Errors vs Warnings

[w9ran]

I used a library called SerialMenu to create an app that compiles and runs fine on Arduino boards. But when I try to compile for the Pico I get this error:

 passing 'const SerialMenu' as 'this' argument discards qualifiers [-fpermissive]

My understanding is that it is warning about attempting to call a non-const member function on a const instance. But I know that it works and compiles OK for Arduino so I'm thinking there is a difference in how the compiler flags are set for the two targets. (Maybe -Werror is enabled, turning warnings into errors?) The author of the library has not responded to this issue.

Is there a way to disable this error in the Arduino IDE? Or is there another explanation or fix? Thanks!

[earlephilhower]

The only -Werror we have is for missing returns because that will guarantee a crash in newer GCCs:

arduino-pico/platform.txt

Lines 46 to 50 in b506c01

	compiler.warning_flags=-Werror=return-type -Wno-psabi
	compiler.warning_flags.none=-Werror=return-type -Wno-psabi
	compiler.warning_flags.default=-Werror=return-type -Wno-psabi
	compiler.warning_flags.more=-Wall -Werror=return-type -Wno-ignored-qualifiers -Wno-psabi
	compiler.warning_flags.all=-Wall -Wextra -Werror=return-type -Wno-ignored-qualifiers -Wno-psabi -Wno-unused-parameter -Wno-missing-field-initializers

If GCC is dumping the code as an error, that's probably because it's really a C++17 problem.

You could drop the const in the object instantiation, so it's this wouldn't be const. consts live in flash and aren't copied to RAM in this architecture (but consts are in copied to RAM in other archs, like the ESP8266, where you need to use PROGMEM qualifiers to keep it out of the global RAM). On those archs even if you throw away the const and the methods change values, it will "work" (but still be a bad idea). But here it'll cause a bus error and crash the core.