From: nobu@...
Date: 2015-12-08T23:24:59+00:00
Subject: [ruby-core:71959] [Ruby trunk - Bug #11790] [PATCH] ANSI alias	rules fix

Issue #11790 has been updated by Nobuyoshi Nakada.

Description updated

Does CAS work?

~~~c
  /* THREAD_ATOMIC_START; */
  {
    FreeNode *n = FreeNodeList, *n0;
    while (IS_NOT_NULL(n) && (n0 = ATOMIC_PTR_CAS(FreeNodeList, n, n->next)) != n)
      n = n0;
    return (Node* )FreeNodeList;
  }
  /* THREAD_ATOMIC_END; */
~~~

----------------------------------------
Bug #11790: [PATCH] ANSI alias rules fix 
https://bugs.ruby-lang.org/issues/11790#change-55369

* Author: Zarko  Todorovski
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
line 70 in file regparse.h:

~~~c
#define SET_NTYPE(node, ntype)   (node)->u.base.type = (ntype)
~~~

needs to be changed to conform with ANSI alias rules


Line 70 as it is can lead to errors in compiling in regparse.c

~~~c
line 1143: node = (Node* )FreeNodeList;
line 1144: FreeNodeList = FreeNodeList->next;
line 1581: (node)->u.base.type = (0);
~~~

where during compiling line 1581 can be moved ahead of line 1144 since under ANSI aliasing rules, the compiler determines that the statement of "(node)->u.base.type = (0);" does not affect the value of FreeNodeList. 

Proposed change in patch is in file regparse.h:

~~~diff
-#define SET_NTYPE(node, ntype)   (node)->u.base.type = (ntype)
+#define SET_NTYPE(node, ntype)  {int value = ntype; memcpy(&((node)->u.base.type), &value, sizeof((node)->u.base.type));}
~~~

---Files--------------------------------
alias_ansi_rule.patch (717 Bytes)


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