```
$ cat overflow.zig
test {
var a: [1]u65535 = undefined;
_ = a;
}
$ zig-out/bin/zig test overflow.zig
thread 290266 panic: integer overflow
zig/src/type.zig:3604:55: 0xada43d in intAbiAlignment (zig)
std.math.ceilPowerOfTwoPromote(u16, (bits + 7) / 8),
^
zig/src/type.zig:3598:42: 0xadd4ea in intAbiSize (zig)
const alignment = intAbiAlignment(bits, target);
^
zig/src/type.zig:3500:61: 0x92be91 in abiSizeAdvanced (zig)
return AbiSizeAdvanced{ .scalar = intAbiSize(bits, target) };
^
zig/src/type.zig:3385:62: 0x928933 in abiSizeAdvanced (zig)
switch (try payload.elem_type.abiSizeAdvanced(target, strat)) {
^
zig/src/type.zig:3268:32: 0x92c012 in abiSize (zig)
return (abiSizeAdvanced(ty, target, .eager) catch unreachable).scalar;
^
```
This is only noticed in a debug build of zig and silently does the wrong
thing and overflows in release builds.
This happened to `[x]u65529` and above because of the ` + 7` on a `u16`.
Allocating an extended tag is much cleaner and easier to reason about
than reusing an existing tag. The previous `.data = undefined` was a
clear indication that we don't have any data to store, and so might as
well store an extended tag in that space almost for free.
`isAlwaysVoid` was being called with the undefined tag added by
`addOne`, causing non-deterministic behavior failures with release
builds of the compiler. Prevents the following random failure:
test/behavior/defer.zig:120:40: error: expected type 'error{One}', found 'void'
Since the owner can either be a `Decl` or a `LazySymbol` we need
to preserve this information at the codegen generate function level
so that we can then correctly work out the corresponding `Atom`
in the linker.
Pass extra pointer param with a linker ref when calling the lazy tagName
function to workaround not being able to lower linker refs during
codegen of a lazy func.
