[Issue 3669] New: Default parameter initialization of size_t can result in errors about implicit conversions to uint

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3669

           Summary: Default parameter initialization of size_t can result
                    in errors about implicit conversions to uint
           Product: D
           Version: 2.038
          Platform: x86_64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: jmdavisProg at gmail.com


--- Comment #0 from Jonathan M Davis <jmdavisProg at gmail.com> 2010-01-03 20:28:01 PST ---
Okay. Basically, under some circumstances, a default initialization for a
function parameter of type size_t with an argument of type size_t results in a
complaint about uint not being convertible to size_t. For instance, given the
following code:

size_t getNum(size_t num = DEF_NUM)
{
    return num;
}

void main()
{
    size_t num = getNum();
}

size_t DEF_NUM = 10;

you get the error

temp.d(5): Error: cannot implicitly convert expression (DEF_NUM) of type size_t
to uint

However, if you put the declaration of DEF_NUM first:

size_t DEF_NUM = 10;

size_t getNum(size_t num = DEF_NUM)
{
    return num;
}

void main()
{
    size_t num = getNum();
}

it will compile. So, it appears to have something to do with the declaration
order. If you were to replace getNum() with DEF_NUM, that is

void main()
{
    size_t num = DEF_NUM;
}

size_t DEF_NUM = 10;

then it compiles. It doesn't matter whether DEF_NUM or main is declared first,
it compiles either way. So, it appears to have something to do with default
initialization of a function parameter. In any case, all of the variables
involved are size_t, so there shouldn't be any complaints about conversions. I
assume that size_t is actually uint and that there's some kind of aliasing
issue, but I don't know.

The compiler version that I'm using is actually 2.0.39, not 2.0.38, but 2.0.39
wasn't in the list - too new I guess. Also, my machine is x86_64, so I put
x86_64 for the hardware, but since dmd is only 32 bit, I doubt that it matters.
But that's my hardware, so that's what I put.

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