[Vm-beginners] mcontext_t et al

[Ken.Dickey]

Greetings,

I am grepping around to find the source of

 ..In function sqUnixMain.c: In function 'sigsegv':
include_ucontext.h:48:37: error 'mcontext_t'
  has no member 'arm_pc'

I note in 
 /usr/include/aarch64_linux_gnu/asm/sigcontext.h member 'pc' but not 'arm_pc'

I am guessing this is from the include_ucontext.h line 
  #elif __linux__ && __arm__

Where do I set/override __arm__ with (__aarch64__ or __armv8-a__ or __arm64__) ?

What is the preferred __*__ to use?

Any way to debug this cr*p?  Trace flag?  Dump defines (here)? 

Thanks much,
-KenD