fix: defer calling napi_module_register() until weak node api injection

Early implementation just to get the app running. Without this change, the application crashes immediately after process was created.

This is triggered by dynamic linker load addons at start up, and the "twisted addon" has a function decorated with `__attribute__ ((constructor))` which calls `napi_module_register()` before even Weak NodeAPI has change to inject the proper function pointers...

Author: Mariusz Pasinski

packages/host/scripts/generate-weak-node-api-injector.ts

@@ -42,6 +42,7 @@ export function generateSource(functions: FunctionDecl[]) {
 
     log_debug("Injecting WeakNodeApiHost");
     inject_weak_node_api_host(WeakNodeApiHost {
+      .napi_module_register = napi_module_register,
       ${functions
         .filter(({ kind }) => kind === "engine")
         .flatMap(({ name }) => `.${name} = ${name},`)

packages/host/scripts/generate-weak-node-api.ts

@@ -33,17 +33,43 @@ export function generateHeader(functions: FunctionDecl[]) {
  * Generates source code for a version script for the given Node API version.
  */
 export function generateSource(functions: FunctionDecl[]) {
+  const interceptModuleRegisterCalls = true;
   return [
     "// This file is generated by react-native-node-api",
+    `#define WITH_DEFERRED_NAPI_MODULE_REGISTER ${interceptModuleRegisterCalls ? 1 : 0}`,
     `#include "weak_node_api.hpp"`, // Generated header
+    "",
+    // Declare globals needed for bookkeeping intercepted calls
+    "#if WITH_DEFERRED_NAPI_MODULE_REGISTER",
+    "#include <mutex>",
+    "#include <vector>",
+    "std::mutex g_internal_state_mutex;",
+    "std::vector<napi_module*> g_pending_modules;",
+    "#endif // WITH_DEFERRED_NAPI_MODULE_REGISTER",
+    "",
     // Generate the struct of function pointers
     "WeakNodeApiHost g_host;",
     "void inject_weak_node_api_host(const WeakNodeApiHost& host) {",
     "  g_host = host;",
+    "",
+    "#if WITH_DEFERRED_NAPI_MODULE_REGISTER",
+    "  // Flush pending `napi_module_register()` calls",
+    "  if (nullptr != host.napi_module_register) {",
+    "    std::lock_guard<std::mutex> lock(g_internal_state_mutex);",
+    "    fprintf(stderr,",
+    `      "Flushing %zu intercepted calls to 'napi_module_register'...\\n",`,
+    "      g_pending_modules.size());",
+    "    for (napi_module *module : g_pending_modules) {",
+    "      host.napi_module_register(module);",
+    "    }",
+    "    g_pending_modules.clear();",
+    "  }",
+    "#endif // WITH_DEFERRED_NAPI_MODULE_REGISTER",
     "};",
-    ``,
+    "",
     // Generate function calling into the host
     ...functions.flatMap(({ returnType, noReturn, name, argumentTypes }) => {
+      const isDeferrable = name === "napi_module_register";
       return [
         `extern "C" ${returnType} ${
           noReturn ? " __attribute__((noreturn))" : ""
@@ -52,14 +78,26 @@ export function generateSource(functions: FunctionDecl[]) {
           .join(", ")}) {`,
         `if (g_host.${name} == nullptr) {`,
         `  fprintf(stderr, "Node-API function '${name}' called before it was injected!\\n");`,
-        "  abort();",
-        "}",
-        (returnType === "void" ? "" : "return ") +
+        ...(isDeferrable ? [
+          "#if WITH_DEFERRED_NAPI_MODULE_REGISTER",
+          "  {",
+          "    std::lock_guard<std::mutex> guard(g_internal_state_mutex);",
+          "    g_pending_modules.push_back(arg0);",
+          "  }",
+          "#else",
+          "  abort();",
+          "#endif // WITH_DEFERRED_NAPI_MODULE_REGISTER",
+        ] : [
+          "  abort();",
+        ]),
+        "} else {",
+        "  " + (returnType === "void" ? "" : "return ") +
           "g_host." +
           name +
           "(" +
           argumentTypes.map((_, index) => `arg${index}`).join(", ") +
           ");",
+        "}",
         "};",
       ];
     }),