| ... | ... | @@ -261,7 +261,9 @@ const Node = struct { |
| 261 | 261 | return @as([*]u8, @ptrCast(node))[0..size.toInt()]; |
| 262 | 262 | } |
| 263 | 263 | |
| 264 | | fn endResize(node: *Node, size: usize) void { |
| 264 | fn endResize(node: *Node, size: usize, prev_size: usize) void { |
| 265 | assert(size >= prev_size); // nodes must not shrink |
| 266 | assert(@atomicLoad(Size, &node.size, .unordered).toInt() == prev_size); |
| 265 | 267 | return @atomicStore(Size, &node.size, .fromInt(size), .release); // syncs with acquire in `beginResize` |
| 266 | 268 | } |
| 267 | 269 | |
| ... | ... | @@ -302,6 +304,8 @@ fn stealFreeList(arena: *ArenaAllocator) ?*Node { |
| 302 | 304 | |
| 303 | 305 | fn pushFreeList(arena: *ArenaAllocator, first: *Node, last: *Node) void { |
| 304 | 306 | assert(first != last.next); |
| 307 | assert(first != first.next); |
| 308 | assert(last != last.next); |
| 305 | 309 | while (@cmpxchgWeak( |
| 306 | 310 | ?*Node, |
| 307 | 311 | &arena.state.free_list, |
| ... | ... | @@ -315,8 +319,10 @@ fn pushFreeList(arena: *ArenaAllocator, first: *Node, last: *Node) void { |
| 315 | 319 | } |
| 316 | 320 | |
| 317 | 321 | fn alignedIndex(buf_ptr: [*]u8, end_index: usize, alignment: Alignment) usize { |
| 318 | | return end_index + |
| 319 | | mem.alignPointerOffset(buf_ptr + end_index, alignment.toByteUnits()).?; |
| 322 | // Wrapping arithmetic to avoid overflows since `end_index` isn't bounded by |
| 323 | // `size`. This is always ok since the max alignment in byte units is also |
| 324 | // the max value of `usize` so wrapped values are correctly aligned anyway. |
| 325 | return alignment.forward(@intFromPtr(buf_ptr) +% end_index) -% @intFromPtr(buf_ptr); |
| 320 | 326 | } |
| 321 | 327 | |
| 322 | 328 | fn alloc(ctx: *anyopaque, n: usize, alignment: Alignment, ret_addr: usize) ?[*]u8 { |
| ... | ... | @@ -362,7 +368,7 @@ fn alloc(ctx: *anyopaque, n: usize, alignment: Alignment, ret_addr: usize) ?[*]u |
| 362 | 368 | const node = first_node orelse break :resize; |
| 363 | 369 | const allocated_slice = node.beginResize() orelse break :resize; |
| 364 | 370 | var size = allocated_slice.len; |
| 365 | | defer node.endResize(size); |
| 371 | defer node.endResize(size, allocated_slice.len); |
| 366 | 372 | |
| 367 | 373 | const buf = allocated_slice[@sizeOf(Node)..]; |
| 368 | 374 | const end_index = @atomicLoad(usize, &node.end_index, .monotonic); |
| ... | ... | @@ -404,92 +410,81 @@ fn alloc(ctx: *anyopaque, n: usize, alignment: Alignment, ret_addr: usize) ?[*]u |
| 404 | 410 | // Also this avoids the ABA problem; stealing the list with an atomic |
| 405 | 411 | // swap doesn't introduce any potentially stale `next` pointers. |
| 406 | 412 | |
| 407 | | const free_list = arena.stealFreeList(); |
| 408 | | var first_free: ?*Node = free_list; |
| 409 | | var last_free: ?*Node = free_list; |
| 410 | | defer { |
| 411 | | // Push remaining stolen free list back onto `arena.state.free_list`. |
| 412 | | if (first_free) |first| { |
| 413 | | const last = last_free.?; |
| 414 | | assert(last.next == null); // optimize for no new nodes added during steal |
| 415 | | arena.pushFreeList(first, last); |
| 416 | | } |
| 417 | | } |
| 413 | const free_list = arena.stealFreeList() orelse break :from_free_list; |
| 418 | 414 | |
| 419 | | const candidate: ?*Node, const prev: ?*Node = candidate: { |
| 415 | const first_free: *Node, const last_free: *Node, const node: *Node, const prev: ?*Node = find: { |
| 420 | 416 | var best_fit_prev: ?*Node = null; |
| 421 | 417 | var best_fit: ?*Node = null; |
| 422 | 418 | var best_fit_diff: usize = std.math.maxInt(usize); |
| 423 | 419 | |
| 424 | 420 | var it_prev: ?*Node = null; |
| 425 | | var it = free_list; |
| 421 | var it: ?*Node = free_list; |
| 426 | 422 | while (it) |node| : ({ |
| 427 | | it_prev = it; |
| 423 | it_prev = node; |
| 428 | 424 | it = node.next; |
| 429 | 425 | }) { |
| 430 | | last_free = node; |
