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Re: Preview: portable dumper

From: Philipp Stephani
Subject: Re: Preview: portable dumper
Date: Fri, 16 Feb 2018 17:00:52 +0000

Andy Moreton <address@hidden> schrieb am Fr., 16. Feb. 2018 um 12:31 Uhr:
On Fri 16 Feb 2018, Eli Zaretskii wrote:

>> Date: Thu, 15 Feb 2018 15:34:13 -0800
>> From: Daniel Colascione <address@hidden>
>> Cc: Eli Zaretskii <address@hidden>, Angelo Graziosi <address@hidden>,
>>  address@hidden
>> I do wonder whether it makes sense to try to copy the dump into the Emacs executable itself instead of
>> leaving it as a separate file. We could do it independently of executable format by defining a data array in static
>> storage that's initially full of, say, 15MB of zeroes prefixed by a long random header (like a MIME boundary),
>> then, after we generate emacs.pdmp, copying the dump file into the executable at the place where we see
>> that random header. If the dump turns out to be bigger than that 15MB, we can fail the build and ask the user
>> to enlarge the array.
>> I don't know of any executable format for which this scheme would fail.
> Wouldn't that make the dumper stuff less portable, in the sense that
> it would need to be compatible with low-level details of executable
> file formats on various systems?
> At least on non-ELF systems, AFAIK the flexibility of putting
> arbitrary sections into an executable is lower than desired.  For
> example, before Emacs 25 the MS-Windows build would create a special
> section for the initialized Emacs data, which had the annoying effect
> of running afoul of 'strip', because Binutils don't know about this
> section, and therefore stripping would produce a dysfunctional
> executable.  It also prevented re-dumping Emacs, something we had in
> the past and I'd like us to have again in the future.
> Wouldn't copying the dump into the executable hit the same problems,
> at least in principle?

I don't understand the desire to put the dump within the eamcs
executable, as I thought the whole point of this exercise was to avoid
dodgy manipulation of executable file formats.

I agree. We already ship a lot of files that are expected at certain locations, like the Emacs Lisp files or the files in `data-directory', why should the pdump file be different? 

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