zig

commit bfd2cc5a3fb05fb45496df544a1f075606aac270 (tree)
parent 097ca369d57a816512b726423ca97e07875a20c8
Author: Hila Friedman <red.black.liquorice@gmail.com>
Date:   Tue, 17 Mar 2026 02:10:27 +0100

even tighter return type for `std.math.sign` (#31485)

The code in #31475 does not return the "smallest integer type that fits possible values" for very small integer types, namely `u0`, `i0`, and `i1` - which all end up with a return type one bit too long. Fixed in this commit.

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31485
Reviewed-by: Andrew Kelley <andrew@ziglang.org>
Co-authored-by: Hila Friedman <red.black.liquorice@gmail.com>
Co-committed-by: Hila Friedman <red.black.liquorice@gmail.com>

Diffstat:
M
lib/std/math.zig
 | 
17
+++++------------

1 file changed, 5 insertions(+), 12 deletions(-)
diff --git a/lib/std/math.zig b/lib/std/math.zig
@@ -1775,10 +1775,7 @@ pub const F80 = struct {
 fn SignOf(T: type) type {
     return switch (@typeInfo(T)) {
         .comptime_int, .comptime_float => comptime_int,
-        .int => |int| switch (int.signedness) {
-            .signed => IntFittingRange(-1, 1),
-            .unsigned => IntFittingRange(0, 1),
-        },
+        .int => IntFittingRange(@max(minInt(T), -1), @min(maxInt(T), 1)),
         .float => IntFittingRange(-1, 1),
         .vector => |vec| @Vector(vec.len, SignOf(vec.child)),
         else => @compileError("Expected an int, float, or a vector of one, found " ++ @typeName(T)),
@@ -1792,14 +1789,10 @@ fn SignOf(T: type) type {
 /// Branchless.
 pub inline fn sign(n: anytype) SignOf(@TypeOf(n)) {
     const T = SignOf(@TypeOf(n));
-    return switch (@typeInfo(T)) {
-        .vector => |vec| blk: {
-            const zero: T = @splat(0);
-            const one: T = @splat(1);
-            break :blk @select(vec.child, n > zero, one, zero) - @select(vec.child, n < zero, one, zero);
-        },
-        else => @as(T, @intFromBool(n > 0)) - @as(T, @intFromBool(n < 0)),
-    };
+    const zero: T = if (@typeInfo(T) == .vector) @splat(0) else 0;
+    const pos: T = @intCast(@intFromBool(n > zero));
+    const neg: T = @intCast(@intFromBool(n < zero));
+    return pos - neg;
 }
 
 fn testSign() !void {