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Re: Removal of unexec support from glibc malloc

From: Philipp Stephani
Subject: Re: Removal of unexec support from glibc malloc
Date: Mon, 18 Jan 2016 22:10:09 +0000

Daniel Colascione <address@hidden> schrieb am Mo., 18. Jan. 2016 um 21:05 Uhr:
On 01/18/2016 12:02 PM, Eli Zaretskii wrote:
>> From: Paul Eggert <address@hidden>
>> Date: Mon, 18 Jan 2016 11:50:31 -0800
>> Emacs could live without the current unexec in a semi-portable way by doing what
>> XEmacs does, which is to write out data and mmap it in later (sorry, don't know
>> the details). There are other possibilities, e.g., have unexec write out the
>> state in the form of C files that are compiled and linked in the usual way to
>> build a faster-starting executable (this would be an Emacs API change, though).
>> Any such changes would take some time to hack into something reliable and
>> portable, and so will have to wait until after Emacs 25 is out.
> There's also what the MS-Windows port does (temacs allocates off a
> static array), which AFAIK is entirely portable, and doesn't require
> mmap.  See w32heap.c.

It's a portable stopgap, maybe, but a real portable dumper would be
_much_ better, since then Emacs could be a much safer
position-independnent executable (as a portable dumper would relocate
the dump as it loads, since it knows where all the pointers are).

I completely agree. Also see the existing bugs https://debbugs.gnu.org/cgi/bugreport.cgi?bug=20215 and https://debbugs.gnu.org/cgi/bugreport.cgi?bug=20868.
Does anybody have a rough estimate what would be required to make the dumper really portable? 

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