Have things finally working with switch input and LED outputs.
Issue was due to messed up SRAM define in linker script. IDK what datasheet I was reading.. But I had the location and size completely wrong. That caused any access of SRAM to cause a hardfault of course. First happening when popping anything to the stack. Which also explains why I couldn't look at the stack to figure out the last called instruciton to point to where the issue was... copied stm32f0xx_*.h files over from STM32F0xx_StdPeriph_Driver/inc dir
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