Re: GDB support for thread-local storage

Jim Blandy
2002-06-19T19:20:47Z

Daniel Berlin <dberlin@dberlin.org> writes:
> > Unfortunately, Dwarf 2 location expressions cannot perform function
> > calls in the inferior.
>
> Errr, buzz.
>
> See DW_OP_call_* in dwarf3

(As I wrote that sentence, I was wondering whether I should clarify
this point.)

The function one may need to invoke to find thread-local storage,
__tls_get_addr, is an actual native code function, in the dynamic
linker. The DW_OP_call_* operations allow a Dwarf expression to call
another Dwarf expression like a function. But you can't use the
DW_OP_call_* operations to invoke machine-language functions in the
inferior.

> It's not just turing complete anymore, one could probably write useful
> application extensions in dwarf3.
> Scary.

I thought so too, but then I noticed that there are no memory store
operations. You can do stuff on the stack, but you can't modify
memory, or do any I/O. Grave omissions, which should be rectified
immediately.