[ci] Soft-deprecate str_sprintf/str_snprintf to prevent hidden heap allocations

esphome/components/tormatic/tormatic_protocol.h

@@ -55,7 +55,6 @@ enum MessageType : uint16_t {
   COMMAND = 0x0106,
 };
 
-// Max string length: 7 ("Unknown"/"Command"). Update print() buffer sizes if adding longer strings.
 inline const char *message_type_to_str(MessageType t) {
   switch (t) {
     case STATUS:
@@ -84,11 +83,7 @@ struct MessageHeader {
   }
 
   std::string print() {
-    // 64 bytes: "MessageHeader: seq " + uint16 + ", len " + uint32 + ", type " + type + safety margin
-    char buf[64];
-    snprintf(buf, sizeof(buf), "MessageHeader: seq %d, len %d, type %s", this->seq, this->len,
-             message_type_to_str(this->type));
-    return buf;
+    return str_sprintf("MessageHeader: seq %d, len %d, type %s", this->seq, this->len, message_type_to_str(this->type));
   }
 
   void byteswap() {
@@ -136,7 +131,6 @@ inline CoverOperation gate_status_to_cover_operation(GateStatus s) {
   return COVER_OPERATION_IDLE;
 }
 
-// Max string length: 11 ("Ventilating"). Update print() buffer sizes if adding longer strings.
 inline const char *gate_status_to_str(GateStatus s) {
   switch (s) {
     case PAUSED:
@@ -176,12 +170,7 @@ struct StatusReply {
   GateStatus state;
   uint8_t trailer = 0x0;
 
-  std::string print() {
-    // 48 bytes: "StatusReply: state " (19) + state (11) + safety margin
-    char buf[48];
-    snprintf(buf, sizeof(buf), "StatusReply: state %s", gate_status_to_str(this->state));
-    return buf;
-  }
+  std::string print() { return str_sprintf("StatusReply: state %s", gate_status_to_str(this->state)); }
 
   void byteswap(){};
 } __attribute__((packed));
@@ -213,12 +202,7 @@ struct CommandRequestReply {
   CommandRequestReply() = default;
   CommandRequestReply(GateStatus state) { this->state = state; }
 
-  std::string print() {
-    // 56 bytes: "CommandRequestReply: state " (27) + state (11) + safety margin
-    char buf[56];
-    snprintf(buf, sizeof(buf), "CommandRequestReply: state %s", gate_status_to_str(this->state));
-    return buf;
-  }
+  std::string print() { return str_sprintf("CommandRequestReply: state %s", gate_status_to_str(this->state)); }
 
   void byteswap() { this->type = convert_big_endian(this->type); }
 } __attribute__((packed));

esphome/core/helpers.h

@@ -563,9 +563,11 @@ inline uint32_t fnv1_hash_object_id(const char *str, size_t len) {
 }
 
 /// snprintf-like function returning std::string of maximum length \p len (excluding null terminator).
+/// @warning Allocates heap memory. Use snprintf() with a stack buffer instead.
 std::string __attribute__((format(printf, 1, 3))) str_snprintf(const char *fmt, size_t len, ...);
 
 /// sprintf-like function returning std::string.
+/// @warning Allocates heap memory. Use snprintf() with a stack buffer instead.
 std::string __attribute__((format(printf, 1, 2))) str_sprintf(const char *fmt, ...);
 
 /// Concatenate a name with a separator and suffix using an efficient stack-based approach.

script/ci-custom.py

@@ -690,6 +690,8 @@ HEAP_ALLOCATING_HELPERS = {
     "str_truncate": "removal (function is unused)",
     "str_upper_case": "removal (function is unused)",
     "str_snake_case": "removal (function is unused)",
+    "str_sprintf": "snprintf() with a stack buffer",
+    "str_snprintf": "snprintf() with a stack buffer",
 }
 
 
@@ -706,7 +708,9 @@ HEAP_ALLOCATING_HELPERS = {
     r"get_mac_address(?!_)|"
     r"str_truncate|"
     r"str_upper_case|"
-    r"str_snake_case"
+    r"str_snake_case|"
+    r"str_sprintf|"
+    r"str_snprintf"
     r")\s*\(" + CPP_RE_EOL,
     include=cpp_include,
     exclude=[