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Re: RFC: libiberty PATCH to disable demangling of ancient mangling schemes
- From: Pedro Alves <palves at redhat dot com>
- To: Jakub Jelinek <jakub at redhat dot com>, Nick Clifton <nickc at redhat dot com>
- Cc: Jason Merrill <jason at redhat dot com>, Ian Lance Taylor <iant at google dot com>, Richard Biener <richard dot guenther at gmail dot com>, matz at gcc dot gnu dot org, Scott Gayou <sgayou at redhat dot com>, Tom Tromey <tom at tromey dot com>, gcc-patches List <gcc-patches at gcc dot gnu dot org>, Binutils <binutils at sourceware dot org>, GDB Patches <gdb-patches at sourceware dot org>
- Date: Fri, 7 Dec 2018 16:11:46 +0000
- Subject: Re: RFC: libiberty PATCH to disable demangling of ancient mangling schemes
- References: <email@example.com> <CAFiYyc1gTSXgSiJSFKEWaE0UTGbi45-mWHKJnUb4Wvjp86bbFQ@mail.gmail.com> <firstname.lastname@example.org> <CAKOQZ8zspME4gzoRw4xgFcShoqeUfp_e=Og=4S-yKn4EehokeA@mail.gmail.com> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <CADzB+2n6kz=9zLzordWp3gqW+hrLHBhQJ-5p5Lt8Stqv97=nBw@mail.gmail.com> <email@example.com> <20181207104011.GD12380@tucnak>
Adding gdb-patches, since demangling affects gdb.
On 12/07/2018 10:40 AM, Jakub Jelinek wrote:
> On Fri, Dec 07, 2018 at 10:27:17AM +0000, Nick Clifton wrote:
>>>> Looks good to me. Independently, do you see a reason not to disable the
>>>> old demangler entirely?
>>> Like so. Does anyone object to this? These mangling schemes haven't
>>> been relevant in decades.
>> I am not really familiar with this old scheme, so please excuse my ignorance
>> in asking these questions:
>> * How likely is it that there are old toolchain in use out there that still
>> use the v2 mangling ? Ie I guess that I am asking "which generation(s)
>> of gcc used v2 mangling ?"
> GCC 3.0 and up used the new (Itanium C++ ABI) mangling, 2.95 and older used the old
> mangling (2.96-RH used the new mangling I believe).
> So you need compiler older than 17.5 years to have the old mangling.
> Such a compiler didn't support most of the contemporarily used platforms
> though at all (e.g. x86-64, powerpc64le, aarch64, I believe not even
I guess the question would be whether it is reasonable to expect
that people will still need to debug&inspect (with gdb, c++filt, etc.)
any such old binary, and that they will need to do it with with modern
tools, as opposed to sticking with older binutils&gdb, and how often
would that be needed.
I would say that it's very, very unlikely, and not worth it of the
Last I heard of 2.95-produced binaries I think was for some ancient gcc-2.95-based
cross compiler that was still being minimally maintained, because it was needed
to build&maintain some legacy stuff. That was maybe over 8 years ago, and
it was off trunk. It's probably dead by now. And if isn't dead,
whoever maintains the compiler off trunk certainly can also maintain old-ish
binutils & gdb off trunk.