| 431 | 426 | assert(!node.size.resizing); |
| 432 | 427 | const buf = node.allocatedSliceUnsafe()[@sizeOf(Node)..]; |
| 433 | 428 | const aligned_index = alignedIndex(buf.ptr, 0, alignment); |
| 434 | 429 | |
| 435 | | if (aligned_index + n <= buf.len) { |
| 436 | | break :candidate .{ node, it_prev }; |
| 437 | | } |
| 438 | | |
| 439 | | const diff = aligned_index + n - buf.len; |
| 440 | | if (diff <= best_fit_diff) { |
| 430 | const diff = aligned_index + n -| buf.len; |
| 431 | if (diff < best_fit_diff) { |
| 441 | 432 | best_fit_prev = it_prev; |
| 442 | 433 | best_fit = node; |
| 443 | 434 | best_fit_diff = diff; |
| 444 | 435 | } |
| 445 | | } else { |
| 446 | | // Ideally we want to use all nodes in `free_list` eventually, |
| 447 | | // so even if none fit we'll try to resize the one that was the |
| 448 | | // closest to being large enough. |
| 449 | | if (best_fit) |node| { |
| 450 | | const allocated_slice = node.allocatedSliceUnsafe(); |
| 451 | | const buf = allocated_slice[@sizeOf(Node)..]; |
| 452 | | const aligned_index = alignedIndex(buf.ptr, 0, alignment); |
| 453 | | const new_size = mem.alignForward(usize, @sizeOf(Node) + aligned_index + n, 2); |
| 454 | | |
| 455 | | if (arena.child_allocator.rawResize(allocated_slice, .of(Node), new_size, @returnAddress())) { |
| 456 | | node.size = .fromInt(new_size); |
| 457 | | break :candidate .{ node, best_fit_prev }; |
| 458 | | } |
| 459 | | } |
| 460 | | break :from_free_list; |
| 461 | 436 | } |
| 437 | |
| 438 | break :find .{ free_list, it_prev.?, best_fit.?, best_fit_prev }; |
| 439 | }; |
| 440 | |
| 441 | const aligned_index, const need_resize = aligned_index: { |
| 442 | const buf = node.allocatedSliceUnsafe()[@sizeOf(Node)..]; |
| 443 | const aligned_index = alignedIndex(buf.ptr, 0, alignment); |
| 444 | break :aligned_index .{ aligned_index, aligned_index + n > buf.len }; |
| 462 | 445 | }; |
| 463 | 446 | |
| 464 | | { |
| 465 | | var it = last_free; |
| 466 | | while (it) |node| : (it = node.next) { |
| 467 | | last_free = node; |
| 447 | if (need_resize) { |
| 448 | // Ideally we want to use all nodes in `free_list` eventually, |
| 449 | // so even if none fit we'll try to resize the one that was the |
| 450 | // closest to being large enough. |
| 451 | const new_size = mem.alignForward(usize, @sizeOf(Node) + aligned_index + n, 2); |
| 452 | if (arena.child_allocator.rawResize(node.allocatedSliceUnsafe(), .of(Node), new_size, @returnAddress())) { |
| 453 | node.size = .fromInt(new_size); |
| 454 | } else { |
| 455 | arena.pushFreeList(first_free, last_free); |
| 456 | break :from_free_list; // we couldn't find a fitting free node |
| 468 | 457 | } |
| 469 | 458 | } |
| 470 | 459 | |
| 471 | | const node = candidate orelse break :from_free_list; |
| 472 | | const old_next = node.next; |
| 473 | | |
| 474 | 460 | const buf = node.allocatedSliceUnsafe()[@sizeOf(Node)..]; |
| 475 | | const aligned_index = alignedIndex(buf.ptr, 0, alignment); |
| 461 | const old_next = node.next; |
| 476 | 462 | |
| 477 | 463 | node.end_index = aligned_index + n; |
| 478 | 464 | node.next = first_node; |
| 479 | 465 | |
| 480 | 466 | switch (arena.tryPushNode(node)) { |
| 481 | 467 | .success => { |
| 482 | | // finish removing node from free list |
| 468 | // Finish removing node from free list. |
| 483 | 469 | if (prev) |p| p.next = old_next; |
| 484 | | if (node == first_free) first_free = old_next; |
| 485 | | if (node == last_free) last_free = prev; |
| 470 | |
| 471 | // Push remaining stolen free list back onto `arena.state.free_list`. |
| 472 | const new_first_free = if (node == first_free) old_next else first_free; |
| 473 | const new_last_free = if (node == last_free) prev else last_free; |
| 474 | if (new_first_free) |first| { |
| 475 | const last = new_last_free.?; |
| 476 | arena.pushFreeList(first, last); |
| 477 | } |
| 478 | |
| 486 | 479 | return buf[aligned_index..][0..n].ptr; |
| 487 | 480 | }, |
