in malloc, compute memory sizes in size_t

Some size computations were using the wrong data type, in particular
getting a signed 32-bit type where unsigned 64-bit is required on
LP64 systems.  That resulted in truncation and in sign extension during
later conversion to the correct type, either way producing bogus sizes.
Fix by casting everything to size_t suitably early.  Fixes [perl #119829].

malloc.c

@@ -466,12 +466,12 @@ static const u_short buck_size[MAX_BUCKET_BY_TABLE + 1] =
   };
 #  define BUCKET_SIZE_NO_SURPLUS(i) ((i) % 2 ? buck_size[i] : (1 << ((i) >> BUCKET_POW2_SHIFT)))
 #  define BUCKET_SIZE_REAL(i) ((i) <= MAX_BUCKET_BY_TABLE		\
-			       ? buck_size[i] 				\
-			       : ((1 << ((i) >> BUCKET_POW2_SHIFT))	\
+			       ? ((size_t)buck_size[i])			\
+			       : ((((size_t)1) << ((i) >> BUCKET_POW2_SHIFT)) \
 				  - MEM_OVERHEAD(i)			\
 				  + POW2_OPTIMIZE_SURPLUS(i)))
 #else
-#  define BUCKET_SIZE_NO_SURPLUS(i) (1 << ((i) >> BUCKET_POW2_SHIFT))
+#  define BUCKET_SIZE_NO_SURPLUS(i) (((size_t)1) << ((i) >> BUCKET_POW2_SHIFT))
 #  define BUCKET_SIZE(i) (BUCKET_SIZE_NO_SURPLUS(i) + POW2_OPTIMIZE_SURPLUS(i))
 #  define BUCKET_SIZE_REAL(i) (BUCKET_SIZE(i) - MEM_OVERHEAD(i))
 #endif 
@@ -686,7 +686,7 @@ static const u_short blk_shift[LOG_OF_MIN_ARENA * BUCKETS_PER_POW2] =
 
 #ifdef PACK_MALLOC
 #  define MEM_OVERHEAD(bucket) \
-  (bucket <= MAX_PACKED ? 0 : M_OVERHEAD)
+  (bucket <= MAX_PACKED ? ((size_t)0) : M_OVERHEAD)
 #  ifdef SMALL_BUCKET_VIA_TABLE
 #    define START_SHIFTS_BUCKET ((MAX_PACKED_POW2 + 1) * BUCKETS_PER_POW2)
 #    define START_SHIFT MAX_PACKED_POW2
@@ -752,11 +752,11 @@ static const char bucket_of[] =
 #  define POW2_OPTIMIZE_ADJUST(nbytes)				\
    ((nbytes >= FIRST_BIG_BOUND) ? nbytes -= PERL_PAGESIZE : 0)
 #  define POW2_OPTIMIZE_SURPLUS(bucket)				\
-   ((bucket >= FIRST_BIG_POW2 * BUCKETS_PER_POW2) ? PERL_PAGESIZE : 0)
+   ((size_t)((bucket >= FIRST_BIG_POW2 * BUCKETS_PER_POW2) ? PERL_PAGESIZE : 0))
 
 #else  /* !TWO_POT_OPTIMIZE */
 #  define POW2_OPTIMIZE_ADJUST(nbytes)
-#  define POW2_OPTIMIZE_SURPLUS(bucket) 0
+#  define POW2_OPTIMIZE_SURPLUS(bucket) ((size_t)0)
 #endif /* !TWO_POT_OPTIMIZE */
 
 #define BARK_64K_LIMIT(what,nbytes,size)

pod/perldelta.pod

@@ -378,6 +378,11 @@ files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
 
 XXX
 
+=item *
+
+Perl's own C<malloc> no longer gets confused by attempts to allocate
+more than 4 GiB on a 64-bit platform.  [perl #119829]
+
 =back
 
 =head1 Known Problems