On Thursday, 22 February 2018 at 00:34:59 UTC, kdevel wrote:
Is there a D equivalent of the C++ at method? I would like to
reformulate
repro2.d
---
void main ()
{
import std.stdio;
import std.container;
import std.range;
auto z = Array!char();
z.reserve(0xC000_0000);
z.capacity.writeln;
z.length.writeln;
for (uint u = 0; u < 0xC000_0000; ++u)
z.insert = 'Y';
int i = -1073741825;
i.writeln;
z[i] = 'Q';
z[i].writeln;
}
---
$ dmd -O -m32 repro2.d
$ ./repro2
3221225472
0
-1073741825
Q
such that it fails like the 64 bit version:
$ dmd -O -m64 repro2.d
$ ./repro2
3221225472
0
-1073741825
core.exception.RangeError@.../dmd2/linux/bin64/../../src/phobos/std/container/array.d(650):
Range violation
----------------
??:? _d_arrayboundsp [0x440d22]
.../dmd2/linux/bin64/../../src/phobos/std/container/array.d:650
inout pure nothrow ref @nogc @safe inout(char)
std.container.array.Array!(char).Array.opIndex(ulong) [0x43bb0f]
repro2.d:14 _Dmain [0x43afff]
Well in a 32bit program the value 0xBFFF_FFFF(-1073741825) is
clearly inside the array. The Array class uses an size_t
internaly for storing the length/capacity, that is uint in a
32bit program and ulong in a 64bit program. In the 64bit the
value (0xFFFF_FFFF_BFFF_FFFF)(-1073741825) is larger than
0xC000_000 so it will be out of bounds in this case.
If you want any negative integer to be out of bounds the capacity
cannot be larger than 0x7FFF_FFFF in 32bit programs.
But this behavior is strange. Well the really strange/bad part is
that it's allowed by the compiler in the first place. I would be
very happy if a user was forced to make an explicit cast for int
<-> uint conversions. Like we have to do for long -> int
conversions. Also signed/unsigned comparisons should be strictly
outlawed by the compiler.
Eg:
uint a = 3;
int b = -1;
assert(a > b); //No idea what should happen here.