| 488 | 481 | .failure => |old_first_node| { |
| 489 | | cur_first_node = old_first_node; |
| 490 | 482 | // restore free list to as we found it |
| 491 | 483 | node.next = old_next; |
| 492 | | continue :retry; |
| 484 | arena.pushFreeList(first_free, last_free); |
| 485 | |
| 486 | cur_first_node = old_first_node; |
| 487 | continue :retry; // there's a new first node; retry! |
| 493 | 488 | }, |
| 494 | 489 | } |
| 495 | 490 | } |
| ... | ... | @@ -501,16 +496,17 @@ fn alloc(ctx: *anyopaque, n: usize, alignment: Alignment, ret_addr: usize) ?[*]u |
| 501 | 496 | @branchHint(.cold); |
| 502 | 497 | } |
| 503 | 498 | |
| 504 | | const size: usize = size: { |
| 499 | const size: Node.Size = size: { |
| 505 | 500 | const min_size = @sizeOf(Node) + alignment.toByteUnits() + n; |
| 506 | 501 | const big_enough_size = prev_size + min_size + 16; |
| 507 | | break :size mem.alignForward(usize, big_enough_size + big_enough_size / 2, 2); |
| 502 | const size = mem.alignForward(usize, big_enough_size + big_enough_size / 2, 2); |
| 503 | break :size .fromInt(size); |
| 508 | 504 | }; |
| 509 | | const ptr = arena.child_allocator.rawAlloc(size, .of(Node), @returnAddress()) orelse |
| 505 | const ptr = arena.child_allocator.rawAlloc(size.toInt(), .of(Node), @returnAddress()) orelse |
| 510 | 506 | return null; |
| 511 | 507 | const new_node: *Node = @ptrCast(@alignCast(ptr)); |
| 512 | 508 | new_node.* = .{ |
| 513 | | .size = .fromInt(size), |
| 509 | .size = size, |
| 514 | 510 | .end_index = undefined, // set below |
| 515 | 511 | .next = undefined, // set below |
| 516 | 512 | }; |
| ... | ... | @@ -537,91 +533,80 @@ fn alloc(ctx: *anyopaque, n: usize, alignment: Alignment, ret_addr: usize) ?[*]u |
| 537 | 533 | } |
| 538 | 534 | } |
| 539 | 535 | |
| 540 | | fn resize(ctx: *anyopaque, buf: []u8, alignment: Alignment, new_len: usize, ret_addr: usize) bool { |
| 536 | fn resize(ctx: *anyopaque, memory: []u8, alignment: Alignment, new_len: usize, ret_addr: usize) bool { |
| 541 | 537 | const arena: *ArenaAllocator = @ptrCast(@alignCast(ctx)); |
| 542 | 538 | _ = alignment; |
| 543 | 539 | _ = ret_addr; |
| 544 | 540 | |
| 545 | | assert(buf.len > 0); |
| 541 | assert(memory.len > 0); |
| 546 | 542 | assert(new_len > 0); |
| 547 | | if (buf.len == new_len) return true; |
| 548 | 543 | |
| 549 | 544 | const node = arena.loadFirstNode().?; |
| 550 | | const cur_buf_ptr = @as([*]u8, @ptrCast(node)) + @sizeOf(Node); |
| 551 | | |
| 552 | | var cur_end_index = @atomicLoad(usize, &node.end_index, .monotonic); |
| 553 | | while (true) { |
| 554 | | if (cur_buf_ptr + cur_end_index != buf.ptr + buf.len) { |
| 555 | | // It's not the most recent allocation, so it cannot be expanded, |
| 556 | | // but it's fine if they want to make it smaller. |
| 557 | | return new_len <= buf.len; |
| 558 | | } |
| 545 | const buf_ptr = @as([*]u8, @ptrCast(node)) + @sizeOf(Node); |
| 559 | 546 | |
| 560 | | const new_end_index: usize = new_end_index: { |
| 561 | | if (buf.len >= new_len) { |
| 562 | | break :new_end_index cur_end_index - (buf.len - new_len); |
| 563 | | } |
| 564 | | const cur_buf_len: usize = node.loadBuf().len; |
| 565 | | // Saturating arithmetic because `end_index` and `size` are not |
| 566 | | // guaranteed to be in sync. |
| 567 | | if (cur_buf_len -| cur_end_index >= new_len - buf.len) { |
| 568 | | break :new_end_index cur_end_index + (new_len - buf.len); |
| 569 | | } |
| 570 | | return false; |
| 571 | | }; |
| 572 | | |
| 573 | | cur_end_index = @cmpxchgWeak( |
| 574 | | usize, |
| 575 | | &node.end_index, |
| 576 | | cur_end_index, |
| 577 | | new_end_index, |
| 578 | | .monotonic, |
| 579 | | .monotonic, |
| 580 | | ) orelse { |
| 581 | | return true; |
| 582 | | }; |
| 547 | const cur_end_index = @atomicLoad(usize, &node.end_index, .monotonic); |
| 548 | if (buf_ptr + cur_end_index != memory.ptr + memory.len) { |
| 549 | // It's not the most recent allocation, so it cannot be expanded, |
