| ... | ... | @@ -459,3 +459,77 @@ test "write empty array to end" { |
| 459 | 459 | array[5..5].* = [_]u8{}; |
| 460 | 460 | try testing.expectEqualStrings("hello", &array); |
| 461 | 461 | } |
| 462 | |
| 463 | fn doublePtrTest() !void { |
| 464 | var a: u32 = 0; |
| 465 | const ptr = &a; |
| 466 | const double_ptr = &ptr; |
| 467 | setDoublePtr(double_ptr, 1); |
| 468 | setDoublePtr(double_ptr, 2); |
| 469 | setDoublePtr(double_ptr, 1); |
| 470 | try std.testing.expect(a == 1); |
| 471 | } |
| 472 | fn setDoublePtr(ptr: *const *const u32, value: u32) void { |
| 473 | setPtr(ptr.*, value); |
| 474 | } |
| 475 | fn setPtr(ptr: *const u32, value: u32) void { |
| 476 | const mut_ptr: *u32 = @constCast(ptr); |
| 477 | mut_ptr.* = value; |
| 478 | } |
| 479 | test "double pointer can mutate comptime state" { |
| 480 | try comptime doublePtrTest(); |
| 481 | } |
| 482 | |
| 483 | fn GenericIntApplier( |
| 484 | comptime Context: type, |
| 485 | comptime applyFn: fn (context: Context, arg: u32) void, |
| 486 | ) type { |
| 487 | return struct { |
| 488 | context: Context, |
| 489 | |
| 490 | const Self = @This(); |
| 491 | |
| 492 | inline fn any(self: *const Self) IntApplier { |
| 493 | return .{ |
| 494 | .context = @ptrCast(&self.context), |
| 495 | .applyFn = typeErasedApplyFn, |
| 496 | }; |
| 497 | } |
| 498 | |
| 499 | fn typeErasedApplyFn(context: *const anyopaque, arg: u32) void { |
| 500 | const ptr: *const Context = @alignCast(@ptrCast(context)); |
| 501 | applyFn(ptr.*, arg); |
| 502 | } |
| 503 | }; |
| 504 | } |
| 505 | const IntApplier = struct { |
| 506 | context: *const anyopaque, |
| 507 | applyFn: *const fn (context: *const anyopaque, arg: u32) void, |
| 508 | |
| 509 | fn apply(ia: IntApplier, arg: u32) void { |
| 510 | ia.applyFn(ia.context, arg); |
| 511 | } |
| 512 | }; |
| 513 | const Accumulator = struct { |
| 514 | value: u32, |
| 515 | |
| 516 | const Applier = GenericIntApplier(*u32, add); |
| 517 | |
| 518 | fn applier(a: *Accumulator) Applier { |
| 519 | return .{ .context = &a.value }; |
| 520 | } |
| 521 | |
| 522 | fn add(context: *u32, arg: u32) void { |
| 523 | context.* += arg; |
| 524 | } |
| 525 | }; |
| 526 | fn fieldPtrTest() u32 { |
| 527 | var a: Accumulator = .{ .value = 0 }; |
| 528 | const applier = a.applier(); |
| 529 | applier.any().apply(1); |
| 530 | applier.any().apply(1); |
| 531 | return a.value; |
| 532 | } |
| 533 | test "pointer in aggregate field can mutate comptime state" { |
| 534 | try comptime std.testing.expect(fieldPtrTest() == 2); |
| 535 | } |
Veikka Tuominen <git@vexu.eu> 2024-01-29 12:43:17+02:00
src