Support @[Link]'s DLL search order in the interpreter on Windows

spec/compiler/ffi/ffi_spec.cr

@@ -19,6 +19,22 @@ private record TestStruct,
   d : Float64,
   p : Pointer(Void)
 
+private def dll_search_paths
+  {% if flag?(:msvc) %}
+    [SPEC_CRYSTAL_LOADER_LIB_PATH]
+  {% else %}
+    nil
+  {% end %}
+end
+
+{% if flag?(:unix) %}
+  class Crystal::Loader
+    def self.new(search_paths : Array(String), *, dll_search_paths : Nil)
+      new(search_paths)
+    end
+  end
+{% end %}
+
 describe Crystal::FFI::CallInterface do
   before_all do
     FileUtils.mkdir_p(SPEC_CRYSTAL_LOADER_LIB_PATH)
@@ -33,7 +49,7 @@ describe Crystal::FFI::CallInterface do
     it "simple call" do
       call_interface = Crystal::FFI::CallInterface.new Crystal::FFI::Type.sint64, [] of Crystal::FFI::Type
 
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
       loader.load_library "sum"
       function_pointer = loader.find_symbol("answer")
       return_value = 0_i64
@@ -48,7 +64,7 @@ describe Crystal::FFI::CallInterface do
         Crystal::FFI::Type.sint32, Crystal::FFI::Type.sint32, Crystal::FFI::Type.sint32,
       ] of Crystal::FFI::Type
 
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
       loader.load_library "sum"
       function_pointer = loader.find_symbol("sum")
 
@@ -71,7 +87,7 @@ describe Crystal::FFI::CallInterface do
         Crystal::FFI::Type.pointer,
       ] of Crystal::FFI::Type
 
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
       loader.load_library "sum"
       function_pointer = loader.find_symbol("sum_primitive_types")
 
@@ -109,7 +125,7 @@ describe Crystal::FFI::CallInterface do
       ]
       call_interface = Crystal::FFI::CallInterface.new Crystal::FFI::Type.struct(struct_fields), struct_fields
 
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
       loader.load_library "sum"
       function_pointer = loader.find_symbol("make_struct")
 
@@ -145,7 +161,7 @@ describe Crystal::FFI::CallInterface do
         ]),
       ] of Crystal::FFI::Type
 
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
       loader.load_library "sum"
       function_pointer = loader.find_symbol("sum_struct")
 
@@ -183,7 +199,7 @@ describe Crystal::FFI::CallInterface do
           ]),
         ] of Crystal::FFI::Type
 
-        loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+        loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
         loader.load_library "sum"
         function_pointer = loader.find_symbol("sum_array")
 
@@ -208,7 +224,7 @@ describe Crystal::FFI::CallInterface do
     it "basic" do
       call_interface = Crystal::FFI::CallInterface.variadic Crystal::FFI::Type.sint64, [Crystal::FFI::Type.sint32, Crystal::FFI::Type.sint32, Crystal::FFI::Type.sint32, Crystal::FFI::Type.sint32] of Crystal::FFI::Type, 1
 
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
       loader.load_library "sum"
       function_pointer = loader.find_symbol("sum_variadic")
 
@@ -224,7 +240,7 @@ describe Crystal::FFI::CallInterface do
     it "zero varargs" do
       call_interface = Crystal::FFI::CallInterface.variadic Crystal::FFI::Type.sint64, [Crystal::FFI::Type.sint32] of Crystal::FFI::Type, 1
 
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH])
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: dll_search_paths)
       loader.load_library "sum"
       function_pointer = loader.find_symbol("sum_variadic")
 

spec/compiler/loader/msvc_spec.cr

@@ -45,7 +45,7 @@ describe Crystal::Loader do
 
     describe "#load_file?" do
       it "finds function symbol" do
-        loader = Crystal::Loader.new([] of String)
+        loader = Crystal::Loader.new([] of String, dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         loader.load_file?(File.join(SPEC_CRYSTAL_LOADER_LIB_PATH, Crystal::Loader.library_filename("foo"))).should be_true
         loader.find_symbol?("foo").should_not be_nil
       ensure
@@ -55,15 +55,15 @@ describe Crystal::Loader do
 
