use of volatile ?

[Richard Bos]

Two, of course, but isn't it usually spelled with a 'k' and preceded
by Brekekekex?

Have you been lurking in the Shedde?

Richard

 

[David Thompson]

You should try compiling any code before you post it here.

<snip corrections to types>

But the compiler doesn't catch everything. Even with required
diagnostics corrected the example doesn't work as intended.

In order to 'ensure' -- in scarequotes because the implementation is
allowed to weasel out of really doing volatile, but at least as far as
the generally accepted _intent_ -- that the "I/O port" is in fact read
twice, not just read once and reused, what you need is:
/* here */ volatile char * ioport = suitable_initialization;
/* not here */ char ch = * ioport; /* etc. */

or if you prefer
char * ioport = whatever;
char ch = * (volatile char *) ioport;

And this is leaving aside that plain char may be signed at the
implementation's option, so you very likely want unsigned char.

- formerly david.thompson1 || achar(64) || worldnet.att.net