Initialization of large struct field increases binary size

[rockorager]

Zig Version

0.13.0

Steps to Reproduce and Observed Behavior

Initializing a struct with a large field results in large binary sizes, unless you manually set these fields with memset.

const std = @import("std");

const Foo = struct {
    bar: [1_000_000]u64 = undefined,
};

fn a() void {
    const foo: Foo = .{};
    _ = foo.bar;
}

fn b() void {
    var foo: Foo = undefined;
    @memset(&foo.bar, 0);
    _ = foo.bar;
}

pub fn main() !void {
    //a(); // Binary size = 10_253_888
    b(); // Binary size = 2_254_096
}

Expected Behavior

Per Andrew on IRC:

you can go ahead and file a zig bug for this because the communication to the compiler is fine, arguably zig should lower large field inits with memset rather than a big memcpy