Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Mon, 27 Nov 2006 12:23:14 -0600

Eric Norum wrote:

static inline void
writethree(int *p)
{
    short *palias = (short *)p;
   *palias = 3;
}

int
testalias()
{
    int value = 12345678;
    writethree(&value);
    return value;
}

One might expect that the value returned from testalias() would be

12345678 with either its most-significant 16 bits or least- significant

16 bits set to 3 (on most architectures).

....
One would be wrong, though.

I don't think life is quite as bad as it might seem; if you take off the

"static inline" keywords from writethree(), I suspect the optimizer may

not be able to be quite as aggressive in throwing out code - please

experiment and respond to that suggestion.

Since we don't (shouldn't?) have any C routines in base that are marked

as "static inline", I don't think our problems are as large as you make

out them to be. I suspect the rules for C++ are subtly different, so it

would also be interesting to see what using the C++ compiler generates.

- Andrew
--
There is considerable overlap between the intelligence of the smartest
bears and the dumbest tourists -- Yosemite National Park Ranger

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System