toolchain/46490: libexecinfo only wokrs on amd64

[martin%NetBSD.org@localhost]

>Number:         46490
>Category:       toolchain
>Synopsis:       libexecinfo only wokrs on amd64
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon May 28 10:50:00 +0000 2012
>Originator:     Martin Husemann
>Release:        NetBSD 6.99.7
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD thirdstage.duskware.de 6.99.7 NetBSD 6.99.7 (MODULAR) #0: Sun 
May 27 23:21:43 CEST 2012 
martin%night-porter.duskware.de@localhost:/usr/src-clean/sys/arch/sparc64/compile/MODULAR
 sparc64
Architecture: sparc64
Machine: sparc64
>Description:

The new libexecinfo seems to be implemented using a technique that is gcc
specific and only works (with default compile flags) on amd64, where
.eh_frame_hdr and .eh_frame sections are generated by default.n

The corresponding test case seems to fail everywhere else right now.

The _Unwind_Backtrace() call calls back into "tracer" once, the t->n value
is still (size_t)~0U so this frame is skipped, then unwinding terminates
with reason 5 (end of stack) and zero frames are returned.

>How-To-Repeat:
Run t_backtrace for example on sparc64.

>Fix:
I am not sure this is fixable, may need some other technique.