From e8f28cda9edb06a5f2189ca5e8928df52ddea20d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carl=20=C3=85stholm?= <carl@astholm.se>
Date: Mon, 22 Apr 2024 22:13:49 +0200
Subject: [PATCH] std.Build: Install Windows DLLs to `<prefix>/bin/` by default

Windows does not support RPATH and only searches for DLLs in a small
number of predetermined paths by default, with one of them being the
directory from which the application loaded.

Installing both executables and DLLs to `bin/` by default helps ensure
that the executable can find any DLL artifacts it has linked to.
DLL import libraries are still installed to `lib/`.

These defaults match CMake's behavior.
---
 lib/std/Build/Step/Compile.zig         |  6 +++++-
 lib/std/Build/Step/InstallArtifact.zig | 11 ++++-------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/lib/std/Build/Step/Compile.zig b/lib/std/Build/Step/Compile.zig
index 9e94b78d6c..79bade4963 100644
--- a/lib/std/Build/Step/Compile.zig
+++ b/lib/std/Build/Step/Compile.zig
@@ -614,6 +614,10 @@ pub fn isStaticLibrary(self: *const Compile) bool {
     return self.kind == .lib and self.linkage != .dynamic;
 }
 
+pub fn isDll(self: *Compile) bool {
+    return self.isDynamicLibrary() and self.rootModuleTarget().os.tag == .windows;
+}
+
 pub fn producesPdbFile(self: *Compile) bool {
     const target = self.rootModuleTarget();
     // TODO: Is this right? Isn't PDB for *any* PE/COFF file?
@@ -632,7 +636,7 @@ pub fn producesPdbFile(self: *Compile) bool {
 }
 
 pub fn producesImplib(self: *Compile) bool {
-    return self.isDynamicLibrary() and self.rootModuleTarget().os.tag == .windows;
+    return self.isDll();
 }
 
 pub fn linkLibC(self: *Compile) void {
diff --git a/lib/std/Build/Step/InstallArtifact.zig b/lib/std/Build/Step/InstallArtifact.zig
index 7ebe8fdaf0..d9f163fce5 100644
--- a/lib/std/Build/Step/InstallArtifact.zig
+++ b/lib/std/Build/Step/InstallArtifact.zig
@@ -57,8 +57,8 @@ pub fn create(owner: *std.Build, artifact: *Step.Compile, options: Options) *Ins
         .disabled => null,
         .default => switch (artifact.kind) {
             .obj => @panic("object files have no standard installation procedure"),
-            .exe, .@"test" => InstallDir{ .bin = {} },
-            .lib => InstallDir{ .lib = {} },
+            .exe, .@"test" => .bin,
+            .lib => if (artifact.isDll()) .bin else .lib,
         },
         .override => |o| o,
     };
@@ -77,15 +77,12 @@ pub fn create(owner: *std.Build, artifact: *Step.Compile, options: Options) *Ins
         },
         .h_dir = switch (options.h_dir) {
             .disabled => null,
-            .default => switch (artifact.kind) {
-                .lib => .header,
-                else => null,
-            },
+            .default => if (artifact.kind == .lib) .header else null,
             .override => |o| o,
         },
         .implib_dir = switch (options.implib_dir) {
             .disabled => null,
-            .default => if (artifact.producesImplib()) dest_dir else null,
+            .default => if (artifact.producesImplib()) .lib else null,
             .override => |o| o,
         },