I've looked more closely into this one. Something goes bad when d2f bytecode instruction is exectued in this case. the implementation in intrp/icode.h looks innocent enough, but I'm not sure what should happen precisely when max double is assigned to a float in C. I've written a test case, and attached it, so it'd be nice if you could run it on your netbsd-ppc machine and report the results.
NetBSD/ppc 2.0 beta, gcc 3.3.3: d = 1.79769e+308 f = inf g=inf d = 1 f = 7fefffff g=ffffffff f.f = 3.40282e+38 f.i = 7f7fffff
OpenBSD/sparc 3.4, gcc 2.95.2 d = 1.79769e+308 f = Inf g=Inf d = 7fefffff f = ffffffff g=7f800000 f.f = 3.40282e+38 f.i = 7f7fffff
Darwin 6.8, apple cc d = 1.79769e+308 f = Inf g=Inf d = 7fefffff f = ffffffff g=7f800000 f.f = 3.40282e+38 f.i = 7f7fffff
the behavior seems consistent to me what is the result at your place?
The only thing that's consistent is the last line :) Looks like my test was broken, could you try this version on NetBSD ppc?
I suspect that d2f is broken in the interpreter. The Java language spec demands that in case of overflow the value of float is a signed infinity, but the C standard says oveflow results in undefined behaviour. So I assume we'd have to check whether the double is representable as a float before we convert it, and handle the special cases that would invoke undefined behaviour ourself.
I'm working on a patch.
cheers, dalibor topic
#include <stdio.h>
union dtype {
double d;
int l [sizeof(double)/sizeof(int)];
};
typedef union dtype dtype;
union ftype {
float f;
int i[sizeof(float)/sizeof(int)];
};
typedef union ftype ftype;
void printhex(const char * name, const int * word, int len) {
int i;
printf("%s = ", name);
for (i = 0; i < len; ++ i) {
printf(" %x", word[i]);
}
puts("");
}
int main(void) {
dtype d;
ftype f;
ftype g;
printf("sizeof(double) = %d\n", sizeof(double));
printf("sizeof(float) = %d\n", sizeof(float));
printf("sizeof(int) = %d\n", sizeof(int));
printf("sizeof(long) = %d\n", sizeof(long));
printf("sizeof(long long) = %d\n", sizeof(long long));
printf("sizeof(dtype.l) = %d\n", sizeof(d.l));
printf("sizeof(ftype.i) = %d\n", sizeof(f.i));
d.d = 1.7976931348623157E308;
f.f = d.d;
g.f = (float) d.d;
printf("d = %g\t f = %g\t g=%g\n", d.d, f.f, g.f);
printhex("d", d.l, sizeof(d.l)/sizeof(int));
printhex("f", f.i, sizeof(f.i)/sizeof(int));
printhex("g", g.i, sizeof(g.i)/sizeof(int));
/*
printf("d = %Lx\t f = %x\t g=%x\n", d.l, f.i, g.i);
*/
f.f = 3.4028234663852885981e+38f;
printf("f.f = %g\n", f.f);
printhex("f.i", f.i, sizeof(f.i)/sizeof(int));
g.f *= -1.0;
printf("g.f = %g\n", g.f);
printhex("g.i", g.i, sizeof(g.i)/sizeof(int));
return 0;
}
