These function attributes are supported by the RL78 back end:
interruptbrk_interruptUse brk_interrupt instead of interrupt for handlers intended to be used with the BRK opcode (i.e. those that must end with RETB instead of RETI).
nakedasm statements can safely be included in naked functions (see Basic Asm). While using extended asm or a mixture of basic asm and C code may appear to work, they cannot be depended upon to work reliably and are not supported.
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https://gcc.gnu.org/onlinedocs/gcc-6.3.0/gcc/RL78-Function-Attributes.html