On 2018-09-21 10:49:19 +0800, Liu Hao wrote: > 在 2018-09-20 23:58, Vincent Lefevre 写道: > > On 2018-09-20 23:21:23 +0800, Liu Hao wrote: > >> `2147483647` is an integer constant. This rule only describes floating > >> constants, so it does not apply. > > > > Actually the fact that it is a constant doesn't matter, but... > > The paragraph quoted by the previous message contains a sentence saying > '... and of floating constants are evaluated to a format ...'. While > all following paragraphs don't mention `floating constants` explicitly, > it is implied. Forgot what I said at that time. It's an integer constant, thus it is always evaluated *exactly* as an integer. Then, the rules for type conversions in a floating-point expression are the same, whether the values come from constants and non-constants. Thus if one does float a; int b; /* ... */ a + b; with FLT_EVAL_METHOD = 2, the evaluation type of a is long double, b is converted to the semantic type float, but its evaluation type is long double, so that its value should not change if representable as a long double. That's what FLT_EVAL_METHOD means. The *only* cases for which the precision and range need to be reduced to those of the semantic type if for assignment and cast, but here one just has an implicit conversion. -- Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
