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[[!meta copyright="Copyright © 2011, 2013 Free Software Foundation, Inc."]]
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If you need to debug something in the early `ld.so` startup, and can't refrain
from good old `printf` debugging, there is a caveat: the available API in
`ld.so` is rather limited. See the few functions is `dl-sysdep.c`. For
example, there's a private `__libc_write`, which you should be able to use for
writing to FD stderr -- but, at early `ld.so` startup, this isn't usable as
`_hurd_init_dtable` is still all zeros, etc. To get you started, here is a
simple [[dl-sysdep.c.patch]] to get access to the Mach console.
[[!message-id desc="Original submission" "87y5vrpnvi.fsf@gnu.org"]].
Can this be integrated with the other debugging printf functions from
`elf/dl-misc.c` (`_dl_debug_vdprintf`) ([[!taglink open_issue_glibc]])?
In 2013-01, the [[microkernel/mach/gnumach/interface/syscall/mach_print]]
[[system_call]] has been added to [[GNU Mach|microkernel/mach/gnumach]].
It is available when the kernel is built with the in-kernel kdb debugger.
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