Bug 18914 – std.experimental.allocator randomly fails on Darwin_64_64

It's a blocker because it randomly causes the autotester to fail, such as here: https://auto-tester.puremagic.com/show-run.ghtml?projectid=1&runid=3185054&isPull=true The failing message: 0.066s PASS release64 std.experimental.allocator.building_blocks.allocator_list testAllocator failed for BitmappedBlock!(64LU, 8u, NullAllocator, cast(Flag)true) ****** FAIL release64 std.experimental.allocator.building_blocks.bucketizer core.exception.AssertError@std/experimental/allocator/building_blocks/bitmapped_block.d(112): Data must be aligned properly ---------------- ??:? _d_assert_msg [0x71d728e] ??:? pure nothrow ref @nogc std.experimental.allocator.building_blocks.bitmapped_block.BitmappedBlock!(64uL, 8u, std.experimental.allocator.building_blocks.null_allocator.NullAllocator, 1).BitmappedBlock std.experimental.allocator.building_blocks.bitmapped_block.BitmappedBlock!(64uL, 8u, std.experimental.allocator.building_blocks.null_allocator.NullAllocator, 1).BitmappedBlock.__mixin2.__ctor(ubyte[]) [0x6d880b7] ??:? pure nothrow @nogc std.experimental.allocator.building_blocks.bitmapped_block.BitmappedBlock!(64uL, 8u, std.experimental.allocator.building_blocks.null_allocator.NullAllocator, 1).BitmappedBlock std.experimental.allocator.building_blocks.bitmapped_block.BitmappedBlock!(64uL, 8u, std.experimental.allocator.gc_allocator.GCAllocator, 1).BitmappedBlock.__unittest_L1344_C17_1().__lambda2() [0x6d8a33f] ??:? void std.experimental.allocator.common.testAllocator!(std.experimental.allocator.building_blocks.bitmapped_block.BitmappedBlock!(64uL, 8u, std.experimental.allocator.gc_allocator.GCAllocator, 1).BitmappedBlock.__unittest_L1344_C17_1().__lambda2()).testAllocator() [0x6d89af6] ??:? void std.experimental.allocator.building_blocks.bitmapped_block.BitmappedBlock!(64uL, 8u, std.experimental.allocator.gc_allocator.GCAllocator, 1).BitmappedBlock.__unittest_L1344_C17_1() [0x6d86284] ??:? void std.experimental.allocator.building_blocks.bucketizer.__modtest() [0x6d81c38] ??:? void test_runner.doTest(object.ModuleInfo*, ref core.runtime.UnitTestResult) [0x5dde6d4] ??:? core.runtime.UnitTestResult test_runner.testModules() [0x5dde60b] ??:? core.runtime.UnitTestResult test_runner.tester() [0x5dde4df] ??:? runModuleUnitTests [0x71d7e0a] ??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runAll() [0x71ec96c] ??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate()) [0x71ec8f7] ??:? _d_run_main [0x71ec865] ??:? main [0x5dde383] ??:? start [0x5dde353] ??:? 0x0 [0x1]

*** This issue has been marked as a duplicate of issue 18140 ***