     describe "#load_library?" do
       it "library name" do
-        loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+        loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         loader.load_library?("foo").should be_true
         loader.find_symbol?("foo").should_not be_nil
       ensure
         loader.close_all if loader
       end
 
       it "full path" do
-        loader = Crystal::Loader.new([] of String)
+        loader = Crystal::Loader.new([] of String, dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         loader.load_library?(File.join(SPEC_CRYSTAL_LOADER_LIB_PATH, Crystal::Loader.library_filename("foo"))).should be_true
         loader.find_symbol?("foo").should_not be_nil
       ensure
@@ -72,7 +72,7 @@ describe Crystal::Loader do
 
       it "does not implicitly find dependencies" do
         build_c_dynlib(compiler_datapath("loader", "bar.c"))
-        loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+        loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         loader.load_library?("bar").should be_true
         loader.find_symbol?("bar").should_not be_nil
         loader.find_symbol?("foo").should be_nil
@@ -83,23 +83,23 @@ describe Crystal::Loader do
       it "lookup in order" do
         build_c_dynlib(compiler_datapath("loader", "foo2.c"))
 
-        help_loader1 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+        help_loader1 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         help_loader1.load_library?("foo").should be_true
         foo_address = help_loader1.find_symbol?("foo").should_not be_nil
 
-        help_loader2 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+        help_loader2 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         help_loader2.load_library?("foo2").should be_true
         foo2_address = help_loader2.find_symbol?("foo").should_not be_nil
 
         foo_address.should_not eq foo2_address
 
-        loader1 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+        loader1 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         loader1.load_library("foo")
         loader1.load_library("foo2")
 
         loader1.find_symbol?("foo").should eq foo_address
 
-        loader2 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+        loader2 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
         loader2.load_library("foo2")
         loader2.load_library("foo")
 
@@ -114,18 +114,59 @@ describe Crystal::Loader do
     end
 
     it "does not find global symbols" do
-      loader = Crystal::Loader.new([] of String)
+      loader = Crystal::Loader.new([] of String, dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
       loader.find_symbol?("__crystal_main").should be_nil
     end
 
     it "validate that lib handles are properly closed" do
-      loader = Crystal::Loader.new([] of String)
+      loader = Crystal::Loader.new([] of String, dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
       expect_raises(Crystal::Loader::LoadError, "undefined reference to `foo'") do
         loader.find_symbol("foo")
       end
     end
   end
 
+  describe "dll_search_paths" do
+    it "supports an arbitrary path different from lib search path" do
+      with_tempfile("loader-dll_search_paths") do |path|
+        FileUtils.mkdir_p(SPEC_CRYSTAL_LOADER_LIB_PATH)
+        FileUtils.mkdir_p(path)
+
+        build_c_dynlib(compiler_datapath("loader", "foo.c"))
+        File.rename(File.join(SPEC_CRYSTAL_LOADER_LIB_PATH, "foo.dll"), File.join(path, "foo.dll"))
+
+        loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String, dll_search_paths: [path])
+        loader.load_library?("foo").should be_true
+      ensure
+        loader.try &.close_all
+
+        FileUtils.rm_rf(path)
+        FileUtils.rm_rf(SPEC_CRYSTAL_LOADER_LIB_PATH)
+      end
+    end
+
+    it "doesn't load DLLs outside dll_search_path or Windows' default search paths" do
+      with_tempfile("loader-dll_search_paths") do |path|
+        FileUtils.mkdir_p(SPEC_CRYSTAL_LOADER_LIB_PATH)
+        FileUtils.mkdir_p(path)
+
+        build_c_dynlib(compiler_datapath("loader", "foo.c"))
+        File.rename(File.join(SPEC_CRYSTAL_LOADER_LIB_PATH, "foo.dll"), File.join(path, "foo.dll"))
+
+        loader1 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String, dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
+        loader1.load_library?("foo").should be_false
+        loader2 = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+        loader2.load_library?("foo").should be_false
+      ensure
+        loader2.try &.close_all
+        loader1.try &.close_all
+
+        FileUtils.rm_rf(path)
+        FileUtils.rm_rf(SPEC_CRYSTAL_LOADER_LIB_PATH)
+      end
+    end
+  end
+
   describe "lib suffix" do
     before_all do
       FileUtils.mkdir_p(SPEC_CRYSTAL_LOADER_LIB_PATH)
@@ -137,15 +178,15 @@ describe Crystal::Loader do
 