| 550 | // but it's fine if they want to make it smaller. |
| 551 | return new_len <= memory.len; |
| 583 | 552 | } |
| 553 | |
| 554 | const new_end_index: usize = new_end_index: { |
| 555 | if (memory.len >= new_len) { |
| 556 | break :new_end_index cur_end_index - (memory.len - new_len); |
| 557 | } |
| 558 | const cur_buf_len: usize = node.loadBuf().len; |
| 559 | // Saturating arithmetic because `end_index` and `size` are not |
| 560 | // guaranteed to be in sync. |
| 561 | if (cur_buf_len -| cur_end_index >= new_len - memory.len) { |
| 562 | break :new_end_index cur_end_index + (new_len - memory.len); |
| 563 | } |
| 564 | return false; |
| 565 | }; |
| 566 | assert(buf_ptr + new_end_index == memory.ptr + new_len); |
| 567 | |
| 568 | return null == @cmpxchgStrong( |
| 569 | usize, |
| 570 | &node.end_index, |
| 571 | cur_end_index, |
| 572 | new_end_index, |
| 573 | .monotonic, |
| 574 | .monotonic, |
| 575 | ) or |
| 576 | new_len <= memory.len; // Shrinking allocations should always succeed. |
| 584 | 577 | } |
| 585 | 578 | |
| 586 | | fn remap( |
| 587 | | context: *anyopaque, |
| 588 | | memory: []u8, |
| 589 | | alignment: Alignment, |
| 590 | | new_len: usize, |
| 591 | | return_address: usize, |
| 592 | | ) ?[*]u8 { |
| 593 | | return if (resize(context, memory, alignment, new_len, return_address)) memory.ptr else null; |
| 579 | fn remap(ctx: *anyopaque, memory: []u8, alignment: Alignment, new_len: usize, ret_addr: usize) ?[*]u8 { |
| 580 | return if (resize(ctx, memory, alignment, new_len, ret_addr)) memory.ptr else null; |
| 594 | 581 | } |
| 595 | 582 | |
| 596 | | fn free(ctx: *anyopaque, buf: []u8, alignment: Alignment, ret_addr: usize) void { |
| 583 | fn free(ctx: *anyopaque, memory: []u8, alignment: Alignment, ret_addr: usize) void { |
| 597 | 584 | const arena: *ArenaAllocator = @ptrCast(@alignCast(ctx)); |
| 598 | 585 | _ = alignment; |
| 599 | 586 | _ = ret_addr; |
| 600 | 587 | |
| 601 | | assert(buf.len > 0); |
| 588 | assert(memory.len > 0); |
| 602 | 589 | |
| 603 | 590 | const node = arena.loadFirstNode().?; |
| 604 | | const cur_buf_ptr: [*]u8 = @as([*]u8, @ptrCast(node)) + @sizeOf(Node); |
| 591 | const buf_ptr = @as([*]u8, @ptrCast(node)) + @sizeOf(Node); |
| 605 | 592 | |
| 606 | | var cur_end_index = @atomicLoad(usize, &node.end_index, .monotonic); |
| 607 | | while (true) { |
| 608 | | if (cur_buf_ptr + cur_end_index != buf.ptr + buf.len) { |
| 609 | | // Not the most recent allocation; we cannot free it. |
| 610 | | return; |
| 611 | | } |
| 612 | | const new_end_index = cur_end_index - buf.len; |
| 613 | | |
| 614 | | cur_end_index = @cmpxchgWeak( |
| 615 | | usize, |
| 616 | | &node.end_index, |
| 617 | | cur_end_index, |
| 618 | | new_end_index, |
| 619 | | .monotonic, |
| 620 | | .monotonic, |
| 621 | | ) orelse { |
| 622 | | return; |
| 623 | | }; |
| 593 | const cur_end_index = @atomicLoad(usize, &node.end_index, .monotonic); |
| 594 | if (buf_ptr + cur_end_index != memory.ptr + memory.len) { |
| 595 | // Not the most recent allocation; we cannot free it. |
| 596 | return; |
| 624 | 597 | } |
| 598 | |
| 599 | const new_end_index = cur_end_index - memory.len; |
| 600 | assert(buf_ptr + new_end_index == memory.ptr); |
| 601 | |
| 602 | _ = @cmpxchgStrong( |
| 603 | usize, |
| 604 | &node.end_index, |
| 605 | cur_end_index, |
| 606 | new_end_index, |
| 607 | .monotonic, |
| 608 | .monotonic, |
| 609 | ); |
| 625 | 610 | } |
| 626 | 611 | |
| 627 | 612 | const std = @import("std"); |
| ... | ... | @@ -672,3 +657,406 @@ test "reset while retaining a buffer" { |
| 672 | 657 | try std.testing.expect(arena_allocator.state.used_list.?.next == null); |
| 673 | 658 | try std.testing.expectEqual(2, arena_allocator.queryCapacity()); |
| 674 | 659 | } |
| 660 | |
| 661 | test "fuzz" { |
| 662 | @disableInstrumentation(); |
| 663 | if (@import("builtin").single_threaded) return error.SkipZigTest; |
| 664 | |
