAN (rb_nan.float_value)
 #endif
 
 #ifndef isinf
Index: numeric.c
===================================================================
--- numeric.c	(revision 33498)
+++ numeric.c	(working copy)
@@ -66,16 +66,16 @@
 
 #ifdef HAVE_INFINITY
 #elif !defined(WORDS_BIGENDIAN) /* BYTE_ORDER == LITTLE_ENDIAN */
-const unsigned char rb_infinity[] = "\x00\x00\x80\x7f";
+const union bytestream4_or_float rb_infinity = { 0x00, 0x00, 0x80, 0x7f };
 #else
-const unsigned char rb_infinity[] = "\x7f\x80\x00\x00";
+const union bytestream4_or_float rb_infinity = { 0x7f, 0x80, 0x00, 0x00 };
 #endif
 
 #ifdef HAVE_NAN
 #elif !defined(WORDS_BIGENDIAN) /* BYTE_ORDER == LITTLE_ENDIAN */
-const unsigned char rb_nan[] = "\x00\x00\xc0\x7f";
+const union bytestream4_or_float rb_nan = { 0x00, 0x00, 0xc0, 0x7f };
 #else
-const unsigned char rb_nan[] = "\x7f\xc0\x00\x00";
+const union bytestream4_or_float rb_nan = { 0x7f, 0xc0, 0x00, 0x00 };
 #endif
 
 #ifndef HAVE_ROUND




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