cleanup: Do not return const values from functions

This generates a warning under -Wextra, since in most cases a const
value doesn't prevent buggy code (as copies are allowed) while
preventing some optimizations (such as move operations) to take place.

Firmware/mmu2_error_converter.cpp

@@ -132,24 +132,24 @@ uint16_t PrusaErrorCode(uint8_t i){
     return pgm_read_word(errorCodes + i);
 }
 
-const char * const PrusaErrorTitle(uint8_t i){
-    return (const char * const)pgm_read_ptr(errorTitles + i);
+const char * PrusaErrorTitle(uint8_t i){
+    return (const char *)pgm_read_ptr(errorTitles + i);
 }
 
-const char * const PrusaErrorDesc(uint8_t i){
-    return (const char * const)pgm_read_ptr(errorDescs + i);
+const char * PrusaErrorDesc(uint8_t i){
+    return (const char *)pgm_read_ptr(errorDescs + i);
 }
 
 uint8_t PrusaErrorButtons(uint8_t i){
     return pgm_read_byte(errorButtons + i);
 }
 
-const char * const PrusaErrorButtonTitle(uint8_t bi){
+const char * PrusaErrorButtonTitle(uint8_t bi){
     // -1 represents the hidden NoOperation button which is not drawn in any way
-    return (const char * const)pgm_read_ptr(btnOperation + bi - 1);
+    return (const char *)pgm_read_ptr(btnOperation + bi - 1);
 }
 
-const char * const PrusaErrorButtonMore(){
+const char * PrusaErrorButtonMore(){
     return _R(MSG_BTN_MORE);
 }
 

Firmware/mmu2_error_converter.h

@@ -11,11 +11,11 @@ uint8_t PrusaErrorCodeIndex(uint16_t ec);
 
 /// @returns pointer to a PROGMEM string representing the Title of the Prusa-Error-Codes error
 /// @param i index of the error - obtained by calling ErrorCodeIndex
-const char * const PrusaErrorTitle(uint8_t i);
+const char * PrusaErrorTitle(uint8_t i);
 
 /// @returns pointer to a PROGMEM string representing the multi-page Description of the Prusa-Error-Codes error
 /// @param i index of the error - obtained by calling ErrorCodeIndex
-const char * const PrusaErrorDesc(uint8_t i);
+const char * PrusaErrorDesc(uint8_t i);
 
 /// @returns the actual numerical value of the Prusa-Error-Codes error
 /// @param i index of the error - obtained by calling ErrorCodeIndex
@@ -27,10 +27,10 @@ uint8_t PrusaErrorButtons(uint8_t i);
 
 /// @returns pointer to a PROGMEM string representing the Title of a button
 /// @param i index of the error - obtained by calling PrusaErrorButtons + extracting low or high nibble from the Btns pair
-const char * const PrusaErrorButtonTitle(uint8_t bi);
+const char * PrusaErrorButtonTitle(uint8_t bi);
 
 /// @returns pointer to a PROGMEM string representing the "More" button
-const char * const PrusaErrorButtonMore();
+const char * PrusaErrorButtonMore();
 
 /// Sets the selected button for later pick-up by the MMU state machine.
 /// Used to save the GUI selection/decoupling

Firmware/mmu2_progress_converter.cpp

@@ -62,11 +62,11 @@ static const char * const progressTexts[] PROGMEM = {
     _R(MSG_PROGRESS_FEED_FSENSOR)
 };
 
-const char * const ProgressCodeToText(uint16_t pc){
+const char * ProgressCodeToText(uint16_t pc){
     // @@TODO ?? a better fallback option?
     return ( pc <= (sizeof(progressTexts) / sizeof(progressTexts[0])) )
-       ? static_cast<const char * const>(pgm_read_ptr(&progressTexts[pc]))
-       : static_cast<const char * const>(pgm_read_ptr(&progressTexts[0]));
+       ? static_cast<const char *>(pgm_read_ptr(&progressTexts[pc]))
+       : static_cast<const char *>(pgm_read_ptr(&progressTexts[0]));
 }
 
 } // namespace MMU2

Firmware/mmu2_progress_converter.h

@@ -4,6 +4,6 @@
 
 namespace MMU2 {
 
-const char * const ProgressCodeToText(uint16_t pc);
+const char * ProgressCodeToText(uint16_t pc);
 
 }

Firmware/mmu2_reporting.cpp

@@ -11,7 +11,7 @@
 
 namespace MMU2 {
 
-const char * const ProgressCodeToText(uint16_t pc); // we may join progress convertor and reporter together
+const char * ProgressCodeToText(uint16_t pc); // we may join progress convertor and reporter together
 
 void BeginReport(CommandInProgress cip, uint16_t ec) {
     custom_message_type = CustomMsg::MMUProgress;