Currently, grammar.y is out of sync with the actual grammar implemented by the zig compiler (in std/zig/tokenizer and std/zig/parser.zig).
These are the places where grammar.y and zig diverges, found with the improved parser from https://github.com/ziglang/zig-spec/pull/42, using files in src and lib/std in the zig repository.
-
doc-comments not allowed in top-level
comptimeandtestdeclaration./// doc-comment for comptime.comptime{vara=1;_=a;}/// doc-comment for test.test{} -
Saturating arithmetic is not supported by
grammar.y.test{vara:isize=10;a+|=1;a-|=1;a*|=1;a<<|=1;constb:isize=a+|1;constc:isize=b-|1;constd:isize=c*|1;conste:isize=d<<|1;_=e;} -
Mixed
doc-commentandline-commentis not supported bygrammar.y.// A doc-comment followed by a line-comment is not supported by grammar.y.constS=struct{//! doc/// doc// doca:i32,};NOTE: I found mixing
doc-commentandline-commentconfusing, andautodocdoesn't not handle them correctly.Examples:
-
std/mem.zig:3760
/// Force an evaluation of the expression; this tries to prevent/// the compiler from optimizing the computation away even if the/// result eventually gets discarded.// TODO: use @declareSideEffect() when it is available - https://github.com/ziglang/zig/issues/6168pubfndoNotOptimizeAway(val:anytype)void{See: https://ziglang.org/documentation/master/std/#root;mem.doNotOptimizeAway.
-
std/coff.zig:354
/// This relocation is meaningful only when the machine type is ARM or Thumb./// The base relocation applies the 32-bit address of a symbol across a consecutive MOVW/MOVT instruction pair.// ARM_MOV32 = 5,/// This relocation is only meaningful when the machine type is RISC-V./// The base relocation applies to the high 20 bits of a 32-bit absolute address.// RISCV_HIGH20 = 5,/// Reserved, must be zero.RESERVED=6,See https://ziglang.org/documentation/master/std/#root;coff.BaseRelocationType.
-
-
New
addrspacekeyword.Commit: ziglang/zig@ccc7f9987 (Address spaces: addrspace(A) parsing)
Date: 2021年09月14日test { const y: *allowzero align(8) addrspace(.generic) const volatile u32 = undefined; _ = y; } -
Inline switch prong not supported by
grammar.y.Commit: ziglang/zig@b4d81857f (stage1+2: parse inline switch cases)
Date: 2022年02月13日conststd=@import("std");constexpect=std.testing.expect;constSliceTypeA=externstruct{len:usize,ptr:[*]u32,};constSliceTypeB=externstruct{ptr:[*]SliceTypeA,len:usize,};constAnySlice=union(enum){a:SliceTypeA,b:SliceTypeB,c:[]constu8,d:[]AnySlice,};fnwithSwitch(any:AnySlice)usize{returnswitch(any){// With `inline else` the function is explicitly generated// as the desired switch and the compiler can check that// every possible case is handled.inlineelse=>|slice|slice.len,};}test"inline else"{varany=AnySlice{.c="hello"};tryexpect(withSwitch(any)==5);} -
New packed
structsyntax.Commit: ziglang/zig@6249a24e8 (stage2: integer-backed packed structs)
Date: 2022年02月23日pubconstAbsolutePointerModeAttributes=packedstruct(u32){supports_alt_active:bool,supports_pressure_as_z:bool,_pad:u30=0,};
Currently, `grammar.y` is out of sync with the actual grammar implemented by the `zig` compiler (in `std/zig/tokenizer` and `std/zig/parser.zig`).
These are the places where `grammar.y` and `zig` diverges, found with the improved parser from https://github.com/ziglang/zig-spec/pull/42, using files in `src` and `lib/std` in the `zig` repository.
- [ ] doc-comments not allowed in top-level `comptime` and `test` declaration.
```zig
/// doc-comment for comptime.
comptime {
var a = 1;
_ = a;
}
/// doc-comment for test.
test {}
```
- [ ] Saturating arithmetic is not supported by `grammar.y`.
```zig
test {
var a: isize = 10;
a +|= 1;
a -|= 1;
a *|= 1;
a <<|= 1;
const b: isize = a +| 1;
const c: isize = b -| 1;
const d: isize = c *| 1;
const e: isize = d <<| 1;
_ = e;
}
```
- [ ] Mixed `doc-comment` and `line-comment` is not supported by `grammar.y`.
```zig
// A doc-comment followed by a line-comment is not supported by grammar.y.
const S = struct {
//! doc
/// doc
// doc
a: i32,
};
```
**NOTE**: I found mixing `doc-comment` and `line-comment` confusing, and `autodoc` doesn't not handle them correctly.
Examples:
- std/mem.zig:3760
```zig
/// Force an evaluation of the expression; this tries to prevent
/// the compiler from optimizing the computation away even if the
/// result eventually gets discarded.
// TODO: use @declareSideEffect() when it is available - https://github.com/ziglang/zig/issues/6168
pub fn doNotOptimizeAway(val: anytype) void {
```
See: https://ziglang.org/documentation/master/std/#root;mem.doNotOptimizeAway.
- std/coff.zig:354
```zig
/// This relocation is meaningful only when the machine type is ARM or Thumb.
/// The base relocation applies the 32-bit address of a symbol across a consecutive MOVW/MOVT instruction pair.
// ARM_MOV32 = 5,
/// This relocation is only meaningful when the machine type is RISC-V.
/// The base relocation applies to the high 20 bits of a 32-bit absolute address.
// RISCV_HIGH20 = 5,
/// Reserved, must be zero.
RESERVED = 6,
```
See https://ziglang.org/documentation/master/std/#root;coff.BaseRelocationType.
- [ ] New `addrspace` keyword.
Commit: ziglang/zig@ccc7f9987 (Address spaces: addrspace(A) parsing)
Date: 2021年09月14日
```
test {
const y: *allowzero align(8) addrspace(.generic) const volatile u32 = undefined;
_ = y;
}
```
- [ ] Inline switch prong not supported by `grammar.y`.
Commit: ziglang/zig@b4d81857f (stage1+2: parse inline switch cases)
Date: 2022年02月13日
```zig
const std = @import("std");
const expect = std.testing.expect;
const SliceTypeA = extern struct {
len: usize,
ptr: [*]u32,
};
const SliceTypeB = extern struct {
ptr: [*]SliceTypeA,
len: usize,
};
const AnySlice = union(enum) {
a: SliceTypeA,
b: SliceTypeB,
c: []const u8,
d: []AnySlice,
};
fn withSwitch(any: AnySlice) usize {
return switch (any) {
// With `inline else` the function is explicitly generated
// as the desired switch and the compiler can check that
// every possible case is handled.
inline else => |slice| slice.len,
};
}
test "inline else" {
var any = AnySlice{ .c = "hello" };
try expect(withSwitch(any) == 5);
}
```
- [ ] New packed `struct` syntax.
Commit: ziglang/zig@6249a24e8 (stage2: integer-backed packed structs)
Date: 2022年02月23日
```zig
pub const AbsolutePointerModeAttributes = packed struct(u32) {
supports_alt_active: bool,
supports_pressure_as_z: bool,
_pad: u30 = 0,
};
```