I'm creating a minimal DRuntime (for messing around). Right now, I have a very basic program that doesn't even link to the C runtime, and uses syscalls for everything. I'm trying to implement alloca so that I can parse arguments (long story), and so I went to druntime/src/rt/alloca.d.

Everything I found there looked OK except for _pastdata.
I saw the comment before the function declaration declaring _pastdata to be an extern C variable, and I defined it as such. DMD failed to compile, saying that it cannot load from TLS. I then added '__gshared' to the declaration, but DMD failed again, saying "Cannot directly load global variable with PIC code." Is there any way I can get alloca to work?