[Python-checkins] CVS: python/dist/src/Include objimpl.h,2.42,2.43

[Tim Peters]

Update of /cvsroot/python/python/dist/src/Include
In directory usw-pr-cvs1:/tmp/cvs-serv23954/python/Include

Modified Files:
	objimpl.h 
Log Message:
SF bug [#467145] Python 2.2a4 build problem on HPUX 11.0.
The platform requires 8-byte alignment for doubles, but the GC header
was 12 bytes and that threw off the natural alignment of the double
members of a subtype of complex.  The fix puts the GC header into a
union with a double as the other member, to force no-looser-than
double alignment of GC headers.  On boxes that require 8-byte alignment
for doubles, this may add pad bytes to the GC header accordingly; ditto
for platforms that *prefer* 8-byte alignment for doubles.  On platforms
that don't care, it shouldn't change the memory layout (because the
size of the old GC header is certainly greater than the size of a double
on all platforms, so unioning with a double shouldn't change size or
alignment on such boxes).


Index: objimpl.h
===================================================================
RCS file: /cvsroot/python/python/dist/src/Include/objimpl.h,v
retrieving revision 2.42
retrieving revision 2.43
diff -C2 -d -r2.42 -r2.43
*** objimpl.h	2001/10/07 03:54:51	2.42
--- objimpl.h	2001/10/11 18:31:31	2.43
***************
*** 267,274 ****
  
  /* GC information is stored BEFORE the object structure */
! typedef struct _gc_head {
! 	struct _gc_head *gc_next; /* not NULL if object is tracked */
! 	struct _gc_head *gc_prev;
! 	int gc_refs;
  } PyGC_Head;
  
--- 267,277 ----
  
  /* GC information is stored BEFORE the object structure */
! typedef union _gc_head {
! 	struct {
! 		union _gc_head *gc_next; /* not NULL if object is tracked */
! 		union _gc_head *gc_prev;
! 		int gc_refs;
! 	} gc;
! 	double dummy;  /* force worst-case alignment */
  } PyGC_Head;
  
***************
*** 279,288 ****
  #define _PyObject_GC_TRACK(o) do { \
  	PyGC_Head *g = (PyGC_Head *)(o)-1; \
! 	if (g->gc_next != NULL) \
  		Py_FatalError("GC object already in linked list"); \
! 	g->gc_next = &_PyGC_generation0; \
! 	g->gc_prev = _PyGC_generation0.gc_prev; \
! 	g->gc_prev->gc_next = g; \
! 	_PyGC_generation0.gc_prev = g; \
      } while (0);
  
--- 282,291 ----
  #define _PyObject_GC_TRACK(o) do { \
  	PyGC_Head *g = (PyGC_Head *)(o)-1; \
! 	if (g->gc.gc_next != NULL) \
  		Py_FatalError("GC object already in linked list"); \
! 	g->gc.gc_next = &_PyGC_generation0; \
! 	g->gc.gc_prev = _PyGC_generation0.gc.gc_prev; \
! 	g->gc.gc_prev->gc.gc_next = g; \
! 	_PyGC_generation0.gc.gc_prev = g; \
      } while (0);
  
***************
*** 290,296 ****
  #define _PyObject_GC_UNTRACK(o) do { \
  	PyGC_Head *g = (PyGC_Head *)(o)-1; \
! 	g->gc_prev->gc_next = g->gc_next; \
! 	g->gc_next->gc_prev = g->gc_prev; \
! 	g->gc_next = NULL; \
      } while (0);
  
--- 293,299 ----
  #define _PyObject_GC_UNTRACK(o) do { \
  	PyGC_Head *g = (PyGC_Head *)(o)-1; \
! 	g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \
! 	g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \
! 	g->gc.gc_next = NULL; \
      } while (0);