Commit 29717fefb8e951561bd51fdcea54ec62af3fd7dd | zig

author	Andrew Kelley <andrew@ziglang.org> 2026-10-14 15:30:56-07:00
committer	Andrew Kelley <andrew@ziglang.org> 2026-10-15 09:47:43-07:00
log	29717fefb8e951561bd51fdcea54ec62af3fd7dd
tree	356c0aec74f2c53fe12f924a79f04aea3a7401ca
parent	da32e05a1ccdeb9ede15405a599893b643ff474e

start code: flatten and improve missing pub fn main message

better error message when the programmer omits `main` or fails to make
it public.

closes #37113

1 files changed, 41 insertions(+), 35 deletions(-)

lib
- std
  - start.zig

lib/std/start.zig+41-35

...	...	@@ -29,49 +29,54 @@ comptime {
29	29	}
30	30	}
31	31	} else if (builtin.output_mode == .Exe or @hasDecl(root, "main")) {
32		if (builtin.link_libc and @hasDecl(root, "main")) {
	32	if (builtin.link_libc and (@hasDecl(root, "main") or std.os.requiresLibC())) {
33	33	if (is_wasm) {
34	34	@export(&mainWithoutEnv, .{ .name = "__main_argc_argv" });
35	35	} else if (!@typeInfo(@TypeOf(root.main)).@"fn".attrs.@"callconv".eql(.c)) {
36	36	@export(&main, .{ .name = "main" });
37	37	}
38		} else if (native_os == .windows and builtin.link_libc and @hasDecl(root, "wWinMain")) {
39		if (!@typeInfo(@TypeOf(root.wWinMain)).@"fn".attrs.@"callconv".eql(.c)) {
40		@export(&wWinMain, .{ .name = "wWinMain" });
41		}
42		} else if (native_os == .windows) {
43		if (!@hasDecl(root, "WinMain") and !@hasDecl(root, "WinMainCRTStartup") and
44		!@hasDecl(root, "wWinMain") and !@hasDecl(root, "wWinMainCRTStartup"))
45		{
46		@export(&WinStartup, .{ .name = "wWinMainCRTStartup" });
47		} else if (@hasDecl(root, "WinMain") and !@hasDecl(root, "WinMainCRTStartup") and
48		!@hasDecl(root, "wWinMain") and !@hasDecl(root, "wWinMainCRTStartup"))
49		{
50		@compileError("WinMain not supported; declare wWinMain or main instead");
51		} else if (@hasDecl(root, "wWinMain") and !@hasDecl(root, "wWinMainCRTStartup") and
52		!@hasDecl(root, "WinMain") and !@hasDecl(root, "WinMainCRTStartup"))
53		{
54		@export(&wWinMainCRTStartup, .{ .name = "wWinMainCRTStartup" });
55		}
56		} else if (native_os == .uefi) {
57		if (!@hasDecl(root, "EfiMain")) @export(&EfiMain, .{ .name = "EfiMain" });
58		} else if (native_os == .wasi) {
59		const wasm_start_sym = switch (builtin.wasi_exec_model) {
60		.reactor => "_initialize",
61		.command => "_start",
62		};
63		if (!@hasDecl(root, wasm_start_sym) and @hasDecl(root, "main")) {
	38	} else switch (native_os) {
	39	.windows => {
	40	if (builtin.link_libc and @hasDecl(root, "wWinMain")) {
	41	if (!@typeInfo(@TypeOf(root.wWinMain)).@"fn".attrs.@"callconv".eql(.c)) {
	42	@export(&wWinMain, .{ .name = "wWinMain" });
	43	}
	44	} else if (!@hasDecl(root, "WinMain") and !@hasDecl(root, "WinMainCRTStartup") and
	45	!@hasDecl(root, "wWinMain") and !@hasDecl(root, "wWinMainCRTStartup"))
	46	{
	47	@export(&WinStartup, .{ .name = "wWinMainCRTStartup" });
	48	} else if (@hasDecl(root, "WinMain") and !@hasDecl(root, "WinMainCRTStartup") and
	49	!@hasDecl(root, "wWinMain") and !@hasDecl(root, "wWinMainCRTStartup"))
	50	{
	51	@compileError("WinMain not supported; declare wWinMain or main instead");
	52	} else if (@hasDecl(root, "wWinMain") and !@hasDecl(root, "wWinMainCRTStartup") and
	53	!@hasDecl(root, "WinMain") and !@hasDecl(root, "WinMainCRTStartup"))
	54	{
	55	@export(&wWinMainCRTStartup, .{ .name = "wWinMainCRTStartup" });
	56	}
	57	},
	58
	59	.uefi => {
	60	if (!@hasDecl(root, "EfiMain")) @export(&EfiMain, .{ .name = "EfiMain" });
	61	},
	62	.wasi => {
	63	const wasm_start_sym = switch (builtin.wasi_exec_model) {
	64	.reactor => "_initialize",
	65	.command => "_start",
	66	};
	67	if (!@hasDecl(root, wasm_start_sym) and @hasDecl(root, "main")) {
	68	// Only call main when defined. For WebAssembly it's allowed to pass `-fno-entry` in which
	69	// case it's not required to provide an entrypoint such as main.
	70	@export(&startWasi, .{ .name = wasm_start_sym });
	71	}
	72	},
	73	.freestanding => if (is_wasm) {
64	74	// Only call main when defined. For WebAssembly it's allowed to pass `-fno-entry` in which
65	75	// case it's not required to provide an entrypoint such as main.
66		@export(&startWasi, .{ .name = wasm_start_sym });
67		}
68		} else if (is_wasm and native_os == .freestanding) {
69		// Only call main when defined. For WebAssembly it's allowed to pass `-fno-entry` in which
70		// case it's not required to provide an entrypoint such as main.
71		if (!@hasDecl(root, start_sym_name) and @hasDecl(root, "main")) @export(&wasm_freestanding_start, .{ .name = start_sym_name });
72		} else switch (native_os) {
	76	if (!@hasDecl(root, start_sym_name) and @hasDecl(root, "main"))
	77	@export(&wasm_freestanding_start, .{ .name = start_sym_name });
	78	},
73	79	.other,
74		.freestanding,
75	80	.vulkan,
76	81	.opengl,
77	82	.opencl,
...	...	@@ -85,6 +90,7 @@ comptime {
85	90	.psp,
86	91	.vita,
87	92	=> {},
	93
88	94	else => if (!@hasDecl(root, start_sym_name)) @export(&_start, .{ .name = start_sym_name }),
89	95	}
90	96	}