warning: 'prog_char' is deprecated: prog_char type is deprecated

Using Arduino Programming Questions
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arduino-1.8.12 32-bit on Raspbian Buster10:

Although this is just a warning:

/opt/arduino/hardware/tools/avr/bin/avr-g++ -MMD -c -D__PROG_TYPES_COMPAT__ -mmcu=atmega2560 -DF_CPU=16000000L -DARDUINO=1812 -DARDUINO_ARCH_AVR -I/opt/arduino/hardware/arduino/avr/cores/arduino -I/opt/arduino/hardware/arduino/avr/cores/arduino/api -I/opt/arduino/hardware/arduino/avr/variants/mega     -I/home/somuser/sketchbook/libraries/AccelStepper/src -Wall -ffunction-sections -fdata-sections -Os -fpermissive -fno-exceptions -std=gnu++11 -fno-threadsafe-statics -flto -fno-devirtualize -fdiagnostics-color=always /opt/arduino/hardware/arduino/avr/cores/arduino/Print.cpp -o build-mega-atmega2560/core/Print.cpp.o
/opt/arduino/hardware/arduino/avr/cores/arduino/Print.cpp: In member function 'size_t Print::print(const __FlashStringHelper*)':
/opt/arduino/hardware/arduino/avr/cores/arduino/Print.cpp:46:9: warning: 'prog_char' is deprecated: prog_char type is deprecated. [-Wdeprecated-declarations]
   PGM_P p = reinterpret_cast<PGM_P>(ifsh);
         ^
In file included from /opt/arduino/hardware/arduino/avr/cores/arduino/Arduino.h:28:0,
                 from /opt/arduino/hardware/arduino/avr/cores/arduino/Print.cpp:27:
/opt/arduino-1.8.12/hardware/tools/avr/avr/include/avr/pgmspace.h:354:14: note: declared here
 typedef char prog_char __attribute__((__progmem__,deprecated("prog_char type is deprecated.")));
              ^~~~~~~~~

I would prefer having warning free compilings. My code only uses 1 single external library the AccelStepper. I think this is some issue in the core.

Can you please make this warning go away in 1.8.13 in the future if it's not relevant? I could not even find any reference to prog_char in any of my code or libraries.

Thanks

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My best guess is the error is in line 113. Of course, if you'd prefer a better answer than just a guess, read the first three posts to this Forum and then post your code using Code Tags.

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The deprecated definitions seem to be used (in avr/pgmspace.h) when the identifier DOXYGEN is not defined. I don't know what would cause that. I wrote a short sketch using the F() macro and it compiled without error or warning for an Arduino UNO on 1.8.12.

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