Coercing float into unsigned char on ARM vs. Intel

When I run the following C code on an Intel machine...

float f = -512;
unsigned char c;

while ( f < 513 )
{
    c = f;
    printf( "%f -> %d\n", f, c );
    f += 64;
}

...the output is as follows:

-512.000000 -> 0
-448.000000 -> 64
-384.000000 -> 128
-320.000000 -> 192
-256.000000 -> 0
-192.000000 -> 64
-128.000000 -> 128
-64.000000 -> 192
0.000000 -> 0
64.000000 -> 64
128.000000 -> 128
192.000000 -> 192
256.000000 -> 0
320.000000 -> 64
384.000000 -> 128
448.000000 -> 192
512.000000 -> 0

However, when I run the same code on an ARM device (in my case an iPad), the results are quite different:

-512.000000 -> 0
-448.000000 -> 0
-384.000000 -> 0
-320.000000 -> 0
-256.000000 -> 0
-192.000000 -> 0
-128.000000 -> 0
-64.000000 -> 0
0.000000 -> 0
64.000000 -> 64
128.000000 -> 128
192.000000 -> 192
256.000000 -> 0
320.000000 -> 64
384.000000 -> 128
448.000000 -> 192
512.000000 -> 0

As you can imagine, this sort of difference can introduce horrible bugs in cross-platform projects. My questions are:

1. Was I wrong to assume that coercing a float into an unsigned char would yield the same results on all platforms?

2. Could his be a compiler issue?

3. Is there an elegant workaround?