| 665 | const gpa = std.heap.smp_allocator; |
| 666 | |
| 667 | var arena_state: ArenaAllocator.State = .init; |
| 668 | // No need to deinit arena_state, all allocations are in `sample_buffer`! |
| 669 | |
| 670 | const control_buffer = try gpa.alloc(u8, 64 << 10 << 10); |
| 671 | defer gpa.free(control_buffer); |
| 672 | var control_instance: std.heap.FixedBufferAllocator = .init(control_buffer); |
| 673 | |
| 674 | const sample_buffer = try gpa.alloc(u8, 64 << 10 << 10); |
| 675 | defer gpa.free(sample_buffer); |
| 676 | var sample_instance: FuzzAllocator = .init(sample_buffer); |
| 677 | |
| 678 | var allocs: FuzzContext.Allocs = try .initCapacity(gpa, FuzzContext.max_alloc_count); |
| 679 | defer allocs.deinit(gpa); |
| 680 | |
| 681 | try std.testing.fuzz(FuzzContext.Init{ |
| 682 | .gpa = gpa, |
| 683 | .allocs = &allocs, |
| 684 | .arena_state = &arena_state, |
| 685 | .control_instance = &control_instance, |
| 686 | .sample_instance = &sample_instance, |
| 687 | }, fuzzArenaAllocator, .{}); |
| 688 | } |
| 689 | |
| 690 | fn fuzzArenaAllocator(fuzz_init: FuzzContext.Init, smith: *std.testing.Smith) anyerror!void { |
| 691 | @disableInstrumentation(); |
| 692 | const testing = std.testing; |
| 693 | |
| 694 | // We use a 'fresh' `Threaded` instance every time to reset threadlocals to |
| 695 | // their default values. |
| 696 | |
| 697 | var io_instance: std.Io.Threaded = .init(fuzz_init.gpa, .{}); |
| 698 | defer io_instance.deinit(); |
| 699 | const io = io_instance.io(); |
| 700 | |
| 701 | fuzz_init.sample_instance.prepareFailures(smith); |
| 702 | |
| 703 | const control_allocator = fuzz_init.control_instance.threadSafeAllocator(); |
| 704 | const sample_child_allocator = fuzz_init.sample_instance.allocator(); |
| 705 | |
| 706 | var arena_instance = fuzz_init.arena_state.*.promote(sample_child_allocator); |
| 707 | defer fuzz_init.arena_state.* = arena_instance.state; |
| 708 | |
| 709 | var ctx: FuzzContext = .init( |
| 710 | io, |
| 711 | control_allocator, |
| 712 | arena_instance.allocator(), |
| 713 | fuzz_init.allocs, |
| 714 | ); |
| 715 | defer ctx.deinit(); |
| 716 | |
| 717 | ctx.rwl.lockUncancelable(io); |
| 718 | |
| 719 | var group: std.Io.Group = .init; |
| 720 | defer group.cancel(io); |
| 721 | |
| 722 | var n_actions: usize = 0; |
| 723 | while (!smith.eosWeightedSimple(99, 1) and n_actions < FuzzContext.max_action_count) { |
| 724 | errdefer comptime unreachable; |
| 725 | |
| 726 | const ActionTag = @typeInfo(FuzzContext.Action).@"union".tag_type.?; |
| 727 | const weights: []const testing.Smith.Weight = weights: { |
| 728 | if (ctx.allocs.len == ctx.allocs.capacity) |
| 729 | break :weights &.{ |
| 730 | .value(ActionTag, .resize, 1), |
| 731 | .value(ActionTag, .remap, 1), |
| 732 | .value(ActionTag, .free, 1), |
| 733 | }; |
| 734 | break :weights testing.Smith.baselineWeights(ActionTag) ++ |
| 735 | .{testing.Smith.Weight.value(ActionTag, .alloc, 2)}; |
| 736 | }; |
| 737 | const action: FuzzContext.Action = switch (smith.valueWeighted(ActionTag, weights)) { |
| 738 | .alloc => action: { |
| 739 | const alloc_index = ctx.allocs.addOneBounded() catch continue; |
| 740 | ctx.allocs.items(.len)[alloc_index] = .free; |
| 741 | break :action .{ .alloc = .{ |
| 742 | .len = nextLen(smith), |
| 743 | .alignment = smith.valueRangeAtMost( |
| 744 | Alignment, |
| 745 | .@"1", |
| 746 | .fromByteUnits(2 * std.heap.page_size_max), |
| 747 | ), |
| 748 | .index = alloc_index, |
| 749 | } }; |
| 750 | }, |
| 751 | .resize => .{ .resize = .{ .new_len = nextLen(smith) } }, |
| 752 | .remap => .{ .remap = .{ .new_len = nextLen(smith) } }, |
| 753 | .free => .free, |
| 754 | }; |
| 755 | group.concurrent(io, FuzzContext.doOneAction, .{ &ctx, action }) catch break; |
| 756 | n_actions += 1; |
| 757 | } |
| 758 | |
| 759 | ctx.rwl.unlock(io); |
| 760 | |
| 761 | try group.await(io); |
| 762 | try ctx.check(); |
| 763 | |
| 764 | // This also covers the `deinit` logic since `free_all` uses it internally. |
