Linking with libc on Windows requires both wWinMain and WinMain

[revivalizer]

Zig Version

0.10.0-dev.95+06286b05a

Steps to Reproduce

main.zig

const win32 = @import("std").os.windows;
const WINAPI = @import("std").os.windows.WINAPI;

pub export fn wWinMain(hInstance: win32.HINSTANCE, _: ?win32.HINSTANCE, pCmdLine: [*:0]u16, nCmdShow: c_int) callconv(WINAPI) c_int {
    _ = hInstance;
    _ = nCmdShow;
    _ = pCmdLine;

    return 0;
}

build.zig

    ...
    exe.linkLibC();
    exe.single_threaded = true;    
    ...

Expected Behavior

zig build success.

Actual Behavior

λ zig build
lld-link: error: undefined symbol: WinMain
>>> referenced by mingw32.lib(crt0_c.obj):(main)
error: LLDReportedFailure
libctest...The following command exited with error code 1:
C:\Users\ralph\Downloads\zig-windows-x86_64-0.10.0-dev.95+06286b05a\zig.exe build-exe C:\code\libctest\src\main.zig -lc --cache-dir C:\code\libctest\zig-cache --global-cache-dir C:\Users\ralph\AppData\Local\zig --name libctest -fsingle-threaded --enable-cache
error: the following build command failed with exit code 1:
C:\code\libctest\zig-cache\o\9f6d466e1acf870ea83a5add8bf20452\build.exe C:\Users\ralph\Downloads\zig-windows-x86_64-0.10.0-dev.95+06286b05a\zig.exe C:\code\libctest C:\code\libctest\zig-cache C:\Users\ralph\AppData\Local\zig

Note that zig does not allow me to just use WinMain:

λ zig build
C:\Users\ralph\Downloads\zig-windows-x86_64-0.10.0-dev.95+06286b05a\lib\std\start.zig:61:21: error: WinMain not supported; declare wWinMain or main instead
                    @compileError("WinMain not supported; declare wWinMain or main instead");
                    ^
libctest...The following command exited with error code 1:
C:\Users\ralph\Downloads\zig-windows-x86_64-0.10.0-dev.95+06286b05a\zig.exe build-exe C:\code\libctest\src\main.zig -lc --cache-dir C:\code\libctest\zig-cache --global-cache-dir C:\Users\ralph\AppData\Local\zig --name libctest -fsingle-threaded --enable-cache
error: the following build command failed with exit code 1:
C:\code\libctest\zig-cache\o\9f6d466e1acf870ea83a5add8bf20452\build.exe C:\Users\ralph\Downloads\zig-windows-x86_64-0.10.0-dev.95+06286b05a\zig.exe C:\code\libctest C:\code\libctest\zig-cache C:\Users\ralph\AppData\Local\zig

Will this be fixed before you add the support for the regular WinMain? It's really not looking good, many people use external UI libraries that require us to link libC but the console subsystem makes it much worse. It would be great if this could get fixed 😄

[DarknessFX]

I got this same error just now while trying to run SDL2 without the console window, I found a way to bypass this problem:

Zig Version

0.12.0-dev.415+5af5d87ad

Steps to Reproduce

tstwnd.zig

const std = @import("std");
const win = @import("std").os.windows;

const HINSTANCE = win.HINSTANCE;
const HWND = win.HWND;

pub export fn WinMain(hInstance: HINSTANCE, hPrevInstance: ?HINSTANCE, 
  pCmdLine: [*:0]u16, nCmdShow: u32) callconv(win.WINAPI) win.INT {

    return wWinMain(hInstance, hPrevInstance, pCmdLine, nCmdShow);
}

pub export fn wWinMain(hInstance: HINSTANCE, hPrevInstance: ?HINSTANCE, 
  pCmdLine: [*:0]u16, nCmdShow: u32) callconv(win.WINAPI) win.INT {

  _ = hInstance;
  _ = hPrevInstance;
  _ = pCmdLine;
  _ = nCmdShow;

  _ = win.user32.messageBoxA(null, "Zig run -lc tstwnd.zig", "Hello Zig!", win.user32.MB_OKCANCEL) catch 0;

  return 0;
}

command
zig run -lc tstwnd.zig

Expected Behavior

A single message box popup.

This code works now but it will fail to run if compiled without libc.
zig run tstwnd.zig

error: lld-link: root: undefined symbol: _tls_index
error: lld-link: root: undefined symbol: wWinMainCRTStartup
error: lld-link: undefined symbol: _tls_index

[squeek502]

I believe this has been fixed/addressed by #19399

When using build-exe, pass -municode
When using build.zig, set exe.mingw_unicode_entry_point = true;

As a side note, you can define a normal Zig wWinMain and Zig's start code will call it with the correct parameters. Here's an example of a wWinMain function definition:

pub fn wWinMain(
    inst: std.os.windows.HINSTANCE,
    prev: ?std.os.windows.HINSTANCE,
    cmd_line: std.os.windows.LPWSTR,
    cmd_show: c_int,
) std.os.windows.INT {
    return 0;
}