From f8c9cf8fd98439e7f39a34f45a3d9998aa3d8d7c Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw2@infradead.org>
Date: Tue, 16 Dec 2025 22:37:58 +0000
Subject: [PATCH] Use PROGMEM for version text sensor strings on ESP8266

Build version string incrementally from PROGMEM literals using
ESPHOME_strncpy_P and ESPHOME_strncat_P. Write hash and build time
directly into buffer without temporary variables. Calculate buffer
size based on actual components needed.

Add ESPHOME_strncat_P macro to progmem.h for cross-platform PROGMEM
string concatenation.
---
 .../version/version_text_sensor.cpp           | 27 +++++++++----------
 esphome/core/progmem.h                        |  2 ++
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/esphome/components/version/version_text_sensor.cpp b/esphome/components/version/version_text_sensor.cpp
index 33ff35f0019..56df4e96bb7 100644
--- a/esphome/components/version/version_text_sensor.cpp
+++ b/esphome/components/version/version_text_sensor.cpp
@@ -3,6 +3,7 @@
 #include "esphome/core/log.h"
 #include "esphome/core/version.h"
 #include "esphome/core/helpers.h"
+#include "esphome/core/progmem.h"
 
 namespace esphome {
 namespace version {
@@ -11,26 +12,24 @@ static const char *const TAG = "version.text_sensor";
 
 void VersionTextSensor::setup() {
   static const char PREFIX[] PROGMEM = ESPHOME_VERSION " (config hash 0x";
-  char version_str[128];
+  static const char BUILT_STR[] PROGMEM = ", built ";
+  // Buffer size: PREFIX + 8 hex chars + BUILT_STR + BUILD_TIME_STR_SIZE + ")" + null
+  constexpr size_t BUF_SIZE = sizeof(PREFIX) + 8 + sizeof(BUILT_STR) + esphome::Application::BUILD_TIME_STR_SIZE + 2;
+  char version_str[BUF_SIZE];
 
-#ifdef USE_ESP8266
-  strcpy_P(version_str, PREFIX);
-#else
-  strcpy(version_str, PREFIX);
-#endif
+  ESPHOME_strncpy_P(version_str, PREFIX, sizeof(version_str));
 
-  char hash_str[9];
-  snprintf(hash_str, sizeof(hash_str), "%08" PRIx32, App.get_config_hash());
-  strcat(version_str, hash_str);
+  size_t len = strlen(version_str);
+  snprintf(version_str + len, sizeof(version_str) - len, "%08" PRIx32, App.get_config_hash());
 
   if (!this->hide_timestamp_) {
-    strcat(version_str, ", built: ");
-    char build_time_str[esphome::Application::BUILD_TIME_STR_SIZE];
-    App.get_build_time_string(build_time_str);
-    strcat(version_str, build_time_str);
+    size_t len = strlen(version_str);
+    ESPHOME_strncat_P(version_str, BUILT_STR, sizeof(version_str) - len - 1);
+    ESPHOME_strncat_P(version_str, ESPHOME_BUILD_TIME_STR, sizeof(version_str) - strlen(version_str) - 1);
   }
 
-  strcat(version_str, ")");
+  strncat(version_str, ")", sizeof(version_str) - strlen(version_str) - 1);
+  version_str[sizeof(version_str) - 1] = '\0';
   this->publish_state(version_str);
 }
 float VersionTextSensor::get_setup_priority() const { return setup_priority::DATA; }
diff --git a/esphome/core/progmem.h b/esphome/core/progmem.h
index f9508945e87..d1594f47e73 100644
--- a/esphome/core/progmem.h
+++ b/esphome/core/progmem.h
@@ -9,8 +9,10 @@
 #define ESPHOME_F(string_literal) F(string_literal)
 #define ESPHOME_PGM_P PGM_P
 #define ESPHOME_strncpy_P strncpy_P
+#define ESPHOME_strncat_P strncat_P
 #else
 #define ESPHOME_F(string_literal) (string_literal)
 #define ESPHOME_PGM_P const char *
 #define ESPHOME_strncpy_P strncpy
+#define ESPHOME_strncat_P strncat
 #endif