From 0eb6876aed38547c59554bd289b050d6098b290b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Mon, 19 Jan 2026 23:09:56 +0100
Subject: [PATCH] compiler: fix and simplify DllMainCRTStartup handling

See: https://github.com/llvm/llvm-project/pull/171680
---
 lib/std/start.zig    |  7 ++++---
 src/codegen/llvm.zig |  1 +
 src/link/Lld.zig     | 12 +-----------
 3 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/lib/std/start.zig b/lib/std/start.zig
index 9bc001fe59..6d748ba202 100644
--- a/lib/std/start.zig
+++ b/lib/std/start.zig
@@ -20,8 +20,9 @@ comptime {
     _ = root;
 
     if (builtin.output_mode == .Lib and builtin.link_mode == .dynamic) {
-        if (native_os == .windows and !@hasDecl(root, "_DllMainCRTStartup")) {
-            @export(&_DllMainCRTStartup, .{ .name = "_DllMainCRTStartup" });
+        const dll_main_crt_startup = if (builtin.abi.isGnu()) "DllMainCRTStartup" else "_DllMainCRTStartup";
+        if (native_os == .windows and !@hasDecl(root, dll_main_crt_startup)) {
+            @export(&DllMainCRTStartup, .{ .name = dll_main_crt_startup });
         }
     } else if (builtin.output_mode == .Exe or @hasDecl(root, "main")) {
         if (builtin.link_libc and @hasDecl(root, "main")) {
@@ -71,7 +72,7 @@ comptime {
     }
 }
 
-fn _DllMainCRTStartup(
+fn DllMainCRTStartup(
     hinstDLL: std.os.windows.HINSTANCE,
     fdwReason: std.os.windows.DWORD,
     lpReserved: std.os.windows.LPVOID,
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index b9a53360fe..d694291bb9 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -1648,6 +1648,7 @@ pub const Object = struct {
                 if (name.eqlSlice("WinMainCRTStartup", ip)) flags.winmain_crt_startup = true;
                 if (name.eqlSlice("wWinMainCRTStartup", ip)) flags.wwinmain_crt_startup = true;
                 if (name.eqlSlice("DllMainCRTStartup", ip)) flags.dllmain_crt_startup = true;
+                if (name.eqlSlice("_DllMainCRTStartup", ip)) flags.dllmain_crt_startup = true;
             }
         }
 
diff --git a/src/link/Lld.zig b/src/link/Lld.zig
index a63793d36a..19fae5c868 100644
--- a/src/link/Lld.zig
+++ b/src/link/Lld.zig
@@ -637,17 +637,7 @@ fn coffLink(lld: *Lld, arena: Allocator) !void {
                             try argv.append("-ALTERNATENAME:__image_base__=__ImageBase");
                         }
 
-                        if (is_dyn_lib) {
-                            try argv.append(try comp.crtFileAsString(arena, "dllcrt2.obj"));
-                            if (target.cpu.arch == .x86) {
-                                try argv.append("-ALTERNATENAME:__DllMainCRTStartup@12=_DllMainCRTStartup@12");
-                            } else {
-                                try argv.append("-ALTERNATENAME:_DllMainCRTStartup=DllMainCRTStartup");
-                            }
-                        } else {
-                            try argv.append(try comp.crtFileAsString(arena, "crt2.obj"));
-                        }
-
+                        try argv.append(try comp.crtFileAsString(arena, if (is_dyn_lib) "dllcrt2.obj" else "crt2.obj"));
                         try argv.append(try comp.crtFileAsString(arena, "libmingw32.lib"));
                     } else {
                         try argv.append(switch (comp.config.link_mode) {