https://issues.dlang.org/show_bug.cgi?id=18848
Issue ID: 18848
Summary: std.allocator: Regions are non-copyable, yet are
passed around in examples
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P1
Component: phobos
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Here is an example from
std.experimental.allocator.building_blocks.allocator_list.AllocatorList:
// Ouroboros allocator list based upon 4MB regions, fetched directly from
// mmap. All memory is released upon destruction.
alias A1 = AllocatorList!((n) => Region!MmapAllocator(max(n, 1024 * 4096)),
NullAllocator);
The example features a lambda returning a Region.
However, Regions cannot be copied, as they have a destructor which deallocates
everything. A comment in the implementation says:
/*
TODO: The postblit of $(D BasicRegion) should be disabled because such
objects
should not be copied around naively.
*/
(That's the only occurrence of BasicRegion in Phobos, so I assume that's just
an old name for Region.)
Though NRVO may make the verbatim example code behave correctly, it is fragile,
and small code modifications e.g. to work around issue 18848 can cause
difficult-to-debug problems (due to dangling pointers in other Region
instances).
--
