src: fix --disable-single-executable-application

Previously it would not compile if the build is configured with
--disable-single-executable-application because we use directives
to exclude the definition of SEA-related code completely. This patch
changes them so that the SEA code are still compiled and internals
can still check whether the executable is an SEA. The executable would
not try to load the SEA blob at all if SEA is disabled. If future
modifications to the C++ code attempt to load the SEA blob when SEA
is disabled, UNREACHABLE() would be raised. If user attempt to
generate the SEA blob with --experimental-sea-config with an executable
that disables SEA, they would get an error.

PR-URL: nodejs#51808
Fixes: nodejs#51730
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

Author: joyeecheung

src/node.cc

@@ -1445,13 +1445,16 @@ static ExitCode StartInternal(int argc, char** argv) {
   });
 
   uv_loop_configure(uv_default_loop(), UV_METRICS_IDLE_TIME);
-
   std::string sea_config = per_process::cli_options->experimental_sea_config;
   if (!sea_config.empty()) {
+#if !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
     return sea::BuildSingleExecutableBlob(
         sea_config, result->args(), result->exec_args());
+#else
+    fprintf(stderr, "Single executable application is disabled.\n");
+    return ExitCode::kGenericUserError;
+#endif  // !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
   }
-
   // --build-snapshot indicates that we are in snapshot building mode.
   if (per_process::cli_options->per_isolate->build_snapshot) {
     if (per_process::cli_options->per_isolate->build_snapshot_config.empty() &&

src/node_sea.cc

@@ -27,8 +27,6 @@
 #include <tuple>
 #include <vector>
 
-#if !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
-
 using node::ExitCode;
 using v8::ArrayBuffer;
 using v8::BackingStore;
@@ -189,6 +187,7 @@ SeaResource SeaDeserializer::Read() {
 }
 
 std::string_view FindSingleExecutableBlob() {
+#if !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
   CHECK(IsSingleExecutable());
   static const std::string_view result = []() -> std::string_view {
     size_t size;
@@ -209,6 +208,9 @@ std::string_view FindSingleExecutableBlob() {
                      result.data(),
                      result.size());
   return result;
+#else
+  UNREACHABLE();
+#endif  // !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
 }
 
 }  // anonymous namespace
@@ -668,5 +670,3 @@ void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
 
 NODE_BINDING_CONTEXT_AWARE_INTERNAL(sea, node::sea::Initialize)
 NODE_BINDING_EXTERNAL_REFERENCE(sea, node::sea::RegisterExternalReferences)
-
-#endif  // !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)

src/node_sea.h

@@ -3,8 +3,6 @@
 
 #if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 
-#if !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
-
 #include <cinttypes>
 #include <optional>
 #include <string>
@@ -52,8 +50,6 @@ node::ExitCode BuildSingleExecutableBlob(
 }  // namespace sea
 }  // namespace node
 
-#endif  // !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
-
 #endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 
 #endif  // SRC_NODE_SEA_H_