commit cf75cad899069d67d50e6d08160b998b7cba16dc (tree)
parent 4334dbb9a5ddfa58a06f3ef7759927e2cb38e65b
Author: Martin Wickham <spexguy070@gmail.com>
Date: Mon, 30 Aug 2021 13:01:37 -0500
Add comptime memory tests
Diffstat:
2 files changed, 319 insertions(+), 0 deletions(-)
diff --git a/test/behavior.zig b/test/behavior.zig
@@ -89,6 +89,8 @@ test {
_ = @import("behavior/byval_arg_var.zig");
_ = @import("behavior/call.zig");
_ = @import("behavior/cast_stage1.zig");
+ // When these tests pass, #9646 can be closed.
+ // _ = @import("behavior/comptime_memory.zig");
_ = @import("behavior/const_slice_child.zig");
_ = @import("behavior/defer.zig");
_ = @import("behavior/enum.zig");
diff --git a/test/behavior/comptime_memory.zig b/test/behavior/comptime_memory.zig
@@ -0,0 +1,317 @@
+const endian = @import("builtin").cpu.arch.endian();
+const testing = @import("std").testing;
+const ptr_size = @sizeOf(usize);
+
+test "type pun signed and unsigned as single pointer" {
+ comptime {
+ var x: u32 = 0;
+ const y = @ptrCast(*i32, &x);
+ y.* = -1;
+ try testing.expectEqual(@as(u32, 0xFFFFFFFF), x);
+ }
+}
+
+test "type pun signed and unsigned as many pointer" {
+ comptime {
+ var x: u32 = 0;
+ const y = @ptrCast([*]i32, &x);
+ y[0] = -1;
+ try testing.expectEqual(@as(u32, 0xFFFFFFFF), x);
+ }
+}
+
+test "type pun signed and unsigned as array pointer" {
+ comptime {
+ var x: u32 = 0;
+ const y = @ptrCast(*[1]i32, &x);
+ y[0] = -1;
+ try testing.expectEqual(@as(u32, 0xFFFFFFFF), x);
+ }
+}
+
+test "type pun signed and unsigned as offset many pointer" {
+ comptime {
+ var x: u32 = 0;
+ var y = @ptrCast([*]i32, &x);
+ y -= 10;
+ y[10] = -1;
+ try testing.expectEqual(@as(u32, 0xFFFFFFFF), x);
+ }
+}
+
+test "type pun signed and unsigned as array pointer" {
+ comptime {
+ var x: u32 = 0;
+ const y = @ptrCast([*]i32, &x) - 10;
+ const z: *[15]i32 = y[0..15];
+ z[10] = -1;
+ try testing.expectEqual(@as(u32, 0xFFFFFFFF), x);
+ }
+}
+
+test "type pun value and struct" {
+ comptime {
+ const StructOfU32 = extern struct { x: u32 };
+ var inst: StructOfU32 = .{ .x = 0 };
+ @ptrCast(*i32, &inst.x).* = -1;
+ try testing.expectEqual(@as(u32, 0xFFFFFFFF), inst.x);
+ @ptrCast(*i32, &inst).* = -2;
+ try testing.expectEqual(@as(u32, 0xFFFFFFFE), inst.x);
+ }
+}
+
+fn bigToNativeEndian(comptime T: type, v: T) T {
+ return if (endian == .Big) v else @byteSwap(T, v);
+}
+test "type pun endianness" {
+ comptime {
+ const StructOfBytes = extern struct { x: [4]u8 };
+ var inst: StructOfBytes = .{ .x = [4]u8{ 0, 0, 0, 0 } };
+ const structPtr = @ptrCast(*align(1) u32, &inst);
+ const arrayPtr = @ptrCast(*align(1) u32, &inst.x);
+ inst.x[0] = 0xFE;
+ inst.x[2] = 0xBE;
+ try testing.expectEqual(bigToNativeEndian(u32, 0xFE00BE00), structPtr.*);
+ try testing.expectEqual(bigToNativeEndian(u32, 0xFE00BE00), arrayPtr.*);
+ structPtr.* = bigToNativeEndian(u32, 0xDEADF00D);
+ try testing.expectEqual(bigToNativeEndian(u32, 0xDEADF00D), structPtr.*);
+ try testing.expectEqual(bigToNativeEndian(u32, 0xDEADF00D), arrayPtr.*);
+ try testing.expectEqual(@as(u8, 0xDE), inst.x[0]);
+ try testing.expectEqual(@as(u8, 0xAD), inst.x[1]);
+ try testing.expectEqual(@as(u8, 0xF0), inst.x[2]);
+ try testing.expectEqual(@as(u8, 0x0D), inst.x[3]);
+ }
+}
+
+const Bits = packed struct {
+ // Note: This struct has only single byte words so it
+ // doesn't need to be byte swapped.
