GCC stack backtraces
Wed Aug 29 17:09:00 GMT 2012
On 08/29/2012 12:43 AM, Janne Blomqvist wrote:
> On Wed, Aug 29, 2012 at 10:22 AM, Ian Lance Taylor <firstname.lastname@example.org> wrote:
>> I've spent the last couple of days working on a stack backtrace library.
>> It uses the GCC unwind interface to collect a stack trace, and parses
>> DWARF debug info to get file/line/function information.
>> I expect to use this code not just for GCC proper, but also for libgo
>> (currently libgo uses Go code to parse DWARF, but that is not very
>> satisfactory as that code is only available if it has been imported into
>> the program). So I put it under a BSD license, although that is open
>> for discussion. Also in case it finds more uses elsewhere I wrote it in
>> reasonably portable C rather than C++.
>> Does this seem like something we could usefully add to GCC? Does
>> anybody see any big problems with it?
> I haven't looked at the code, but if it is async-signal-safe it could
> be interesting for gfortran. Currently in libgfortran we have a
> backtracing routine, originally written by FX Coudert IIRC, since
> rewritten by yours truly a few times, that uses _Unwind_Backtrace()
> from libgcc and then pipes the output via addr2line, if found. Since
> it's invoked from a signal handler when the program (user program, not
> the compiler!) crashes, it needs to be async-signal-safe. AFAIK the
> current implementation *should* fulfill that requirement. But
> something that would be async-signal-safe and won't need addr2line to
> get symbolic info would be a nice improvement,
libgcj also uses this technique. If this were merged, it would be
really nice to retrofit libgcj to use it as well.
Having this capability available from C and C++ code would also be
really nice. Several times in the past I have hacked together an
unwinder by calling _Unwind_Backtrace(), and then decoded the traces
off-line using addr2line. An easy, low-overhead way to add
function/line number information to a trace would be quite welcome.
I would almost say to put it in libgcc along side of
_Unwind_Backtrace(), but that doesn't seem the proper place for it. It
would be very convenient though.
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