Giving up

[Walter Bright]

On 8/5/2022 9:43 AM, Max Samukha wrote:
> Both "123." and "123.E123" is valid C. For some reason, D only copied the former.

It's to support UFCS (Universal Function Call Syntax). The idea with C 
compatible aspects of D is to not *silently* break code when there's a different 
meaning for it. And so, these generate an error message in D (although the error 
message could be much better).

So, does it work with ImportC?

test2.c:
   float z = 85886696878585969769557975866955695.E0;
   long double x = 0x1p-16383;

dmd -c test2.c
   test2.c(3): Error: number `0x1p-16383` is not representable

So the first one does compile as expected with ImportC. Let's try gcc and clang:

gcc -c test2.c
   test2.c:3:1: warning: floating constant truncated to zero [-Woverflow]
    long double x = 0x1p-16383;
    ^

clang -c test.c
   test2.c:3:17: warning: magnitude of floating-point constant too small for 
type 'double'; minimum is 4.9406564584124654E-324 [-Wliteral-range]
   long double x = 0x1p-16383;


aaaand, the truth comes out. It is not representable, it is truncated to 0. 
Technically, ImportC should accept it. But if it does, doesn't it mislead users 
into thinking it is non-zero?

We've got the right choice here, but it's definitely a judgement call.