Re: [PATCH 3/4] perf tools: Check libunwind for availability of dwarfparsing feature

From: Jean Pihet
Date: Tue Sep 24 2013 - 08:04:10 EST

Hi Jiri, Will,

On 24 September 2013 12:06, Will Deacon <will.deacon@xxxxxxx> wrote:
> On Tue, Sep 24, 2013 at 10:34:50AM +0100, Jiri Olsa wrote:
>> On Tue, Sep 24, 2013 at 10:55:32AM +0200, Jean Pihet wrote:
>> > Ping on the series. The two patches above (3/4 and 4/4) are generic
>> > while the two others are impacting ARM only.
>> > Is it possible to get an Ack for the generic ones?
>> I'm fine with those changes.. still I'm sort of worried about
>> current DWARF unwind users (but not sure if there're any),
>> who depends on packaged libunwind compiled without
>> --enable-debug-frame option.
> Since x86 is the only architecture using libunwind with perf at the moment,
> and I'd expect it to use .eh_frame for unwinding, I'm also not sure there
> are any existing users to worry about.

>> I've seen your libunwind patch to make it default, but
>> not sure if it was accepted.. if not, maybe we should
>> detect this and build that code conditionaly.
> It certainly defaults to "on" for ARM, but other architectures have to
> enable it explicitly afaict.
Yes that is correct.
This patch (3/4) detects if the debug frame code is enabled in
libunwind and uses the lib only if it is the case.
Users that want the feature have to enable it explicitly; the commit
description documents how to do that.

So I think we are safe here.

> Will

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