Corruption of shared data with multiple threads

[Johan Engelen via digitalmars-d-ldc]

Hi all,
   I am working on adding coverage analysis (like DMD's) to LDC.
It is a work in progress, but you can test the current status 
here: https://github.com/JohanEngelen/ldc/tree/coverage
It already works nicely, but the line count is not increased for 
all types of statements yet. I've been breaking my head on a 
problem with multithreaded programs.

This test program works fine (ldc2 -cov test.d)
void main() {
    fun(...);
}
void fun(...) {
     ...
}
and outputs the same line count as dmd does.
Making the program multithreaded, like this:
import std.concurrency;
void main() {
    spawn(&fun,...);
}
void fun(...) {
     ...
}
no longer works. (it actually used to work for me, but for some 
reason with a completely rebuilt druntime, it crashes). I've 
traced the problem back to the Cover[] gdata data structure in 
druntime/cover.d becoming corrupted somewhere during program 
execution. More specifically, in struct Cover, filename.length 
becomes corrupted somehow.

Is it a known issue, that we have some bugs with shared data + 
multiple threads?

Thanks,
   Johan

(LLVM 3.6, MSVC, x64)