Re: RFC: Access TLS symbols without DWARF debuginfo

[Daniel Jacobowitz <drow at false dot org>]

On Fri, Aug 25, 2006 at 04:13:04AM +0200, Jan Kratochvil wrote:
> Hi,
> 
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=185337
> 
> currently if you have threaded (-lpthread) program compiled without debuginfo
> "-g" and you try to access TLS symbol you will get:
> 	(gdb) print thread_local
> 	Cannot access memory at address 0x0
> 
> as gdb tries to resolve TLS-offset as absolute memory reference.
> 
> In fact it occurs if you try to access "errno" on -lpthread program with
> debuginfo lower than -ggdb3.
> 
> Attached patch implements accessing them without the debuginfo suggestions as
> not always such associatet debuginfo is available.  It checks for
> 	SYMBOL_BFD_SECTION (msymbol)->flags & SEC_THREAD_LOCAL
> symbols, implements for them new `UNOP_MEMVAL_TLS' and reuses for them former
> `dwarf_expr_tls_address'.

Thanks for doing this.  It's a good idea, and the first step to not
needing libthread_db to do this - in most cases the gdbarch vector
should have enough knowledge.  And overall the patch looks very nice.

The same general comments apply as to your other patch, e.g. about a
ChangeLog.

Could you explain why you added a new kind of value for this?  I'd have
thought that when we wanted the address of the symbol, we should be
able to resolve it.  So instead of value_at_lazy_tls, we would resolve
the address using the target.  Expressions persist between threads and
executions, but values shouldn't.  That should simplify the code a
little.


-- 
Daniel Jacobowitz
CodeSourcery