Revert "Sema: Stop adding Windows implib link inputs for `extern "..."` syntax."

This reverts commit b461d07a5464aec86c533434dab0b58edfffb331.

After some discussion in the team, we've decided that this is too disruptive,
especially because the linker errors are less than helpful. That's a fixable
problem, so we might reconsider this in the future, but revert it for now.

1 files changed, 29 insertions, 10 deletions

diff --git a/src/Compilation.zig b/src/Compilation.zig
index 4024e0a49e..ae3ab118b7 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -2185,8 +2185,12 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
             .emit_docs = try options.emit_docs.resolve(arena, &options, .docs),
         };
 
-        comp.windows_libs = try std.StringArrayHashMapUnmanaged(void).init(gpa, options.windows_lib_names, &.{});
-        errdefer comp.windows_libs.deinit(gpa);
+        errdefer {
+            for (comp.windows_libs.keys()) |windows_lib| gpa.free(windows_lib);
+            comp.windows_libs.deinit(gpa);
+        }
+        try comp.windows_libs.ensureUnusedCapacity(gpa, options.windows_lib_names.len);
+        for (options.windows_lib_names) |windows_lib| comp.windows_libs.putAssumeCapacity(try gpa.dupe(u8, windows_lib), {});
 
         // Prevent some footguns by making the "any" fields of config reflect
         // the default Module settings.
@@ -2417,13 +2421,6 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
 
     if (comp.emit_bin != null and target.ofmt != .c) {
         if (!comp.skip_linker_dependencies) {
-            // These DLLs are always loaded into every Windows process.
-            if (target.os.tag == .windows and is_exe_or_dyn_lib) {
-                try comp.windows_libs.ensureUnusedCapacity(gpa, 2);
-                comp.windows_libs.putAssumeCapacity("kernel32", {});
-                comp.windows_libs.putAssumeCapacity("ntdll", {});
-            }
-
             // If we need to build libc for the target, add work items for it.
             // We go through the work queue so that building can be done in parallel.
             // If linking against host libc installation, instead queue up jobs
@@ -2512,7 +2509,7 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
 
                     // When linking mingw-w64 there are some import libs we always need.
                     try comp.windows_libs.ensureUnusedCapacity(gpa, mingw.always_link_libs.len);
-                    for (mingw.always_link_libs) |name| comp.windows_libs.putAssumeCapacity(name, {});
+                    for (mingw.always_link_libs) |name| comp.windows_libs.putAssumeCapacity(try gpa.dupe(u8, name), {});
                 } else {
                     return error.LibCUnavailable;
                 }
@@ -2610,6 +2607,7 @@ pub fn destroy(comp: *Compilation) void {
     comp.c_object_work_queue.deinit();
     comp.win32_resource_work_queue.deinit();
 
+    for (comp.windows_libs.keys()) |windows_lib| gpa.free(windows_lib);
     comp.windows_libs.deinit(gpa);
 
     {
@@ -7795,6 +7793,27 @@ fn getCrtPathsInner(
     };
 }
 
+pub fn addLinkLib(comp: *Compilation, lib_name: []const u8) !void {
+    // Avoid deadlocking on building import libs such as kernel32.lib
+    // This can happen when the user uses `build-exe foo.obj -lkernel32` and
+    // then when we create a sub-Compilation for zig libc, it also tries to
+    // build kernel32.lib.
+    if (comp.skip_linker_dependencies) return;
+    const target = &comp.root_mod.resolved_target.result;
+    if (target.os.tag != .windows or target.ofmt == .c) return;
+
+    // This happens when an `extern "foo"` function is referenced.
+    // If we haven't seen this library yet and we're targeting Windows, we need
+    // to queue up a work item to produce the DLL import library for this.
+    const gop = try comp.windows_libs.getOrPut(comp.gpa, lib_name);
+    if (gop.found_existing) return;
+    {
+        errdefer _ = comp.windows_libs.pop();
+        gop.key_ptr.* = try comp.gpa.dupe(u8, lib_name);
+    }
+    try comp.queueJob(.{ .windows_import_lib = gop.index });
+}
+
 /// This decides the optimization mode for all zig-provided libraries, including
 /// compiler-rt, libcxx, libc, libunwind, etc.
 pub fn compilerRtOptMode(comp: Compilation) std.builtin.OptimizeMode {