test: debug output for dlopen-ping-pong test

Make test failures easier to diagnose through progress logging, and
reporting of dlerror().

PR-URL: #29818
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Christian Clauss <cclauss@me.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

test/addons/dlopen-ping-pong/binding.cc

@@ -26,6 +26,7 @@ static ping ping_func;
 void LoadLibrary(const FunctionCallbackInfo<Value>& args) {
   const String::Utf8Value filename(args.GetIsolate(), args[0]);
   void* handle = dlopen(*filename, RTLD_LAZY);
+  if (handle == nullptr) fprintf(stderr, "%s\n", dlerror());
   assert(handle != nullptr);
   ping_func = reinterpret_cast<ping>(dlsym(handle, "dlopen_ping"));
   assert(ping_func != nullptr);

test/addons/dlopen-ping-pong/test.js

@@ -9,12 +9,15 @@ const path = require('path');
 const os = require('os');
 
 const bindingPath = require.resolve(`./build/${common.buildType}/binding`);
+console.log('process.dlopen:', bindingPath);
 process.dlopen(module, bindingPath,
                os.constants.dlopen.RTLD_NOW | os.constants.dlopen.RTLD_GLOBAL);
+console.log('module.exports.load:', `${path.dirname(bindingPath)}/ping.so`);
 module.exports.load(`${path.dirname(bindingPath)}/ping.so`);
 assert.strictEqual(module.exports.ping(), 'pong');
 
 // Check that after the addon is loaded with
 // process.dlopen() a require() call fails.
+console.log('require:', `./build/${common.buildType}/binding`);
 const re = /^Error: Module did not self-register\.$/;
 assert.throws(() => require(`./build/${common.buildType}/binding`), re);