Re: Alignment of Lisp_Subr

["Stephen J. Turnbull" <stephen@xemacs.org>]

>>>>> "Gaute" == Gaute B Strokkenes <Gaute> writes:

    Gaute> On 13 nov 2003, stephen@xemacs.org wrote:

    >> There may be issues with Lisp objects with tagbits at the
    >> bottom.  I know XEmacs had some problems on recent glibc, which
    >> were never properly diagnosed.  It's probable that this was due
    >> to excessive cleverness in optimizing space use of malloc
    >> blocks, but if you do run into weirdness (we were crashing)
    >> feel free to ping me and I'll dig up the thread.

    Gaute> Are you saying that glibc malloc does not return blocks
    Gaute> that are sufficiently aligned?  My copy of the glibc manual
    Gaute> says:

No, I'm saying that XEmacs (which has had tagbits in the lower bits
for a couple of years now) was crashing for unknown reasons.  Wolfram
Gloger thought it might have to do with tagbits in Lisp objects, but
the bug was never identified.  A separate issue from alignment, but it
is related to moving tagbits from high bits to low bits, which was one
main difference between XEmacs (which had problems) and GNU Emacs
(which didn't) at that time (about a year ago).


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