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Re: SYS_sbrk removal proposal



Den 2017-12-19 kl. 13:12, skrev Sevan Janiyan:
Hello,

On 12/19/17 11:51, Anders Magnusson wrote:
Sounds good :-)

Just a note here:

about 15-20 years ago I did a test by removing the brk(2) syscall and
replacing its use
in malloc() by mmap(), and also add a libc wrapper for brk() that
mmap'ed MAXDSIZ/2 if ever called (as a fallback).

This approach worked very well for everything tested _except_ emacs.
There were something in emacs dump logic that seemed to expect that
brk() were continuing just above bss, or something.
I didn't go deeper into this back then.

Anyway, it might be an idea to revisit this.  IMHO it would be really
nice if brk(2) could be declared obsolete :-)
Just as a heads up, I believe the FreeBSD folks went through this with
their ARMv8 support and looking up the notes on their wiki, indeed,
emacs was the fallout.
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=213862

Last lines are the most interesting:

Ed Maste freebsd_committer 2017-11-20 21:11:02 UTC

The GNU bug report claims that it is fixed in 26.1

So, unless someone want to compile an old emacs, it do not seem like an issue anymore :-) -- Ragge



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