     it "respects -dynamic" do
       build_c_dynlib(compiler_datapath("loader", "foo.c"), lib_name: "foo-dynamic")
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
       loader.load_library?("foo").should be_true
     ensure
       loader.close_all if loader
     end
 
     it "ignores -static" do
       build_c_dynlib(compiler_datapath("loader", "foo.c"), lib_name: "bar-static")
-      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH] of String)
+      loader = Crystal::Loader.new([SPEC_CRYSTAL_LOADER_LIB_PATH], dll_search_paths: [SPEC_CRYSTAL_LOADER_LIB_PATH])
       loader.load_library?("bar").should be_false
     ensure
       loader.close_all if loader

src/compiler/crystal/codegen/link.cr

@@ -232,6 +232,10 @@ module Crystal
       flags.join(" ")
     end
 
+    # Searches among CRYSTAL_LIBRARY_PATH, the compiler's directory, and PATH
+    # for every DLL specified in the used `@[Link]` annotations. Yields the
+    # absolute path and `true` if found, the base name and `false` if not found.
+    # The directories should match `Crystal::Repl::Context#dll_search_paths`
     def each_dll_path(& : String, Bool ->)
       executable_path = nil
       compiler_origin = nil

src/compiler/crystal/interpreter/context.cr

@@ -409,7 +409,7 @@ class Crystal::Repl::Context
     # (MSVC doesn't seem to have this issue)
     args.delete("-lgc")
 
-    Crystal::Loader.parse(args).tap do |loader|
+    Crystal::Loader.parse(args, dll_search_paths: dll_search_paths).tap do |loader|
       # FIXME: Part 2: This is a workaround for initial integration of the interpreter:
       # We append a handle to the current executable (i.e. the compiler program)
       # to the loader's handle list. This gives the loader access to all the symbols in the compiler program,
@@ -427,6 +427,27 @@ class Crystal::Repl::Context
     end
   }
 
+  # Extra DLL search paths to mimic compiled code's DLL-copying behavior
+  # regarding `@[Link]` annotations. These directories should match the ones
+  # used in `Crystal::Program#each_dll_path`
+  private def dll_search_paths
+    {% if flag?(:msvc) %}
+      paths = CrystalLibraryPath.paths
+
+      if executable_path = Process.executable_path
+        paths << File.dirname(executable_path)
+      end
+
+      ENV["PATH"]?.try &.split(Process::PATH_DELIMITER, remove_empty: true) do |path|
+        paths << path
+      end
+
+      paths
+    {% else %}
+      nil
+    {% end %}
+  end
+
   def c_function(name : String)
     loader.find_symbol(name)
   end

src/compiler/crystal/loader.cr

@@ -14,6 +14,7 @@ class Crystal::Loader
   class LoadError < Exception
     property args : Array(String)?
     property search_paths : Array(String)?
+    property dll_search_paths : Array(String)?
 
     def message
       String.build do |io|
@@ -26,28 +27,26 @@ class Crystal::Loader
           io << "\nSearch path: "
           search_paths.join(io, Process::PATH_DELIMITER)
         end
+        if dll_search_paths = @dll_search_paths
+          io << "\nDLL search path: "
+          dll_search_paths.join(io, Process::PATH_DELIMITER)
+        end
       end
     end
   end
 
-  def self.new(search_paths : Array(String), libnames : Array(String), file_paths : Array(String)) : self
-    loader = new(search_paths)
-
+  def load_all(libnames : Array(String), file_paths : Array(String))
     file_paths.each do |path|
-      loader.load_file(::Path[path].expand)
+      load_file(::Path[path].expand)
     end
     libnames.each do |libname|
-      loader.load_library(libname)
+      load_library(libname)
     end
-    loader
   end
 
   getter search_paths : Array(String)
   getter loaded_libraries = [] of String
-
-  def initialize(@search_paths : Array(String))
-    @handles = [] of Handle
-  end
+  @handles = [] of Handle
 
   # def self.library_filename(libname : String) : String
   #   raise NotImplementedError.new("library_filename")