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Re: frame unwinding patches
- From: Ulf Hermann <ulf dot hermann at qt dot io>
- To: Jan Kratochvil <jan dot kratochvil at redhat dot com>, Milian Wolff <mail at milianw dot de>
- Cc: <elfutils-devel at sourceware dot org>, Mark Wielaard <mark at klomp dot org>
- Date: Tue, 4 Apr 2017 10:24:45 +0200
- Subject: Re: frame unwinding patches
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- In the example above, the address points into libnvidia-glcore.so and as
such not compiled by my colleague but rather provided by NVidia as a binary
blob. When you only got a binary blob and have to make do with it, you cannot
tell people to "just fix the compiler invocation".
This is their problem they support a vendor who cripples usage of their
products. There is also Intel and AMD.
Sorry, but I cannot tell everybody with binary-only graphics drivers
that they cannot use perfparser. That's probably the majority of
embedded devices and a large number of desktops.
- Some JIT compilers, like QV4, actually embed frame pointers into their
dynamic code, but do not go the extra mile for generating DWARF data or
asynchronous unwind tables. That is another case where the patches by Ulf
excel and make elfutils much more useful.
In such case elfutils could provide some workaround with a new eu-stack option:
Frame pointers are the easiest way to include unwinding information into
a binary and they require less work from the compiler than other
methods. With JIT compilers, compile time matters much more than with
ahead of time compilers. Also, adding extra code to the compiler has to
be justified in that case as the compiler is shipped inside the
libQt5Qml binary and loaded into memory whenever you run some QML.
So, I think frame pointers are a perfectly valid option for unwinding
and should be supported.