+ p0: u1,
+ p1: u4,
+ p2: u3,
+ p3: u2,
+ p4: u6,
+ p5: u8,
+ p6: u7,
+ p7: u1,
+};
+const ShuffledBits = packed struct {
+ p1: u4,
+ p3: u2,
+ p7: u1,
+ p0: u1,
+ p5: u8,
+ p2: u3,
+ p6: u7,
+ p4: u6,
+};
+fn shuffle(ptr: usize, comptime From: type, comptime To: type) usize {
+ if (@sizeOf(From) != @sizeOf(To))
+ @compileError("Mismatched sizes! " ++ @typeName(From) ++ " and " ++ @typeName(To) ++ " must have the same size!");
+ const array_len = @divExact(ptr_size, @sizeOf(From));
+ var result: usize = 0;
+ const pSource = @ptrCast(*align(1) const [array_len]From, &ptr);
+ const pResult = @ptrCast(*align(1) [array_len]To, &result);
+ var i: usize = 0;
+ while (i < array_len) : (i += 1) {
+ inline for (@typeInfo(To).Struct.fields) |f| {
+ @field(pResult[i], f.name) = @field(pSource[i], f.name);
+ }
+ }
+ return result;
+}
+
+fn doTypePunBitsTest(as_bits: *Bits) !void {
+ const as_u32 = @ptrCast(*align(1) u32, as_bits);
+ const as_bytes = @ptrCast(*[4]u8, as_bits);
+ as_u32.* = bigToNativeEndian(u32, 0xB0A7DEED);
+ try testing.expectEqual(@as(u1, 0x00), as_bits.p0);
+ try testing.expectEqual(@as(u4, 0x08), as_bits.p1);
+ try testing.expectEqual(@as(u3, 0x05), as_bits.p2);
+ try testing.expectEqual(@as(u2, 0x03), as_bits.p3);
+ try testing.expectEqual(@as(u6, 0x29), as_bits.p4);
+ try testing.expectEqual(@as(u8, 0xDE), as_bits.p5);
+ try testing.expectEqual(@as(u7, 0x6D), as_bits.p6);
+ try testing.expectEqual(@as(u1, 0x01), as_bits.p7);
+
+ as_bits.p6 = 0x2D;
+ as_bits.p1 = 0x0F;
+ try testing.expectEqual(bigToNativeEndian(u32, 0xBEA7DEAD), as_u32.*);
+
+ // clobbering one bit doesn't clobber the word
+ as_bits.p7 = undefined;
+ try testing.expectEqual(@as(u7, 0x2D), as_bits.p6);
+ // even when read as a whole
+ const u = as_u32.*;
+ _ = u; // u is undefined
+ try testing.expectEqual(@as(u7, 0x2D), as_bits.p6);
+ // or if a field which shares the byte is modified
+ as_bits.p6 = 0x6D;
+ try testing.expectEqual(@as(u7, 0x6D), as_bits.p6);
+
+ // but overwriting the undefined will clear it
+ as_bytes[3] = 0xAF;
+ try testing.expectEqual(bigToNativeEndian(u32, 0xBEA7DEAF), as_u32.*);
+}
+
+test "type pun bits" {
+ comptime {
+ var v: u32 = undefined;
+ try doTypePunBitsTest(@ptrCast(*Bits, &v));
+ }
+}
+
+const imports = struct {
+ var global_u32: u32 = 0;
+};
+
+// Make sure lazy values work on their own, before getting into more complex tests
+test "basic pointer preservation" {
+ comptime {
+ const lazy_address = @ptrToInt(&imports.global_u32);
+ try testing.expectEqual(@ptrToInt(&imports.global_u32), lazy_address);
