hdorio
commented
2 years ago Sorry if this is noise but I think this issue comes from += for type f80.
When doing f1 -= 0 nothing changes but doing f1 += 0 breaks f1 when f1 is of type f80 on Windows.
f64 and f128 work fine.
const builtin = @import("builtin");
const std = @import("std");
test "coerce between pointers of compatible differently-named floats" {
std.debug.print("\n", .{});
std.debug.print("stage: {d}\n", .{builtin.zig_backend});
std.debug.print("12.34: {d}\n", .{@bitCast(u80, @as(f80, 12.34))});
std.debug.print("12.34 +0: {d}\n", .{@bitCast(u80, @as(f80, 12.34) + 0)});
std.debug.print("12.34 -0: {d}\n", .{@bitCast(u80, @as(f80, 12.34) - 0)});
std.debug.print("\n", .{});
var f1: f80 = 12.34;
std.debug.print("f1 (12.34): {d}\n", .{@bitCast(u80, f1)});
f1 -= 0;
std.debug.print("f1 (12.34 -0): {d}\n", .{@bitCast(u80, f1)});
f1 += 0; // gives 302282575443171561271296
// but should be 302282575443171561271460
std.debug.print("f1 (12.34 +0): {d}\n", .{@bitCast(u80, f1)});
}
// # Windows (zig 0.10.0-dev.3475+b3d463c9e)
//PS C:\Users\user> C:\Users\user\zig\zig.exe test .\src\test\behavior\cast.zig
//Test [1/1] test "coerce between pointers of compatible differently-named floats"...
//stage: std.builtin.CompilerBackend.stage1
//12.34: 302282575443171561271460
//12.34 +0: 302282575443171561271460
//12.34 -0: 302282575443171561271460
//
//f1 (12.34): 302282575443171561271460
//f1 (12.34 -0): 302282575443171561271460
//f1 (12.34 +0): 302282575443171561271296 <--- diff
//All 1 tests passed.
// # Linux (zig 0.10.0-dev.1740+971ef7b9c)
//Test [1/1] test "coerce between pointers of compatible differently-named floats"...
//stage: std.builtin.CompilerBackend.stage1
//12.34: 302282575443171561271460
//12.34 +0: 302282575443171561271460
//12.34 -0: 302282575443171561271460
//
//f1 (12.34): 302282575443171561271460
//f1 (12.34 -0): 302282575443171561271460
//f1 (12.34 +0): 302282575443171561271460
//All 1 tests passed.
This problem has been ongoing but masked by #12380.