Arduino Zero: Enable RTTI

Question

I need dynamic casts for my project, I'm getting:

error: 'dynamic_cast' not permitted with -fno-rtti

It appears that RTTI (run-time type information) is disabled with the fno-rtti compiler flag.

How do I change this?

Answer 1

It apparently is true that “RTTI (run-time type information) is disabled with the fno-rtti compiler flag”; however, looking at compiler.c.flags and compiler.cpp.flags in platform.txt, no fno-rtti compiler flag is set, suggesting that gcc sets it by default.

One way to turn off fno-rtti is adding a -frtti flag into the appropriate flags string in platform.txt. As a side effect, this will affect all sketches subsequently compiled, rather than only those that need dynamic casts.

Note, on a microcontroller, a more-appropriate way to deal with the problem is getting rid of the need for dynamic casts, via function overloading.

Edit 1: On Linux, typical file paths to platform.txt are like /opt/arduino-1.6.3/hardware/arduino/avr/platform.txt or /opt/arduino-1.8.0/hardware/arduino/avr/platform.txt. I don't know the location on OSX. However, a command like locate *avr/platform.txt should reveal its location. (If locate is a new install on your system, first run updatedb, which may take a while.)