+ try testing.expectEqual(&imports.global_u32, @intToPtr(*u32, lazy_address));
+ }
+}
+
+test "byte copy preserves linker value" {
+ const ct_value = comptime blk: {
+ const lazy = &imports.global_u32;
+ var result: *u32 = undefined;
+ const pSource = @ptrCast(*const [ptr_size]u8, &lazy);
+ const pResult = @ptrCast(*[ptr_size]u8, &result);
+ var i: usize = 0;
+ while (i < ptr_size) : (i += 1) {
+ pResult[i] = pSource[i];
+ try testing.expectEqual(pSource[i], pResult[i]);
+ }
+ try testing.expectEqual(&imports.global_u32, result);
+ break :blk result;
+ };
+
+ try testing.expectEqual(&imports.global_u32, ct_value);
+}
+
+test "unordered byte copy preserves linker value" {
+ const ct_value = comptime blk: {
+ const lazy = &imports.global_u32;
+ var result: *u32 = undefined;
+ const pSource = @ptrCast(*const [ptr_size]u8, &lazy);
+ const pResult = @ptrCast(*[ptr_size]u8, &result);
+ if (ptr_size > 8) @compileError("This array needs to be expanded for platform with very big pointers");
+ const shuffled_indices = [_]usize{ 4, 5, 2, 6, 1, 3, 0, 7 };
+ for (shuffled_indices) |i| {
+ pResult[i] = pSource[i];
+ try testing.expectEqual(pSource[i], pResult[i]);
+ }
+ try testing.expectEqual(&imports.global_u32, result);
+ break :blk result;
+ };
+
+ try testing.expectEqual(&imports.global_u32, ct_value);
+}
+
+test "shuffle chunks of linker value" {
+ const lazy_address = @ptrToInt(&imports.global_u32);
+ const shuffled1_rt = shuffle(lazy_address, Bits, ShuffledBits);
+ const unshuffled1_rt = shuffle(shuffled1_rt, ShuffledBits, Bits);
+ try testing.expectEqual(lazy_address, unshuffled1_rt);
+ const shuffled1_ct = comptime shuffle(lazy_address, Bits, ShuffledBits);
+ const shuffled1_ct_2 = comptime shuffle(lazy_address, Bits, ShuffledBits);
+ comptime try testing.expectEqual(shuffled1_ct, shuffled1_ct_2);
+ const unshuffled1_ct = comptime shuffle(shuffled1_ct, ShuffledBits, Bits);
+ comptime try testing.expectEqual(lazy_address, unshuffled1_ct);
+ try testing.expectEqual(shuffled1_ct, shuffled1_rt);
+}
+
+test "dance on linker values" {
+ comptime {
+ var arr: [2]usize = undefined;
+ arr[0] = @ptrToInt(&imports.global_u32);
+ arr[1] = @ptrToInt(&imports.global_u32);
+
+ const weird_ptr = @ptrCast([*]Bits, @ptrCast([*]u8, &arr) + @sizeOf(usize) - 3);
+ try doTypePunBitsTest(&weird_ptr[0]);
+ if (ptr_size > @sizeOf(Bits))
+ try doTypePunBitsTest(&weird_ptr[1]);
+
+ var arr_bytes = @ptrCast(*[2][ptr_size]u8, &arr);
+
+ var rebuilt_bytes: [ptr_size]u8 = undefined;
+ var i: usize = 0;
+ while (i < ptr_size - 3) : (i += 1) {
+ rebuilt_bytes[i] = arr_bytes[0][i];
+ }
