Improve comment about size of ARENA_BITS.

nascheme · nascheme · commit 257ba989bf79 · 2019-06-30T13:44:41.000-07:00
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
@@ -2984,7 +2984,7 @@ arena_map_is_marked(block *p)
         return 0;
     }
     int i3 = MAP3_INDEX(p);
-    /* in order to fit tail into 32-bits, ARENA_BITS must be <= 32 */
+    /* ARENA_BITS must be < 32 so that the tail is a non-negative int32_t. */
     int32_t hi = n->arenas[i3].tail_hi;
     int32_t lo = n->arenas[i3].tail_lo;
     int32_t tail = (int32_t)(AS_UINT(p) & ARENA_MASK);

Original file line number	Diff line number	Diff line change
`@@ -2984,7 +2984,7 @@ arena_map_is_marked(block *p)`
`2984`	`2984`	`return 0;`
`2985`	`2985`	`}`
`2986`	`2986`	`int i3 = MAP3_INDEX(p);`
`2987`		`- /* in order to fit tail into 32-bits, ARENA_BITS must be <= 32 */`
	`2987`	`+ /* ARENA_BITS must be < 32 so that the tail is a non-negative int32_t. */`
`2988`	`2988`	`int32_t hi = n->arenas[i3].tail_hi;`
`2989`	`2989`	`int32_t lo = n->arenas[i3].tail_lo;`
`2990`	`2990`	`int32_t tail = (int32_t)(AS_UINT(p) & ARENA_MASK);`