Method signature differences in core modules on dmd and gdc?

[Gary Willoughby via Digitalmars-d-learn]

I've been recently trying GDC out to compile some D code and i'm 
running into the problem of differing function signatures in core 
modules.

For example:

stack.d:79: error: function core.memory.GC.calloc (ulong sz, uint 
ba = 0u) is not callable using argument types (ulong, BlkAttr, 
TypeInfo_Array)
stack.d:110: error: function core.memory.GC.realloc (void* p, 
ulong sz, uint ba = 0u) is not callable using argument types 
(string*, ulong, BlkAttr, TypeInfo_Array)
<snip>

These compile fine using DMD. Anybody know what the issue is here?