+ while (i < ptr_size) : (i += 1) {
+ rebuilt_bytes[i] = arr_bytes[1][i];
+ }
+
+ try testing.expectEqual(&imports.global_u32, @intToPtr(*u32, @bitCast(usize, rebuilt_bytes)));
+ }
+}
+
+test "offset array ptr by element size" {
+ comptime {
+ const VirtualStruct = struct { x: u32 };
+ var arr: [4]VirtualStruct = .{
+ .{ .x = bigToNativeEndian(u32, 0x0004080c) },
+ .{ .x = bigToNativeEndian(u32, 0x0105090d) },
+ .{ .x = bigToNativeEndian(u32, 0x02060a0e) },
+ .{ .x = bigToNativeEndian(u32, 0x03070b0f) },
+ };
+
+ const address = @ptrToInt(&arr);
+ try testing.expectEqual(@ptrToInt(&arr[0]), address);
+ try testing.expectEqual(@ptrToInt(&arr[0]) + 10, address + 10);
+ try testing.expectEqual(@ptrToInt(&arr[1]), address + @sizeOf(VirtualStruct));
+ try testing.expectEqual(@ptrToInt(&arr[2]), address + 2 * @sizeOf(VirtualStruct));
+ try testing.expectEqual(@ptrToInt(&arr[3]), address + @sizeOf(VirtualStruct) * 3);
+
+ const secondElement = @intToPtr(*VirtualStruct, @ptrToInt(&arr[0]) + 2 * @sizeOf(VirtualStruct));
+ try testing.expectEqual(bigToNativeEndian(u32, 0x02060a0e), secondElement.x);
+ }
+}
+
+test "offset instance by field size" {
+ comptime {
+ const VirtualStruct = struct { x: u32, y: u32, z: u32, w: u32 };
+ var inst = VirtualStruct{ .x = 0, .y = 1, .z = 2, .w = 3 };
+
+ var ptr = @ptrToInt(&inst);
+ ptr -= 4;
+ ptr += @offsetOf(VirtualStruct, "x");
+ try testing.expectEqual(@as(u32, 0), @intToPtr([*]u32, ptr)[1]);
+ ptr -= @offsetOf(VirtualStruct, "x");
+ ptr += @offsetOf(VirtualStruct, "y");
+ try testing.expectEqual(@as(u32, 1), @intToPtr([*]u32, ptr)[1]);
+ ptr = ptr - @offsetOf(VirtualStruct, "y") + @offsetOf(VirtualStruct, "z");
+ try testing.expectEqual(@as(u32, 2), @intToPtr([*]u32, ptr)[1]);
+ ptr = @ptrToInt(&inst.z) - 4 - @offsetOf(VirtualStruct, "z");
+ ptr += @offsetOf(VirtualStruct, "w");
+ try testing.expectEqual(@as(u32, 3), @intToPtr(*u32, ptr + 4).*);
+ }
+}
+
+test "offset field ptr by enclosing array element size" {
+ comptime {
+ const VirtualStruct = struct { x: u32 };
+ var arr: [4]VirtualStruct = .{
+ .{ .x = bigToNativeEndian(u32, 0x0004080c) },
+ .{ .x = bigToNativeEndian(u32, 0x0105090d) },
+ .{ .x = bigToNativeEndian(u32, 0x02060a0e) },
+ .{ .x = bigToNativeEndian(u32, 0x03070b0f) },
+ };
+
+ var i: usize = 0;
+ while (i < 4) : (i += 1) {
+ var ptr: [*]u8 = @ptrCast([*]u8, &arr[0]);
+ ptr += i;
+ ptr += @offsetOf(VirtualStruct, "x");
+ var j: usize = 0;
+ while (j < 4) : (j += 1) {
+ const base = ptr + j * @sizeOf(VirtualStruct);
+ try testing.expectEqual(@intCast(u8, i * 4 + j), base[0]);
+ }
+ }
+ }
+}
