LibJS: Add minimum changes to build on Windows and run js.exe

This commit adds the minimal export macros needed to run js.exe on
windows. A followup commit is planned to move to explicit export
entirely.

A static_assert for the size of a struct is also ifdef'ed out as the
semantics around object layout and inheritance are different on MSVC abi
and the struct IteratorRecord ends up being 40 bytes not 32.

Libraries/LibJS/Bytecode/Interpreter.cpp

@@ -16,6 +16,7 @@
 #include <LibJS/Bytecode/Interpreter.h>
 #include <LibJS/Bytecode/Label.h>
 #include <LibJS/Bytecode/Op.h>
+#include <LibJS/Export.h>
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Accessor.h>
 #include <LibJS/Runtime/Array.h>
@@ -1789,7 +1790,7 @@ inline ThrowCompletionOr<Value> delete_by_value_with_this(Bytecode::Interpreter&
     return Value(TRY(reference.delete_(vm)));
 }
 
-class PropertyNameIterator final
+class JS_API PropertyNameIterator final
     : public Object
     , public BuiltinIterator {
     JS_OBJECT(PropertyNameIterator, Object);

Libraries/LibJS/Bytecode/Interpreter.h

@@ -104,7 +104,7 @@ private:
     ExecutionContext* m_running_execution_context { nullptr };
 };
 
-extern bool g_dump_bytecode;
+JS_API extern bool g_dump_bytecode;
 
 ThrowCompletionOr<GC::Ref<Bytecode::Executable>> compile(VM&, ASTNode const&, JS::FunctionKind kind, FlyString const& name);
 ThrowCompletionOr<GC::Ref<Bytecode::Executable>> compile(VM&, ECMAScriptFunctionObject const&);

Libraries/LibJS/CMakeLists.txt

@@ -290,3 +290,7 @@ else()
 endif()
 
 target_link_libraries(LibJS PUBLIC JSClangPlugin)
+
+# TODO: Use lagom_generate_export_header and annotate entire LibJS with export macros
+include(GenerateExportHeader)
+generate_export_header(LibJS EXPORT_MACRO_NAME JS_API EXPORT_FILE_NAME "Export.h")

Libraries/LibJS/Contrib/Test262/GlobalObject.h

@@ -7,11 +7,12 @@
 #pragma once
 
 #include <LibJS/Contrib/Test262/262Object.h>
+#include <LibJS/Export.h>
 #include <LibJS/Runtime/GlobalObject.h>
 
 namespace JS::Test262 {
 
-class GlobalObject final : public JS::GlobalObject {
+class JS_API GlobalObject final : public JS::GlobalObject {
     JS_OBJECT(GlobalObject, JS::GlobalObject);
     GC_DECLARE_ALLOCATOR(GlobalObject);
 

Libraries/LibJS/Runtime/ErrorTypes.h

@@ -8,6 +8,7 @@
 
 #include <AK/String.h>
 #include <AK/StringView.h>
+#include <LibJS/Export.h>
 
 #define JS_ENUMERATE_ERROR_TYPES(M)                                                                                                 \
     M(AccessorBadField, "Accessor descriptor's '{}' field must be a function or undefined")                                         \
@@ -306,7 +307,7 @@
 
 namespace JS {
 
-class ErrorType {
+class JS_API ErrorType {
 public:
 #define __ENUMERATE_JS_ERROR(name, message) \
     static const ErrorType name;

Libraries/LibJS/Runtime/Iterator.h

@@ -37,7 +37,10 @@ private:
     virtual void visit_edges(Cell::Visitor&) override;
 };
 
+// msvc abi semantics about layout with inheritance differ from Sys-V
+#if !defined(AK_OS_WINDOWS)
 static_assert(sizeof(IteratorRecord) == 32);
+#endif
 
 class Iterator : public Object {
     JS_OBJECT(Iterator, Object);