Compiler warning when build with PIO, redefine of struct_size in main.ino

[AlmightyFrog]

It is not nice to see a warning at each fresh build, but it seems to be a wrong warning...

Describe the bug
It seems that there is something strange ongoing at converting that main.ino to main.ino.cpp giving a warning:

Verbose mode can be enabled via `-v, --verbose` option
CONFIGURATION: https://docs.platformio.org/page/boards/espressif32/esp32dev.html
PLATFORM: Espressif 32 (3.1.1) > Espressif ESP32 Dev Module
HARDWARE: ESP32 240MHz, 320KB RAM, 4MB Flash
DEBUG: Current (esp-prog) External (esp-prog, iot-bus-jtag, jlink, minimodule, olimex-arm-usb-ocd, olimex-arm-usb-ocd-h, olimex-arm-usb-tiny-h, olimex-jtag-tiny, tumpa)
PACKAGES: 
 - framework-arduinoespressif32 3.10005.210308 (1.0.5) 
 - tool-esptoolpy 1.30000.201119 (3.0.0) 
 - toolchain-xtensa32 2.50200.97 (5.2.0)
Converting main.ino
/mypath/OpenMQTTGateway-REF/main/main.ino:41:0: warning: "struct_size" redefined
 #    define struct_size 4
 ^
/mypath/OpenMQTTGateway-REF/main/main.ino:38:0: note: this is the location of the previous definition
 #    define struct_size 12
 ^

Here you can see the corresponding code after converting, which seems totally fine to me:

# if defined(ESP8266) || defined(ESP32) || defined(__AVR_ATmega2560__) || defined(__AVR_ATmega1280__)
#define struct_size 12
ReceivedSignal receivedSignal[struct_size] = {{0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}};
# else
#define struct_size 4
ReceivedSignal receivedSignal[struct_size] = {{0, 0}, {0, 0}, {0, 0}, {0, 0}};
# endif
#endif

It pretty much just removes the comments and some excessive whitespaces.

To Reproduce
Just type pio run and when it is compiling look at the output.
If you want to compare the original main.ino with the temporary main.ino.cpp just make sure to save or use it until it is remved when compile is finished.

I directly opened it with a diff tool like meld main.ino main.ino.cpp in another shell.

Environment (please complete the following information):
Latest version development.

[dkneisz]

Looks like this is more a PIO issue:
https://community.platformio.org/t/warning-symbol-redefined-probably-because-of-fpreprocessed/6362

[NorthernMan54]

This is a potential workaround

#    ifdef struct_size
#      undef struct_size
#    endif

ie

#    define struct_size 12
ReceivedSignal receivedSignal[struct_size] = {{0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}};
#  else // boards with smaller memory
#    ifdef struct_size
#      undef struct_size
#    endif
#    define struct_size 4
ReceivedSignal receivedSignal[struct_size] = {{0, 0}, {0, 0}, {0, 0}, {0, 0}};
#  endif