increasing var twice in a statement

[jlh]

> Can anybody tell me what output the following program snippet
> should produce according to C standard:

I think this case produces undefined behavior, so by the C
standard, 9 would be as correct as 10 or 42.  Compiling your code
with "-O2 -Wall" even produces a warning:

a.c:5: warning: operation on 'b' may be undefined

The reason is that you're modifying a variable twice within the
same two sequence points.  See

http://en.wikipedia.org/wiki/Sequence_point

jlh