@@ -64,38 +64,37 @@ uprv_free(void *mem);
6464U_CAPI void * U_EXPORT2
6565uprv_calloc (size_t num, size_t size) U_MALLOC_ATTR U_ALLOC_SIZE_ATTR2(1 ,2 );
6666
67- /* *
68- * This should align the memory properly on any machine.
69- * This is very useful for the safeClone functions.
70- */
71- typedef union {
72- long t1;
73- double t2;
74- void *t3;
75- } UAlignedMemory;
76-
7767/* *
7868 * Get the least significant bits of a pointer (a memory address).
7969 * For example, with a mask of 3, the macro gets the 2 least significant bits,
8070 * which will be 0 if the pointer is 32-bit (4-byte) aligned.
8171 *
82- * ptrdiff_t is the most appropriate integer type to cast to.
83- * size_t should work too, since on most (or all?) platforms it has the same
84- * width as ptrdiff_t.
72+ * uintptr_t is the most appropriate integer type to cast to.
8573*/
86- #define U_POINTER_MASK_LSB (ptr, mask ) ((( ptrdiff_t )( char *)( ptr) ) & (mask))
74+ #define U_POINTER_MASK_LSB (ptr, mask ) ((uintptr_t )( ptr) & (mask))
8775
8876/* *
89- * Get the amount of bytes that a pointer is off by from
90- * the previous UAlignedMemory-aligned pointer.
91- */
92- #define U_ALIGNMENT_OFFSET (ptr ) U_POINTER_MASK_LSB(ptr, sizeof (UAlignedMemory) - 1 )
93-
94- /* *
95- * Get the amount of bytes to add to a pointer
96- * in order to get the next UAlignedMemory-aligned address.
77+ * Create & return an instance of "type" in statically allocated storage.
78+ * e.g.
79+ * static std::mutex *myMutex = STATIC_NEW(std::mutex);
80+ * To destroy an object created in this way, invoke the destructor explicitly, e.g.
81+ * myMutex->~mutex();
82+ * DO NOT use delete.
83+ * DO NOT use with class UMutex, which has specific support for static instances.
84+ *
85+ * STATIC_NEW is intended for use when
86+ * - We want a static (or global) object.
87+ * - We don't want it to ever be destructed, or to explicitly control destruction,
88+ * to avoid use-after-destruction problems.
89+ * - We want to avoid an ordinary heap allocated object,
90+ * to avoid the possibility of memory allocation failures, and
91+ * to avoid memory leak reports, from valgrind, for example.
92+ * This is defined as a macro rather than a template function because each invocation
93+ * must define distinct static storage for the object being returned.
9794*/
98- #define U_ALIGNMENT_OFFSET_UP (ptr ) (sizeof (UAlignedMemory) - U_ALIGNMENT_OFFSET(ptr))
95+ #define STATIC_NEW (type ) [] (){\
96+ alignas (type) static char storage[sizeof (type)]; \
97+ return new (storage) type ()} ()
9998
10099/* *
101100 * Heap clean up function, called from u_cleanup()
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