Bug #11790: [PATCH] ANSI alias rules fix

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[Zarko (Zarko Todorovski)]

line 70 in file regparse.h:

#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

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:

-#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));}

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

Does CAS work?

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

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset r52999.

---

regparse.h: ANSI alias rule fix

• regparse.h (SET_NTYPE): get rid of breaking strict aliasing.
  patch by Zarko Todorovski in [ruby-core:71953]. [Bug #11790]

[naruse (Yui NARUSE)]

• Related to Misc #11795: [PATCH] get rid of breaking strict alias for XL compiler added