| 765 | |
| 766 | const old_capacity = arena_instance.queryCapacity(); |
| 767 | const reset_mode: ResetMode = switch (smith.value(@typeInfo(ResetMode).@"union".tag_type.?)) { |
| 768 | .free_all => .free_all, |
| 769 | .retain_capacity => .retain_capacity, |
| 770 | .retain_with_limit => .{ .retain_with_limit = smith.value(usize) }, |
| 771 | }; |
| 772 | const ok = arena_instance.reset(reset_mode); |
| 773 | const new_capacity = arena_instance.queryCapacity(); |
| 774 | switch (reset_mode) { |
| 775 | .free_all => { |
| 776 | try testing.expect(ok); |
| 777 | try testing.expectEqual(0, new_capacity); |
| 778 | fuzz_init.sample_instance.reset(); |
| 779 | }, |
| 780 | .retain_with_limit => |limit| if (ok) try testing.expect(new_capacity <= limit), |
| 781 | .retain_capacity => if (ok) try testing.expectEqual(old_capacity, new_capacity), |
| 782 | } |
| 783 | |
| 784 | fuzz_init.control_instance.reset(); |
| 785 | fuzz_init.allocs.clearRetainingCapacity(); |
| 786 | } |
| 787 | fn nextLen(smith: *std.testing.Smith) usize { |
| 788 | @disableInstrumentation(); |
| 789 | return usizeRange(smith, 1, 16 << 10 << 10); |
| 790 | } |
| 791 | fn usizeRange(smith: *std.testing.Smith, at_least: usize, at_most: usize) usize { |
| 792 | @disableInstrumentation(); |
| 793 | const Int = @Int(.unsigned, @min(64, @bitSizeOf(usize))); |
| 794 | return smith.valueRangeAtMost(Int, @intCast(at_least), @intCast(at_most)); |
| 795 | } |
| 796 | |
| 797 | const FuzzContext = struct { |
| 798 | io: std.Io, |
| 799 | rwl: std.Io.RwLock, |
| 800 | |
| 801 | control_allocator: Allocator, |
| 802 | sample_allocator: Allocator, |
| 803 | |
| 804 | allocs: *Allocs, |
| 805 | |
| 806 | const max_alloc_count = 4096; |
| 807 | const max_action_count = 2 * max_alloc_count; |
| 808 | |
| 809 | const Allocs = std.MultiArrayList(struct { |
| 810 | control_ptr: [*]u8, |
| 811 | sample_ptr: [*]u8, |
| 812 | len: Len, |
| 813 | alignment: Alignment, |
| 814 | }); |
| 815 | |
| 816 | const Len = enum(usize) { |
| 817 | free = std.math.maxInt(usize), |
| 818 | _, |
| 819 | }; |
| 820 | |
| 821 | const Action = union(enum(u8)) { |
| 822 | alloc: struct { len: usize, alignment: Alignment, index: usize }, |
| 823 | resize: struct { new_len: usize }, |
| 824 | remap: struct { new_len: usize }, |
| 825 | free, |
| 826 | }; |
| 827 | |
| 828 | threadlocal var tls_next: u8 = 0; |
| 829 | threadlocal var tls_last_index: ?usize = null; |
| 830 | |
| 831 | const Init = struct { |
| 832 | gpa: Allocator, |
| 833 | allocs: *FuzzContext.Allocs, |
| 834 | arena_state: *ArenaAllocator.State, |
| 835 | control_instance: *std.heap.FixedBufferAllocator, |
| 836 | sample_instance: *FuzzAllocator, |
| 837 | }; |
| 838 | |
| 839 | fn init( |
| 840 | io: std.Io, |
| 841 | control_allocator: Allocator, |
| 842 | sample_allocator: Allocator, |
| 843 | allocs: *Allocs, |
| 844 | ) FuzzContext { |
| 845 | @disableInstrumentation(); |
| 846 | return .{ |
| 847 | .io = io, |
| 848 | .rwl = .init, |
| 849 | .control_allocator = control_allocator, |
| 850 | .sample_allocator = sample_allocator, |
| 851 | .allocs = allocs, |
| 852 | }; |
| 853 | } |
| 854 | |
| 855 | fn deinit(ctx: *FuzzContext) void { |
| 856 | @disableInstrumentation(); |
| 857 | ctx.* = undefined; |
| 858 | } |
| 859 | |
| 860 | fn check(ctx: *const FuzzContext) !void { |
| 861 | @disableInstrumentation(); |
| 862 | for (0..ctx.allocs.len) |index| { |
| 863 | const len: usize = switch (ctx.allocs.items(.len)[index]) { |
| 864 | .free => continue, |
| 865 | _ => |len| @intFromEnum(len), |
| 866 | }; |
| 867 | const control = ctx.allocs.items(.control_ptr)[index][0..len]; |
| 868 | const sample = ctx.allocs.items(.sample_ptr)[index][0..len]; |
| 869 | try std.testing.expectEqualSlices(u8, control, sample); |
| 870 | } |
| 871 | } |
| 872 | |
| 873 | fn doOneAction(ctx: *FuzzContext, action: Action) std.Io.Cancelable!void { |
