Commit `cd03a0a153`

Alex Rønne Petersen <alex@alexrp.com>

2025-06-02 19:02:08

compiler: Don't link ucrtbased.dll when targeting *-windows-msvc in Debug mode.

Linking it by default means that we produce binaries that, effectively, only run on systems which have the Windows SDK installed because ucrtbased.dll is not redistributable, and the Windows SDK is what actually installs ucrtbased.dll into %SYSTEM32%. The resulting binaries also can't run under Wine because Wine does not provide ucrtbased.dll. It is also inconsistent with our behavior for *-windows-gnu where we always link ucrtbase.dll. See #23983, #24019, and #24053 for more details. So just use ucrtbase.dll regardless of mode. With this change, we can also drop the implicit definition of the _DEBUG macro in zig cc, which has in some cases been problematic for users. Users who want to opt into the old behavior can do so, both for *-windows-msvc and *-windows-gnu, by explicitly passing -lucrtbased and -D_DEBUG. We might consider adding a more ergonomic flag like -fdebug-crt to the zig build-* family of commands in the future. Closes #24052.

master

1 parent 826e1c3

Changed files (2)

src

link

Coff.zig

Compilation.zig

@@ -2113,21 +2113,17 @@ fn linkWithLLD(coff: *Coff, arena: Allocator, tid: Zcu.PerThread.Id, prog_node:
 
                         try argv.append(try comp.crtFileAsString(arena, "libmingw32.lib"));
                     } else {
+                        try argv.append(switch (comp.config.link_mode) {
+                            .static => "libcmt.lib",
+                            .dynamic => "msvcrt.lib",
+                        });
+
                         const lib_str = switch (comp.config.link_mode) {
-                            .dynamic => "",
                             .static => "lib",
+                            .dynamic => "",
                         };
-                        const d_str = switch (optimize_mode) {
-                            .Debug => "d",
-                            else => "",
-                        };
-                        switch (comp.config.link_mode) {
-                            .static => try argv.append(try allocPrint(arena, "libcmt{s}.lib", .{d_str})),
-                            .dynamic => try argv.append(try allocPrint(arena, "msvcrt{s}.lib", .{d_str})),
-                        }
-
-                        try argv.append(try allocPrint(arena, "{s}vcruntime{s}.lib", .{ lib_str, d_str }));
-                        try argv.append(try allocPrint(arena, "{s}ucrt{s}.lib", .{ lib_str, d_str }));
+                        try argv.append(try allocPrint(arena, "{s}vcruntime.lib", .{lib_str}));
+                        try argv.append(try allocPrint(arena, "{s}ucrt.lib", .{lib_str}));
 
                         //Visual C++ 2015 Conformance Changes
                         //https://msdn.microsoft.com/en-us/library/bb531344.aspx

@@ -5904,8 +5904,7 @@ fn updateWin32Resource(comp: *Compilation, win32_resource: *Win32Resource, win32
         // them being defined matches the behavior of how MSVC calls rc.exe which is the more
         // relevant behavior in this case.
         switch (rc_src.owner.optimize_mode) {
-            .Debug => try argv.append("-D_DEBUG"),
-            .ReleaseSafe => {},
+            .Debug, .ReleaseSafe => {},
             .ReleaseFast, .ReleaseSmall => try argv.append("-DNDEBUG"),
         }
         try argv.appendSlice(rc_src.extra_flags);
@@ -6260,10 +6259,7 @@ pub fn addCCArgs(
         // LLVM IR files don't support these flags.
         if (ext != .ll and ext != .bc) {
             switch (mod.optimize_mode) {
-                .Debug => {
-                    // windows c runtime requires -D_DEBUG if using debug libraries
-                    try argv.append("-D_DEBUG");
-                },
+                .Debug => {},
                 .ReleaseSafe => {
                     try argv.append("-D_FORTIFY_SOURCE=2");
                 },

Commit cd03a0a153

Commit `cd03a0a153`