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Re: The direction of malloc?

On Tue, 10 Dec 2013, Will Newton wrote:

> > One significant difficulty with building a replacement into glibc is
> > supporting malloc_set_state calls with data saved with a previous glibc
> > version - the problem that has so far prevented us from correcting malloc
> > alignment for powerpc32 without breaking emacs (bug 6527 - as noted in
> > that bug, it should be fixed for 32-bit x86 as well to support ISO C
> > extensions such as _Decimal128 properly, if a way to fix it is found).
> Is that actually possible? I thought malloc_get_state just returned an
> opaque pointer so I wasn't aware it could be written out to any kind
> of storage or last longer than the lifetime of a process.

The main purpose of malloc_get_state / malloc_set_state is for use by 
emacs.  If emacs adopted a better approach I'd happily deprecate them - 
turn them into compat symbols - but you still need to support them 
indefinitely with existing emacs binaries, as a matter of binary 
compatibility.  (Support could mean such binaries - binaries using the 
malloc_set_state compat symbol - use a different copy of malloc in libc 
from what all other binaries use, if necessary.)

Joseph S. Myers

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