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Re: [PATCH] Initialize _r_debug for static applications.

On 04/10/2014 08:06 PM, Carlos O'Donell wrote:
> With Maciej's great work on reducing the difference between
> static and dyanmic executables, and with the addition of
> a functional main link map in static exectuables we can now
> usefully initialize _r_debug for static applications. This
> will allow future debuggers the ability to coalesce code
> paths which previously had to have special cases for static
> v.s. dyanmic.
> It also fixes this particular use case where gdb would like
> a consistent way to find the application link map for looking
> up TLS variables in both static and dynamic applications:
> The discussion touches on the fact that without _r_debug the
> debugger has to make various assupmtions while using
> libthread_db that contrains the implementation.
> This patch initializes the debug infrastructure during
> LIBC_START_MAIN, but only for static applications, by
> calling `_dl_debug_initialize (0, LM_ID_BASE)'. We pass 0 as
> the ldbase because it's a static application, and the runtime
> address of the loader doesn't matter. We pass LM_ID_BASE because
> we want to load, by default, the base link map, and that's what
> really matters.
> Tested on x86_64 with no regressions.
> Jan reports this works and that gdb can be patched to use
> _r_debug to access TLS variables in static applications
> while still using the current libthread_db calls normally
> used for dynamic applications.
> This removes one more difference between static and dynamic
> applications.
> Note: This does not attempt to cleanup the -Wundef warning
> for SHARED, which I am looking to fix in another patch so
> we still use `#ifndef SHARED' (Makeconfig needs to be fixed
> to use -DSHARED=0 and -DSHARED=1 IMO to make this work correctly).
> OK to checkin?
> Cheers,
> Carlos.
> 2014-04-10  Carlos O'Donell  <>
	[BZ #16831]
> 	* csu/libc-start.c (LIBC_START_MAIN) [!SHARED]: Call
> 	_dl_debug_initialize.

Filed 16831 for user visible change to _r_debug interface.


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