Save PROGMEM on serial prefixes (#12033)

With default config and `EEPROM_SETTINGS`, saves over 200 bytes of PROGMEM.

Marlin/src/HAL/HAL_LPC1768/HAL.cpp

@@ -75,13 +75,13 @@ void HAL_adc_init(void) {
 #include "../../core/language.h"
 
 extern void kill(PGM_P);
-extern const char errormagic[];
 
 void HAL_adc_enable_channel(int ch) {
   pin_t pin = analogInputToDigitalPin(ch);
 
   if (pin == -1) {
-    SERIAL_PRINTF("%sINVALID ANALOG PORT:%d\n", errormagic, ch);
+    serial_error_start();
+    SERIAL_PRINTF("INVALID ANALOG PORT:%d\n", ch);
     kill(MSG_KILLED);
   }
 

Marlin/src/core/serial.cpp

@@ -42,6 +42,10 @@ const char echomagic[] PROGMEM = "echo:";
   void serial_echopair_PGM_P(const int8_t p, PGM_P s_P, unsigned long v) { serialprintPGM_P(p, s_P); SERIAL_ECHO_P(p, v); }
 
   void serial_spaces_P(const int8_t p, uint8_t count) { count *= (PROPORTIONAL_FONT_RATIO); while (count--) SERIAL_CHAR_P(p, ' '); }
+
+  void serial_echo_start_P(const int8_t p)  { serialprintPGM_P(p, echomagic); }
+  void serial_error_start_P(const int8_t p) { serialprintPGM_P(p, errormagic); }
+
 #endif
 
 void serialprintPGM(PGM_P str) {
@@ -59,6 +63,9 @@ void serial_echopair_PGM(PGM_P s_P, unsigned long v) { serialprintPGM(s_P); SERI
 
 void serial_spaces(uint8_t count) { count *= (PROPORTIONAL_FONT_RATIO); while (count--) SERIAL_CHAR(' '); }
 
+void serial_echo_start()  { serialprintPGM(echomagic); }
+void serial_error_start() { serialprintPGM(errormagic); }
+
 #if ENABLED(DEBUG_LEVELING_FEATURE)
 
   #include "enum.h"

Marlin/src/core/serial.h

@@ -44,9 +44,6 @@ enum DebugFlags : unsigned char {
 extern uint8_t marlin_debug_flags;
 #define DEBUGGING(F) (marlin_debug_flags & (DEBUG_## F))
 
-extern const char echomagic[] PROGMEM;
-extern const char errormagic[] PROGMEM;
-
 #if TX_BUFFER_SIZE < 1
   #define SERIAL_FLUSHTX_P(p)
   #define SERIAL_FLUSHTX()
@@ -84,7 +81,7 @@ extern const char errormagic[] PROGMEM;
   #define SERIAL_PROTOCOLPAIR_P(p, pre, value)      (serial_echopair_PGM_P(p,PSTR(pre),(value)))
   #define SERIAL_PROTOCOLLNPAIR_P(p, pre, value)    do{ SERIAL_PROTOCOLPAIR_P(p, pre, value); SERIAL_EOL_P(p); }while(0)
 
-  #define SERIAL_ECHO_START_P(p)             (serialprintPGM_P(p,echomagic))
+  #define SERIAL_ECHO_START_P(p)                    serial_echo_start_P(p)
   #define SERIAL_ECHO_P(p,x)                        SERIAL_PROTOCOL_P(p,x)
   #define SERIAL_ECHOPGM_P(p,x)                     SERIAL_PROTOCOLPGM_P(p,x)
   #define SERIAL_ECHOLN_P(p,x)                      SERIAL_PROTOCOLLN_P(p,x)
@@ -93,7 +90,7 @@ extern const char errormagic[] PROGMEM;
   #define SERIAL_ECHOLNPAIR_P(p,pre, value)         SERIAL_PROTOCOLLNPAIR_P(p, pre, value)
   #define SERIAL_ECHO_F_P(p,x,y)                    SERIAL_PROTOCOL_F_P(p,x,y)
 
