Miscompilation in cortex-m-rt 0.7.1 and 0.7.2
Version 0.7.1 of the cortex-m-rt crate introduced a regression causing the stack to NOT be eight-byte aligned prior to calling main (or any other specified entrypoint), violating the [stack ABI of AAPCS32], the default ABI used by all Cortex-M targets. This regression is also present in version 0.7.2 of the cortex-m-rt crate. This regression can cause certain compiler optimizations (which assume the eight-byte alignment) to produce incorrect behavior at runtime. …