Fix #5114 - Avoid same-symbol qualifier-difference case falling into wrong cast branch

[gulugulubing]

It is related to #5114. The root cause is the const(I) -> I contract-context conversion always called DtoCastClass, then due to I.isBaseOf(I, ...) return false, the program accidently fall into the DtoDynamicCastInterface which is ObjC-only and ends in unreachable for non-ObjC.

So I added an early guard for same-symbol qualifier-difference case there.

The patch is only in tocall.cpp, while objcgen.cpp and classes.cpp are modified just because of removing trailing blank.

[thewilsonator]

please remove the whitespace changes

[gulugulubing]

please remove the whitespace changes

OK, is it accpetable:
For files with actual content changes, I kept the trailing whitespace cleanup (since we're already modifying these files)
For files with only whitespace changes, I reverted them completely to avoid unnecessary diffs.

[JohanEngelen]

looks like no change was made here, except for the dangerous-looking change from heap allocated dthis to stack allocated. Possibly use-after-scope. Revert this change?

[gulugulubing]

Does the original heap allocated dthis cause potential leak-like lifetime?

[JohanEngelen]

that's for you to prove ;)
A mem leak is much more benign than a use-after-scope bug.

[gulugulubing]

In the original heap version, there are no deallocation in the caller and callee, so I think there is a mem leak.

And use-after-scope does not happen, because DtoCastClass only consumes the pointer immediately and does not store it.

At last, I am a little confused here: do you mean the original code intentionlly choose mem-leak to avoid use-after-scope?

[gulugulubing]

In classes.cpp, there is similar stack allocation:

    // get class ptr
    LLValue *v = DtoRVal(val);
    // cast to size_t
    v = gIR->ir->CreatePtrToInt(v, DtoSize_t(), "");
    // cast to the final int type
    DImValue im(Type::tsize_t, v);
    return DtoCastInt(loc, &im, _to);

So I am not sure which is best practise here.

[JohanEngelen]

nitpick: line 11 already tests compilation, so you can remove line 10