Bug 15637 – Region allocator assert failure when expanding the last allocation

The following code crashes with an assert failure at std/experimental/allocator/building_blocks/region.d:235 on 64-bit Linux and 32-/64-bit Windows, using DMD version 2.070.0: import std.experimental.allocator; import std.experimental.allocator.building_blocks; void main(string[] args) { ubyte[1024] memory; auto alloc = Region!NullAllocator(memory); auto result = alloc.allocate(20); alloc.expand(result, 20); } The region allocator's expand function doesn't take into account any existing alignment padding when calculating the new allocation size, which pushes the _current pointer past the expected value. This could probably be fixed with something like: static if (growDownwards == No.growDownwards) bool expand(ref void[] b, size_t delta) { assert(owns(b) == Ternary.yes || b.ptr is null); assert(b.ptr + b.length <= _current || b.ptr is null); if (!b.ptr) { b = allocate(delta); return b.length == delta; } auto newLength = b.length + delta; if (_current < b.ptr + b.length + alignment) { immutable currentAllocSize = this.goodAllocSize(b.length); immutable requiredAllocSize = this.goodAllocSize(newLength); immutable allocDelta = requiredAllocSize - currentAllocSize; // This was the last allocation! Allocate some more and we're done. if (currentAllocSize == requiredAllocSize || allocate(allocDelta).length == allocDelta) { b = b.ptr[0 .. newLength]; assert(_current < b.ptr + b.length + alignment); return true; } } return false; }

Commits pushed to master at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/04cbf312a91c20ccddf029b5de8215edaf7a6f7e Fix Issue 15637 - Region allocator assert failure when expanding the last allocation https://github.com/dlang/phobos/commit/53e5cf67df078ad2157039d723ccba8d06f251ba Merge pull request #5852 from jercaianu/region Fix Issue 15637 - Region allocator assert failure when expanding the last allocation merged-on-behalf-of: Andrei Alexandrescu <[email protected]>

Commits pushed to stable at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/04cbf312a91c20ccddf029b5de8215edaf7a6f7e Fix Issue 15637 - Region allocator assert failure when expanding the last allocation https://github.com/dlang/phobos/commit/53e5cf67df078ad2157039d723ccba8d06f251ba Merge pull request #5852 from jercaianu/region