Re: [patch] mem_node shrink

[Richard Stallman]

    > So I think MOST_POSITIVE_FIXNUM should be replaced with something
    > guaranteed to be right.  Define a constant to serve as the width of
    > that field, and use the same constant here in something like -((-1) <<
    > MEM_NODE_SIZE_WIDTH).

    If GC_MALLOC_CHECK is defined, xmalloc and xrealloc calls
    mem_insert.  On 64-bit system, if neither USE_MMAP_FOR_BUFFERS nor
    REL_ALLOC are used, xmalloc and xrealloc may grow buffer text up
    to the size which fits into integer, but not into 28-bit bitfield.
    So, the bitfield should be wide enough, i.e. have width
    BITS_PER_EMACS_INT - 4.

There are two questions here.  You're talking about whether the field
is wide enough.  The other is how to write this error check:

>     +  if (size > MOST_POSITIVE_FIXNUM)
>     +    abort ();