From 9eae0cd2534c69f4fd470670b2b943e700939ee3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kuba=20Szczodrzy=C5=84ski?= <kuba@szczodrzynski.pl>
Date: Sun, 1 Jun 2025 19:38:11 +0200
Subject: [PATCH] [common] Add Arduino emptyString declaration

---
 builder/utils/cores.py                            | 2 +-
 cores/common/arduino/src/wiring/wiring_compat.cpp | 3 +++
 cores/common/arduino/src/wiring/wiring_compat.h   | 1 +
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/builder/utils/cores.py b/builder/utils/cores.py
index 9e40184..e9fd32c 100644
--- a/builder/utils/cores.py
+++ b/builder/utils/cores.py
@@ -51,7 +51,7 @@ def env_add_core_sources(env: Environment, queue, name: str, path: str) -> bool:
             "+<compat/*.c*>",
             "+<port/*.c*>",
             "+<posix/*.c>",
-            "+<wiring/*.c>",
+            "+<wiring/*.c*>",
             "+<wraps/*.c>",
         ],
         includes=[
diff --git a/cores/common/arduino/src/wiring/wiring_compat.cpp b/cores/common/arduino/src/wiring/wiring_compat.cpp
index 72549b3..88eae5f 100644
--- a/cores/common/arduino/src/wiring/wiring_compat.cpp
+++ b/cores/common/arduino/src/wiring/wiring_compat.cpp
@@ -7,3 +7,6 @@ String ipToString(const IPAddress &ip) {
 	sprintf(szRet, "%hhu.%hhu.%hhu.%hhu", ip[0], ip[1], ip[2], ip[3]);
 	return String(szRet);
 }
+
+// global empty string to allow returning const String& with nothing
+const String emptyString;
diff --git a/cores/common/arduino/src/wiring/wiring_compat.h b/cores/common/arduino/src/wiring/wiring_compat.h
index 00ffb03..2c9be66 100644
--- a/cores/common/arduino/src/wiring/wiring_compat.h
+++ b/cores/common/arduino/src/wiring/wiring_compat.h
@@ -35,6 +35,7 @@ extern "C" {
 
 #ifdef __cplusplus
 String ipToString(const IPAddress &ip);
+extern const String emptyString;
 #endif
 
 #ifdef __cplusplus