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Value: implement writeToMemory for packed unions

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Matt Knight 2023-02-18 14:10:27 -05:00 committed by GitHub
parent c993af6234
commit 07630eb696
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2 changed files with 37 additions and 0 deletions
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19
src/value.zig
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@ -1340,6 +1340,14 @@ pub const Value = extern union {
const int = mod.global_error_set.get(val.castTag(.@"error").?.data.name).?;
std.mem.writeInt(Int, buffer[0..@sizeOf(Int)], @intCast(Int, int), endian);
},
.Union => switch (ty.containerLayout()) {
.Auto => unreachable,
.Extern => @panic("TODO implement writeToMemory for extern unions"),
.Packed => {
const byte_count = (@intCast(usize, ty.bitSize(target)) + 7) / 8;
writeToPackedMemory(val, ty, mod, buffer[0..byte_count], 0);
},
},
else => @panic("TODO implement writeToMemory for more types"),
}
}
@ -1430,6 +1438,17 @@ pub const Value = extern union {
}
},
},
.Union => switch (ty.containerLayout()) {
.Auto => unreachable, // Sema is supposed to have emitted a compile error already
.Extern => unreachable, // Handled in non-packed writeToMemory
.Packed => {
const field_index = ty.unionTagFieldIndex(val.unionTag(), mod);
const field_type = ty.unionFields().values()[field_index.?].ty;
const field_val = val.fieldValue(field_type, field_index.?);
field_val.writeToPackedMemory(field_type, mod, buffer, bit_offset);
},
},
else => @panic("TODO implement writeToPackedMemory for more types"),
}
}

18
test/behavior/comptime_memory.zig
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@ -394,3 +394,21 @@ test "accessing reinterpreted memory of parent object" {
try testing.expect(b == expected);
}
}
test "bitcast packed union to integer" {
const U = packed union {
x: u1,
y: u2,
};
comptime {
const a = U{ .x = 1 };
const b = U{ .y = 2 };
const cast_a = @bitCast(u2, a);
const cast_b = @bitCast(u2, b);
// truncated because the upper bit is garbage memory that we don't care about
try testing.expectEqual(@as(u1, 1), @truncate(u1, cast_a));
try testing.expectEqual(@as(u2, 2), cast_b);
}
}