zig

commit e6ebdcb82ed9fd226ef18670115b8b2617c0a392 (tree)
parent 8635c18e4091bd3034121ca98439bf40bce72324
Author: Cody Tapscott <topolarity@tapscott.me>
Date:   Mon, 10 Oct 2022 23:57:48 -0700

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.

Diffstat:
M
src/codegen/llvm.zig
 | 
4
++--
M
test/behavior.zig
 | 
1
+
A
test/behavior/bugs/13128.zig
 | 
29
+++++++++++++++++++++++++++++

3 files changed, 32 insertions(+), 2 deletions(-)
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
@@ -8897,7 +8897,7 @@ pub const FuncGen = struct {
             return union_llvm_ty.constInt(tag_int, .False);
         }
         assert(isByRef(union_ty));
-        // The llvm type of the alloca will the the named LLVM union type, which will not
+        // The llvm type of the alloca will be the named LLVM union type, and will not
         // necessarily match the format that we need, depending on which tag is active. We
         // must construct the correct unnamed struct type here and bitcast, in order to
         // then set the fields appropriately.
@@ -8922,7 +8922,7 @@ pub const FuncGen = struct {
                 const fields: [2]*llvm.Type = .{
                     field_llvm_ty, self.context.intType(8).arrayType(padding_len),
                 };
-                break :p self.context.structType(&fields, fields.len, .False);
+                break :p self.context.structType(&fields, fields.len, .True);
             };
             if (layout.tag_size == 0) {
                 const fields: [1]*llvm.Type = .{payload};
diff --git a/test/behavior.zig b/test/behavior.zig
@@ -100,6 +100,7 @@ test {
     _ = @import("behavior/bugs/12928.zig");
     _ = @import("behavior/bugs/12945.zig");
     _ = @import("behavior/bugs/12984.zig");
+    _ = @import("behavior/bugs/13128.zig");
     _ = @import("behavior/byteswap.zig");
     _ = @import("behavior/byval_arg_var.zig");
     _ = @import("behavior/call.zig");
diff --git a/test/behavior/bugs/13128.zig b/test/behavior/bugs/13128.zig
@@ -0,0 +1,29 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const expect = std.testing.expect;
+
+const U = union(enum) {
+    x: u128,
+    y: [17]u8,
+};
+
+fn foo(val: U) !void {
+    try expect(val.x == 1);
+}
+
+test "runtime union init, most-aligned field != largest" {
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+
+    var x: u8 = 1;
+    try foo(.{ .x = x });
+
+    const val: U = @unionInit(U, "x", x);
+    try expect(val.x == 1);
+
+    const val2: U = .{ .x = x };
+    try expect(val2.x == 1);
+}