[tor-bugs] #11047 [Tor]: Use -fno-omit-frame-pointer or -fasynchronous-unwind-tables options to make backtraces work better

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#11047: Use -fno-omit-frame-pointer or -fasynchronous-unwind-tables options to make
backtraces work better
---------------------------------+------------------------------------
 Reporter:  nickm                |          Owner:
     Type:  defect               |         Status:  new
 Priority:  normal               |      Milestone:  Tor: 0.2.5.x-final
Component:  Tor                  |        Version:
 Keywords:  tor-relay backtrace  |  Actual Points:
Parent ID:  #11046               |         Points:
---------------------------------+------------------------------------
 With GCC, the implicit or explicit use of the "omit-frame-pointer"
 optimization can interfere with generating backtraces on some
 architectures.  According to cypherpunks on #9299:

 > Stack trace unreadable if FPO enabled in general or used optimization
 options (then FPO applied selectively by compiler depends function's code)
 for x86 platform. It's not problem for x86_64 because GCC generates unwind
 tables there by default.
 > If to enable unwind tables by "-fasynchronous-unwind-tables" then stack
 trace readable with any optimizations.

 cypherpunks also notes that starting with GCC 4.6, -fomit-frame-pointer is
 on by default on several optimization levels.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/11047>
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