If your code counters what I said, show it.

Are you saying that the following works:

#include <stdio.h>

cmpFsFd( float s, double d ) {
    float tmp = (float)d;
    return s == tmp ? 1 : 0;
}

int main(void) {
   double nv = 2.0 / 3;
   float foo = 2.0 / 3;

   if( foo == nv ) printf("True ");
   else printf("False ");

   if( cmpFsFd( foo, nv )) printf("True\n");
   else printf("False\n");

   return 0;
}
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And that the following doesn't?

#include <stdio.h>

int main(void) {
   double nv = 2.0 / 3;
   float foo = 2.0 / 3;
   volatile float nv_as_float = (float)nv;

   if( foo == nv ) printf("True ");
   else printf("False ");

   if( foo == nv_as_float ) printf("True\n");
   else printf("False\n");

   return 0;
}
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That makes no sense to me.