Hello,
I have observed this issue in version 6.16.1 across several MCU series (F3, F4, H5, H7), though it appears likely that all earlier versions are affected.
The generated .cmake toolchain files incorrectly treat the --specs=nano.specs option as linker-only. This option should be applied globally, as it also affects the system include paths used during compilation. Specifically, it causes the compiler to include arm-none-eabi/include/newlib-nano/newlib.h instead of the standard arm-none-eabi/include/newlib.h.
While this mismatch probably does not break ABI compatibility—since the structures provided from the standard headers are larger than those used in the compiled newlib-nano library—it does negate the RAM usage benefits of newlib-nano. This is particularly problematic when using the USE_NEWLIB_REENTRANT FreeRTOS option.
Regards,
Peter