-  #define SERIAL_ERROR_START_P(p)            (serialprintPGM_P(p,errormagic))
+  #define SERIAL_ERROR_START_P(p)                   serial_error_start_P(p)
   #define SERIAL_ERROR_P(p,x)                       SERIAL_PROTOCOL_P(p,x)
   #define SERIAL_ERRORPGM_P(p,x)                    SERIAL_PROTOCOLPGM_P(p,x)
   #define SERIAL_ERRORLN_P(p,x)                     SERIAL_PROTOCOLLN_P(p,x)
@@ -123,7 +120,11 @@ extern const char errormagic[] PROGMEM;
   #define SERIAL_PROTOCOL_SP_P(p,C)                 serial_spaces_P(p,C)
 
   void serialprintPGM_P(const int8_t p, PGM_P str);
-#else
+  void serial_echo_start_P(const int8_t p);
+  void serial_error_start_P(const int8_t p);
+
+#else // NUM_SERIAL < 2
+
   #define SERIAL_CHAR_P(p,x)                        SERIAL_CHAR(x)
   #define SERIAL_PROTOCOL_P(p,x)                    SERIAL_PROTOCOL(x)
   #define SERIAL_PROTOCOL_F_P(p,x,y)                SERIAL_PROTOCOL_F(x,y)
@@ -184,7 +185,8 @@ extern const char errormagic[] PROGMEM;
   #define SERIAL_PROTOCOL_SP_P(p,C)                 SERIAL_PROTOCOL_SP(C)
 
   #define serialprintPGM_P(p,s)                     serialprintPGM(s)
-#endif
+
+#endif // NUM_SERIAL < 2
 
 #define SERIAL_EOL() SERIAL_CHAR('\n')
 
@@ -194,7 +196,7 @@ extern const char errormagic[] PROGMEM;
 #define SERIAL_PROTOCOLPAIR(pre, value)             (serial_echopair_PGM(PSTR(pre), value))
 #define SERIAL_PROTOCOLLNPAIR(pre, value)           do { SERIAL_PROTOCOLPAIR(pre, value); SERIAL_EOL(); } while(0)
 
-#define SERIAL_ECHO_START()            (serialprintPGM(echomagic))
+#define SERIAL_ECHO_START()                         serial_echo_start()
 #define SERIAL_ECHO(x)                              SERIAL_PROTOCOL(x)
 #define SERIAL_ECHOPGM(x)                           SERIAL_PROTOCOLPGM(x)
 #define SERIAL_ECHOLN(x)                            SERIAL_PROTOCOLLN(x)
@@ -203,7 +205,7 @@ extern const char errormagic[] PROGMEM;
 #define SERIAL_ECHOLNPAIR(pre, value)               SERIAL_PROTOCOLLNPAIR(pre, value)
 #define SERIAL_ECHO_F(x,y)                          SERIAL_PROTOCOL_F(x, y)
 
-#define SERIAL_ERROR_START()           (serialprintPGM(errormagic))
+#define SERIAL_ERROR_START()                        serial_error_start()
 #define SERIAL_ERROR(x)                             SERIAL_PROTOCOL(x)
 #define SERIAL_ERRORPGM(x)                          SERIAL_PROTOCOLPGM(x)
 #define SERIAL_ERRORLN(x)                           SERIAL_PROTOCOLLN(x)
@@ -236,6 +238,8 @@ void serial_spaces(uint8_t count);
 // Functions for serial printing from PROGMEM. (Saves loads of SRAM.)
 //
 void serialprintPGM(PGM_P str);
+void serial_echo_start();
+void serial_error_start();
 
 #if ENABLED(DEBUG_LEVELING_FEATURE)
   void print_xyz(PGM_P prefix, PGM_P suffix, const float x, const float y, const float z);