On 22/08/2012 15:58, Jeff B wrote:
On 08/21/2012 06:40 PM, Jeff B wrote:
(int)floatVarA = 0.000000 <<=== initial value 0??
On 08/22/2012 03:50 AM, Andrew Haley wrote:
The initial value is zero because there is garbage in Float Register 0.
floatVarA = 1234.000000
Now Float Register 0 contains 1234.0 .
(int)floatVarA = 1234.000000 <<=== changed
Which gets printed out.
floatVarB = 5678.000000
Now Float Register 0 contains 5678.0 .
(int)floatVarA = 5678.000000 <<=== changed again
Which gets printed out.
floatVarA = 1234.000000
etc...
Moral: undefined behaviour can do anything.
Andrew.
OK, then I guess the presence of the cast makes it OK for the compiler
to pull the bits for a variable from somewhere other than where the
variable actually is.
So, while we are at it, what other casts should I avoid?
Thanks.
You are still missing the point.
Avoid writing code with undefined behaviour. Do not lie to your
compiler. Do not tell it "here is a float" and pass it an integer. Use
"-Wall" to let the compiler help you avoid such mistakes.
It is perfectly okay to cast a float to an int - but it is not okay to
do so and then expect the compiler to treat it as a float. So you can
write this:
printf("(int) floatVarA = %d\n", (int) floatVarA);
Then you are casting the float to an int legally (1234.0 will turn into
1234), then passing that int to printf, with a format string that tells
printf to expect an int and print it out.
