DMD doesn't follow section 5.2.4.2.2 Characteristics of floating types.
Specifically:
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Except for assignment and cast (which remove all extra range and precision), the values yielded by operators with floating operands and values subject to the usual arithmetic conversions and of floating constants are evaluated to a format whose range and precision may be greater than required by the type. The use of evaluation formats is characterized by the implementation-defined value of FLT_EVAL_METHOD.
-1 indeterminable;
0 evaluate all operations and constants just to the range and precision of the type;
1 evaluate operations and constants of type float and double to the range and precision of the double type, evaluate long double operations and constants to the range and precision of the long double type;
2 evaluate all operations and constants to the range and precision of the
long double type.
All other negative values for FLT_EVAL_METHOD characterize implementation-defined behavior.
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Typically the default value of __FLT_EVAL_METHOD__ is 0. DMD evaluates operations at compile-time as-if __FLT_EVAL_METHOD__ is 2.
e.g:
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#include <stdint.h>
#include <stdlib.h>
int main()
{
int64_t a = INT64_MIN;
int64_t b = INT64_MAX;
double c = 0.0;
if (-1 != (a + b) + c) abort();
if (-1 != (INT64_MIN + INT64_MAX) + 0.0) abort();
if ( 0 != a + (b + c)) abort();
if ( 0 != INT64_MIN + (INT64_MAX + 0.0)) abort(); // fails
if ( 0 != a + (double)(b)) abort();
if ( 0 != INT64_MIN + (double)(INT64_MAX)) abort(); // fails
}
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