This is a follow-up to PR #30053 / commit 484cc15366.
The code previously did not handle `c_longdouble`, whose size depends on
the target. A `floatSignificandBits` helper function and a smoke test
were added.
Also added the missing max int value to the exhaustive `f16` test cases.
The bugs here actually exist on master branch too, but they are being
caught by the new static assertions which check type size and alignment.
It turns out that MSVC's struct/union "pack" pragma and its "align"
declspec interact in undocumented ways which are extremely problematic
for generated code. Solving this will require changing how the C backend
lowers various types; the disabled tests are all tagged unions, but
there are also issues with structs with underaligned fields which the
behavior tests just happen to not currently be triggering.
Now that struct default value resolution is separate from struct layout
resolution, a handful of old behavior tests are now once again valid.
This partially reverts the commit titled "behavior: update for changes
to struct field default value resolution".
This is separate from the previous commit so that these changes can be
easily reverted in the event that we decide to allow more granularity in
default value resolution in exchange for increased language complexity.
Pointers to comptime-only types (e.g. `*type`) are no longer themselves
comptime-only types. This means explicit `comptime` annotations are
required in a few more places. However, it also introduces the ability
to access pointers to (including slices of) comptime-only types at
runtime, provided only runtime fields are being accessed.
`@sizeOf` and `@bitSizeOf` are now more restricted: they are not allowed
on comptime-only or NPV (uninstantiable) types. This is because there is
no correct way to actually use the returned ABI size (e.g. you cannot
copy a comptime-only type by copying all of its runtime bits), so having
a non-zero return value had no benefit and was simply confusing.
`packed struct`s and `packed union`s can no longer contain pointer
fields. There are a few reasons for this, but in particular, binary
formats do not typically support the relocation types we would need to
lower such values into static memory. See the proposal at
https://github.com/ziglang/zig/issues/24657 for details.
Unions with no fields are now "uninstantiable" types, which work like
`noreturn` in that values of this type cannot exist. Enums with no
fields are different because they are currently considered `extern`
types, though https://github.com/ziglang/zig/issues/19855 will change
this in the future.
'comptime_int' is no longer considered a valid backing type for an enum.
In other words, 'enum(comptime_int)' is a compile error. This change is
accepted to simplify the language.
e2338edb47 didn't *quite* do it, the call sites of all switch prong related
functions now have to do their part too and be a little more precise about
what kind of prong they're currently analyzing.
Also removes some unused/unnecessary stuff.
This fixes a regression from a couple of commits ago; breaking from the
`else` block of a loop to the loop's tag should be allowed when explicitly
targeting the label by name.
This commit aims to simplify and de-duplicate the logic required for
semantically analyzing `switch` expressions.
The core logic has been moved to `analyzeSwitchBlock`, `resolveSwitchBlock`
and `finishSwitchBlock` and has been rewritten around the new iterator-based
API exposed by `Zir.UnwrappedSwitchBlock`.
All validation logic and switch prong item resolution have been moved to
`validateSwitchBlock`, which produces a `ValidatedSwitchBlock` containing
all the necessary information for further analysis.
`Zir.UnwrappedSwitchBlock`, `ValidatedSwitchBlock` and `SwitchOperand`
replace `SwitchProngAnalysis` while adding more flexibility, mainly for
better integration with `switch_block_err_union`.
`analyzeSwitchBlock` has an explicit code path for OPV types which lowers
them to either a `block`-`br` or a `loop`-`repeat` construct instead of a
switch. Backends expect `switch` to actually have an operand that exists
at runtime, so this is a bug fix and avoids further special cases in the
rest of the switch logic.
`resolveSwitchBlock` and `finishSwitchBr` exclusively deal with operands
which can have more than one value, at comptime and at runtime respectively.
This commit also reworks `RangeSet` to be an unmanaged container and adds
`Air.SwitchBr.BranchHints` to offload some complexity from Sema to there
and save a few bytes of memory in the process.
Additionally, some new features have been implemented:
- decl literals and everything else requiring a result type (`@enumFromInt`!)
may now be used as switch prong items
- union tag captures are now allowed for all prongs, not just `inline` ones
- switch prongs may contain errors which are not in the error set being
switched on, if these prongs contain `=> comptime unreachable`
and some bugs have been fixed:
- lots of issues with switching on OPV types are now fixed
- the rules around unreachable `else` prongs when switching on errors now
apply to *any* switch on an error, not just to `switch_block_err_union`,
and are applied properly based on the AST
- switching on `void` no longer requires an `else` prong unconditionally
- lazy values are properly resolved before any comparisons with prong items
- evaluation order between all kinds of switch statements is now the same,
with or without label
Previously Zig allowed you to write something like,
```zig
switch (x) {
.y => |_| {
```
This seems a bit strange because in other cases, such as when
capturing the tag in a switch case,
```zig
switch (x) {
.y => |_, _| {
```
this produces an error.
The only usecase I can think of for the previous behaviour is
if you wanted to assert that all union payloads are able
to coerce,
```zig
const X = union(enum) { y: u8, z: f32 };
switch (x) {
.y, .z => |_| {
```
This will compile-error with the `|_|` and pass without it.
I don't believe this usecase is strong enough to keep the current
behaviour; it was never used in the Zig codebase and I cannot
find a single usage of this behaviour in the real world, searching
through Sourcegraph.
If the float can store all possible values of the integer without
rounding, coercion is allowed. The integer's precision must be less than
or equal to the float's significand precision.
Closes#18614
Our implementation did the classic add-sub rounding trick `(y = x +/- C =+ C - x)`
with `C = 1 / eps(T) = 2^(mantissa - 1)`. This approach only works for values whose
magnitude is below the rounding capacity of the constant. For a 64-bit mantissa
(like f80 has), `C = 2^63` only rounds for `|x| < 2^63`. Before we allowed this to
be ran on `e < bias + 64` aka `|x| < 2^64`. And because it isn't large enough,
we lose a bit to rounding.
For reference, the musl implementation does the same thing, using `mantissa - 1`:
https://git.musl-libc.org/cgit/musl/tree/src/math/ceill.c#n18
where `LDBL_MANT_DIG` is 64 for `long double` on x86.
This commit also combines the floor and ceil implementations into one generic one.
This was caused a `[0]std.builtin.Type.StructField.Attributes` to be
considered `undefined`, even though that type is OPV so should prefer
its OPV `.{}` over `undefined`.
Resolves: #30039
Apple's own headers and tbd files prefer to think of Mac Catalyst as a distinct
OS target. Earlier, when DriverKit support was added to LLVM, it was represented
a distinct OS. So why Apple decided to only represent Mac Catalyst as an ABI in
the target triple is beyond me. But this isn't the first time they've ignored
established target triple norms (see: armv7k and aarch64_32) and it probably
won't be the last.
While doing this, I also audited all Darwin OS prongs throughout the codebase
and made sure they cover all the tags.
The changes to `codegen.c` are blatant hacks, but the problem they work
around isn't a regression: it's an existing miscompilation. This branch
happened to *expose* that miscompilation in more cases by changing how
an incorrect result is *used*.
Jay Petacat