| 874 | @disableInstrumentation(); |
| 875 | ctx.rwl.lockSharedUncancelable(ctx.io); |
| 876 | defer ctx.rwl.unlockShared(ctx.io); |
| 877 | |
| 878 | switch (action) { |
| 879 | .alloc => |act| ctx.doOneAlloc(act.len, act.alignment, act.index), |
| 880 | .resize => |act| ctx.doOneResize(act.new_len), |
| 881 | .remap => |act| ctx.doOneRemap(act.new_len), |
| 882 | .free => ctx.doOneFree(), |
| 883 | } |
| 884 | } |
| 885 | |
| 886 | fn doOneAlloc(ctx: *FuzzContext, len: usize, alignment: Alignment, index: usize) void { |
| 887 | @disableInstrumentation(); |
| 888 | assert(ctx.allocs.items(.len)[index] == .free); |
| 889 | |
| 890 | const control_ptr = ctx.control_allocator.rawAlloc(len, alignment, @returnAddress()) orelse |
| 891 | return; |
| 892 | const sample_ptr = ctx.sample_allocator.rawAlloc(len, alignment, @returnAddress()) orelse { |
| 893 | ctx.control_allocator.rawFree(control_ptr[0..len], alignment, @returnAddress()); |
| 894 | return; |
| 895 | }; |
| 896 | |
| 897 | ctx.allocs.set(index, .{ |
| 898 | .control_ptr = control_ptr, |
| 899 | .sample_ptr = sample_ptr, |
| 900 | .len = @enumFromInt(len), |
| 901 | .alignment = alignment, |
| 902 | }); |
| 903 | |
| 904 | for (control_ptr[0..len], sample_ptr[0..len]) |*control, *sample| { |
| 905 | control.* = tls_next; |
| 906 | sample.* = tls_next; |
| 907 | tls_next +%= 1; |
| 908 | } |
| 909 | |
| 910 | tls_last_index = index; |
| 911 | } |
| 912 | fn doOneResize(ctx: *FuzzContext, new_len: usize) void { |
| 913 | @disableInstrumentation(); |
| 914 | const index = tls_last_index orelse return; |
| 915 | const len = ctx.allocs.items(.len)[index]; |
| 916 | assert(len != .free); |
| 917 | const memory = ctx.allocs.items(.sample_ptr)[index][0..@intFromEnum(len)]; |
| 918 | const alignment = ctx.allocs.items(.alignment)[index]; |
| 919 | |
| 920 | assert(alignment.check(@intFromPtr(ctx.allocs.items(.control_ptr)[index]))); |
| 921 | assert(alignment.check(@intFromPtr(ctx.allocs.items(.sample_ptr)[index]))); |
| 922 | |
| 923 | // Since `resize` is fallible, we have to ensure that `control_allocator` |
| 924 | // is always successful by reserving the memory we need beforehand. |
| 925 | const new_control_ptr = ctx.control_allocator.rawAlloc(new_len, alignment, @returnAddress()) orelse |
| 926 | return; |
| 927 | if (ctx.sample_allocator.rawResize(memory, alignment, new_len, @returnAddress())) { |
| 928 | const old_control = ctx.allocs.items(.control_ptr)[index][0..memory.len]; |
| 929 | const overlap = @min(memory.len, new_len); |
| 930 | @memcpy(new_control_ptr[0..overlap], old_control[0..overlap]); |
| 931 | ctx.control_allocator.rawFree(old_control, alignment, @returnAddress()); |
| 932 | } else { |
| 933 | ctx.control_allocator.rawFree(new_control_ptr[0..new_len], alignment, @returnAddress()); |
| 934 | return; |
| 935 | } |
| 936 | |
| 937 | ctx.allocs.set(index, .{ |
| 938 | .control_ptr = new_control_ptr, |
| 939 | .sample_ptr = memory.ptr, |
| 940 | .len = @enumFromInt(new_len), |
| 941 | .alignment = alignment, |
| 942 | }); |
| 943 | |
| 944 | if (new_len > memory.len) { |
| 945 | for ( |
| 946 | ctx.allocs.items(.control_ptr)[index][memory.len..new_len], |
| 947 | ctx.allocs.items(.sample_ptr)[index][memory.len..new_len], |
| 948 | ) |*control, *sample| { |
| 949 | control.* = tls_next; |
| 950 | sample.* = tls_next; |
| 951 | tls_next +%= 1; |
| 952 | } |
| 953 | } |
| 954 | } |
| 955 | fn doOneRemap(ctx: *FuzzContext, new_len: usize) void { |
| 956 | @disableInstrumentation(); |
| 957 | return doOneResize(ctx, new_len); |
| 958 | } |
| 959 | fn doOneFree(ctx: *FuzzContext) void { |
| 960 | @disableInstrumentation(); |
| 961 | const index = tls_last_index orelse return; |
| 962 | const len = ctx.allocs.items(.len)[index]; |
| 963 | assert(len != .free); |
| 964 | const memory = ctx.allocs.items(.sample_ptr)[index][0..@intFromEnum(len)]; |
| 965 | const alignment = ctx.allocs.items(.alignment)[index]; |
| 966 | |
