Compiler Explorer

C++ for cortex m0+ flags:

	-mthumb -mcpu=cortex-m0plus -mfloat-abi=soft

Other falgs:

	-O3 -Wall -Wextra -Wpedantic -Wshadow

ffunction-sections, -fdata-sections, & --gc-sections

-fno-exceptions

-O3 -Wall -Wextra -Wpedantic -Wshadow -mthumb -mcpu=cortex-m0plus -mfloat-abi=soft -fdata-sections -ffunction-sections -fno-exceptions -fno-rtti

Exception handling and RTTI are difficult to provide without dynamic memory allocation (much more on that below), so you likely want to disable them with fno-exceptions, fno-non-call-exceptions, and fno-rtti.