Commit `c248af3bdc`

Andrew Kelley <andrew@ziglang.org>

2022-06-30 04:01:48

LLVM: fix lowering of untagged union types

The LLVM backend was calculating the amount of padding solely based on the payload size. However, in the case where there is no union tag, this fails to take into account alignment. Closes #11857

master

1 parent 54454fd

Changed files (3)

lib

std

net

test.zig

src

codegen

llvm.zig

test

behavior

union.zig

@@ -5,7 +5,6 @@ const mem = std.mem;
 const testing = std.testing;
 
 test "parse and render IPv6 addresses" {
-    if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest;
     if (builtin.os.tag == .wasi) return error.SkipZigTest;
 
     var buffer: [100]u8 = undefined;
@@ -68,7 +67,6 @@ test "invalid but parseable IPv6 scope ids" {
 }
 
 test "parse and render IPv4 addresses" {
-    if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest;
     if (builtin.os.tag == .wasi) return error.SkipZigTest;
 
     var buffer: [18]u8 = undefined;
@@ -93,7 +91,6 @@ test "parse and render IPv4 addresses" {
 }
 
 test "parse and render UNIX addresses" {
-    if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest;
     if (builtin.os.tag == .wasi) return error.SkipZigTest;
     if (!net.has_unix_sockets) return error.SkipZigTest;

@@ -2708,7 +2708,10 @@ pub const DeclGen = struct {
                     if (layout.most_aligned_field_size == layout.payload_size) {
                         break :t llvm_aligned_field_ty;
                     }
-                    const padding_len = @intCast(c_uint, layout.payload_size - layout.most_aligned_field_size);
+                    const padding_len = if (layout.tag_size == 0)
+                        @intCast(c_uint, layout.abi_size - layout.most_aligned_field_size)
+                    else
+                        @intCast(c_uint, layout.payload_size - layout.most_aligned_field_size);
                     const fields: [2]*const llvm.Type = .{
                         llvm_aligned_field_ty,
                         dg.context.intType(8).arrayType(padding_len),
@@ -5756,7 +5759,7 @@ pub const FuncGen = struct {
             // First set the non-null bit.
             const indices: [2]*const llvm.Value = .{
                 index_type.constNull(), // dereference the pointer
-                index_type.constInt(1, .False), // second field is the payload
+                index_type.constInt(1, .False), // second field is the non-null bit
             };
             const non_null_ptr = self.builder.buildInBoundsGEP(operand, &indices, indices.len, "");
             _ = self.builder.buildStore(non_null_bit, non_null_ptr);

@@ -1194,3 +1194,22 @@ test "union tag is set when initiated as a temporary value at runtime" {
     var b: u32 = 1;
     try (U{ .b = b }).doTheTest();
 }
+
+test "extern union most-aligned field is smaller" {
+    if (builtin.zig_backend == .stage1) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+
+    const U = extern union {
+        in6: extern struct {
+            family: u16,
+            port: u16,
+            flowinfo: u32,
+            addr: [20]u8,
+        },
+        un: [110]u8,
+    };
+    var a: ?U = .{ .un = [_]u8{0} ** 110 };
+    try expect(a != null);
+}

Commit c248af3bdc

Commit `c248af3bdc`