| 967 | assert(alignment.check(@intFromPtr(ctx.allocs.items(.control_ptr)[index]))); |
| 968 | assert(alignment.check(@intFromPtr(ctx.allocs.items(.sample_ptr)[index]))); |
| 969 | |
| 970 | ctx.control_allocator.rawFree(ctx.allocs.items(.control_ptr)[index][0..memory.len], alignment, @returnAddress()); |
| 971 | ctx.sample_allocator.rawFree(ctx.allocs.items(.sample_ptr)[index][0..memory.len], alignment, @returnAddress()); |
| 972 | |
| 973 | ctx.allocs.set(index, .{ |
| 974 | .control_ptr = undefined, |
| 975 | .sample_ptr = undefined, |
| 976 | .len = .free, |
| 977 | .alignment = undefined, |
| 978 | }); |
| 979 | |
| 980 | tls_last_index = null; |
| 981 | } |
| 982 | }; |
| 983 | |
| 984 | const FuzzAllocator = struct { |
| 985 | fba: std.heap.FixedBufferAllocator, |
| 986 | spurious_failures: [256]u8, |
| 987 | index: u8, |
| 988 | |
| 989 | fn init(buffer: []u8) FuzzAllocator { |
| 990 | @disableInstrumentation(); |
| 991 | return .{ |
| 992 | .fba = .init(buffer), |
| 993 | .spurious_failures = undefined, // set with `preprepareFailures` |
| 994 | .index = 0, |
| 995 | }; |
| 996 | } |
| 997 | |
| 998 | fn prepareFailures(fa: *FuzzAllocator, smith: *std.testing.Smith) void { |
| 999 | @disableInstrumentation(); |
| 1000 | const bool_weights: []const std.testing.Smith.Weight = &.{ |
| 1001 | .value(u8, 0, 10), |
| 1002 | .value(u8, 1, 1), |
| 1003 | }; |
| 1004 | smith.bytesWeighted(&fa.spurious_failures, bool_weights); |
| 1005 | fa.index = 0; |
| 1006 | } |
| 1007 | |
| 1008 | fn reset(fa: *FuzzAllocator) void { |
| 1009 | @disableInstrumentation(); |
| 1010 | fa.fba.reset(); |
| 1011 | } |
| 1012 | |
| 1013 | fn allocator(fa: *FuzzAllocator) Allocator { |
| 1014 | @disableInstrumentation(); |
| 1015 | return .{ |
| 1016 | .ptr = fa, |
| 1017 | .vtable = &.{ |
| 1018 | .alloc = FuzzAllocator.alloc, |
| 1019 | .resize = FuzzAllocator.resize, |
| 1020 | .remap = FuzzAllocator.remap, |
| 1021 | .free = FuzzAllocator.free, |
| 1022 | }, |
| 1023 | }; |
| 1024 | } |
| 1025 | |
| 1026 | fn alloc(ctx: *anyopaque, len: usize, alignment: Alignment, ret_addr: usize) ?[*]u8 { |
| 1027 | @disableInstrumentation(); |
| 1028 | const fa: *FuzzAllocator = @ptrCast(@alignCast(ctx)); |
| 1029 | _ = ret_addr; |
| 1030 | |
| 1031 | const index = @atomicRmw(u8, &fa.index, .Add, 1, .monotonic); |
| 1032 | if (fa.spurious_failures[index] != 0) return null; |
| 1033 | return fa.fba.threadSafeAllocator().rawAlloc(len, alignment, @returnAddress()); |
| 1034 | } |
| 1035 | |
| 1036 | fn resize(ctx: *anyopaque, memory: []u8, alignment: Alignment, new_len: usize, ret_addr: usize) bool { |
| 1037 | @disableInstrumentation(); |
| 1038 | const fa: *FuzzAllocator = @ptrCast(@alignCast(ctx)); |
| 1039 | _ = ret_addr; |
| 1040 | |
| 1041 | const index = @atomicRmw(u8, &fa.index, .Add, 1, .monotonic); |
| 1042 | if (fa.spurious_failures[index] != 0) return false; |
| 1043 | return fa.fba.threadSafeAllocator().rawResize(memory, alignment, new_len, @returnAddress()); |
| 1044 | } |
| 1045 | |
| 1046 | fn remap(ctx: *anyopaque, memory: []u8, alignment: Alignment, new_len: usize, ret_addr: usize) ?[*]u8 { |
| 1047 | @disableInstrumentation(); |
| 1048 | const fa: *FuzzAllocator = @ptrCast(@alignCast(ctx)); |
| 1049 | _ = ret_addr; |
| 1050 | |
| 1051 | const index = @atomicRmw(u8, &fa.index, .Add, 1, .monotonic); |
| 1052 | if (fa.spurious_failures[index] != 0) return null; |
| 1053 | return fa.fba.threadSafeAllocator().rawRemap(memory, alignment, new_len, @returnAddress()); |
| 1054 | } |
| 1055 | |
| 1056 | fn free(ctx: *anyopaque, memory: []u8, alignment: Alignment, ret_addr: usize) void { |
| 1057 | @disableInstrumentation(); |
| 1058 | const fa: *FuzzAllocator = @ptrCast(@alignCast(ctx)); |
| 1059 | _ = ret_addr; |
| 1060 | return fa.fba.threadSafeAllocator().rawFree(memory, alignment, @returnAddress()); |
| 1061 | } |
| 1062 | }; |
Andrew Kelley <andrew@ziglang.org> 2026-03-11 03:00:07+01:00