std.mem.Alignment is wider than it needs to be #25899
Description
Zig Version
0.15.2
Steps to Reproduce and Observed Behavior
See the minimum repro below:
// repro.zig
const std = @import("std");
fn rank(a: std.mem.Alignment) u3 {
return @intFromEnum(a);
}
pub fn main() void {
const a: std.mem.Alignment = .@"64";
const n = rank(a);
std.debug.print("{any} = {d}\n", .{ a, n });
}zig run repro.zig
repro.zig:4:12: error: expected type 'u3', found 'u6'
return @intFromEnum(a);
^~~~~~~~~~~~~~~
repro.zig:4:12: note: unsigned 3-bit int cannot represent all possible unsigned 6-bit values
repro.zig:3:31: note: function return type declared here
fn rank(a: std.mem.Alignment) u3 {Expected Behavior
std.mem.Alignment values ranges from 0 to 6. These fit in a u3 but std.mem.Alignment is backed by a u6 because of math.Log2Int(usize). This came up when building https://github.com/zig-gamedev/zemscripten with 0.15.2. The 3rd line of EmmallocAllocator.alloc fails with
error: expected type 'u5', found 'u6'