20.04 on mac M1

[Paul Smith]

On Wed, 2021-10-13 at 15:41 -0400, Jerry Geis wrote:
> Hi Paul - thanks for the reply..  So I have 
> /usr/alpha-linux-gnu/include/sys/io.h

That's odd.  It's not how the directory structure normally looks.

What does "dpkg -S /usr/alpha-linux-gnu/include/sys/io.h" tell you?

> but it must not be actually included when I compile as a standard
> include directory ???

Well, if you invoke GCC the way I showed in my email (with the -v
option and no extra options) it will print out the default search path
and you can see what is expected by that install of GCC.

> if I add the -I/usr/alpha-linux-gnu/include to the compile - now -
> that does work.   Thanks!  Not sure why its not picking it up
> automatically.

This shouldn't be needed.  But if you do use it I urge you to use

  -isystem /usr/alpha-linux-gnu/include

rather tha -I.  Otherwise you may get spurious compiler warnings for
content in the system header files.  See:
https://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html