Commit e6ebdcb82ed9fd226ef18670115b8b2617c0a392 | zig

author	Cody Tapscott <topolarity@tapscott.me> 2022-10-10 23:57:48-07:00
committer	Andrew Kelley <andrew@ziglang.org> 2022-10-11 15:42:01-04:00
log	e6ebdcb82ed9fd226ef18670115b8b2617c0a392
tree	1015c798799df19173c85908dec4a0e2c63adbb0
parent	8635c18e4091bd3034121ca98439bf40bce72324

stage2 LLVM: Use a packed aggregate for union payload init

Without the packed qualifier, the type layout that we use to
initialize doesn't match the correct layout of the underlying
storage, causing corrupted data and past-the-end writes.

3 files changed, 32 insertions(+), 2 deletions(-)

src
- codegen
  - llvm.zig
test
- behavior.zig
- behavior
  - bugs
    13128.zig

src/codegen/llvm.zig+2-2

...	...	@@ -8897,7 +8897,7 @@ pub const FuncGen = struct {
8897	8897	return union_llvm_ty.constInt(tag_int, .False);
8898	8898	}
8899	8899	assert(isByRef(union_ty));
8900		// The llvm type of the alloca will the the named LLVM union type, which will not
	8900	// The llvm type of the alloca will be the named LLVM union type, and will not
8901	8901	// necessarily match the format that we need, depending on which tag is active. We
8902	8902	// must construct the correct unnamed struct type here and bitcast, in order to
8903	8903	// then set the fields appropriately.
...	...	@@ -8922,7 +8922,7 @@ pub const FuncGen = struct {
8922	8922	const fields: [2]*llvm.Type = .{
8923	8923	field_llvm_ty, self.context.intType(8).arrayType(padding_len),
8924	8924	};
8925		break :p self.context.structType(&fields, fields.len, .False);
	8925	break :p self.context.structType(&fields, fields.len, .True);
8926	8926	};
8927	8927	if (layout.tag_size == 0) {
8928	8928	const fields: [1]*llvm.Type = .{payload};

test/behavior.zig+1

...	...	@@ -100,6 +100,7 @@ test {
100	100	_ = @import("behavior/bugs/12928.zig");
101	101	_ = @import("behavior/bugs/12945.zig");
102	102	_ = @import("behavior/bugs/12984.zig");
	103	_ = @import("behavior/bugs/13128.zig");
103	104	_ = @import("behavior/byteswap.zig");
104	105	_ = @import("behavior/byval_arg_var.zig");
105	106	_ = @import("behavior/call.zig");

test/behavior/bugs/13128.zig created+29

...	...	@@ -0,0 +1,29 @@
	1	const std = @import("std");
	2	const builtin = @import("builtin");
	3	const expect = std.testing.expect;
	4
	5	const U = union(enum) {
	6	x: u128,
	7	y: [17]u8,
	8	};
	9
	10	fn foo(val: U) !void {
	11	try expect(val.x == 1);
	12	}
	13
	14	test "runtime union init, most-aligned field != largest" {
	15	if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
	16	if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
	17	if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
	18	if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
	19	if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
	20
	21	var x: u8 = 1;
	22	try foo(.{ .x = x });
	23
	24	const val: U = @unionInit(U, "x", x);
	25	try expect(val.x == 1);
	26
	27	const val2: U = .{ .x = x };
	28	try expect(val2.x == 1);
	29	}