Undefined symbols in fmt with i386-uefi-msvc

[JamesLupiani]

When compiling this program:

const fmt = @import("std").fmt;

pub fn main() void {
    var buf: [100]u8 = undefined;
    var a: u64 = 42;
    _ = fmt.bufPrint(buf[0..], "{}", a) catch unreachable;
}

I get linker errors when building for UEFI 32-bit:

zig build-exe -target i386-uefi-msvc minimal.zig

lld: error: undefined symbol: __aullrem
>>> referenced by /snap/zig/966/lib/zig/std/fmt.zig:950
>>>               ./minimal.obj:(_std.fmt.formatIntUnsigned)

lld: error: undefined symbol: __aulldiv
>>> referenced by /snap/zig/966/lib/zig/std/fmt.zig:953
>>>               ./minimal.obj:(_std.fmt.formatIntUnsigned)

It does work on x86_64-uefi-msvc and i386-windows-msvc, however.

[LemonBoy]

Changing this line to if (builtin.os == .windows or builtin.os == .uefi) { should fix the problem.

[nrdmn]

Changing this line to if (builtin.os == .windows or builtin.os == .uefi) { should fix the problem.

But why would we want this code in an EFI application? Shouldn't we get llvm to not require these symbols?

[LemonBoy]

But why would we want this code in an EFI application? Shouldn't we get llvm to not require these symbols?

For the same reason you want those in a standard Win32 non-EFI application, LLVM expects those to be defined by the Microsoft compiler runtime and so makes use of them.

[andrewrk]

I wrote a tiny bit about the purpose of compiler-rt here: https://ziglang.org/download/0.5.0/release-notes.html#compiler-rt

[nrdmn]

LLVM expects those to be defined by the Microsoft compiler runtime

LLVM expects those because we're currently telling LLVM to compile EFI applications as Windows applications. See here

EDIT: Seems like we don't have much of a choice. As I understand the situation, LLVM can't generate COFF files for non-windows OSes right now.