shyouhei	2018-11-08 16:41:24 +0900 (Thu, 08 Nov 2018)

  New Revision: 65632

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=65632

  Log:
    hash.c: +(-1) is a wrong idea
    
    Before this changeset RHASH_ARRAY_SIZE_DEC() was expaneded to include
    an expression like `RHASH_ARRAY_SIZE+(-1)`.  RHASH_ARRAY_SIZE is by
    definition unsigned int.  -1 is signed, of course.  Adding a signed
    and an unsigned value requires the "usual arithmetic conversions" (cf:
    ISO/IEC 9899:1990 section 6.2.1.5).  -1 is converted to 0xFFFF by that.
    
    This patch prevents that conversion.

  Modified files:
    trunk/hash.c
Index: hash.c
===================================================================
--- hash.c	(revision 65631)
+++ hash.c	(revision 65632)
@@ -522,7 +522,11 @@ hash_array_set(VALUE hash, struct li_tab https://github.com/ruby/ruby/blob/trunk/hash.c#L522
 } while (0)
 
 #define RHASH_ARRAY_SIZE_INC(h) HASH_ARRAY_SIZE_ADD(h, 1)
-#define RHASH_ARRAY_SIZE_DEC(h) HASH_ARRAY_SIZE_ADD(h, -1)
+#define RHASH_ARRAY_SIZE_DEC(h) do  { \
+    HASH_ASSERT(RHASH_ARRAY_P(h)); \
+    RHASH_ARRAY_SIZE_SET((h), RHASH_ARRAY_SIZE(h) - 1); \
+    hash_verify(h); \
+} while (0)
 
 #define RHASH_CLEAR_BITS(h) do { \
     RBASIC(h)->flags &= ~RHASH_ARRAY_SIZE_MASK; \

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