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Paul Eggert authored
libgmp calls ‘abort’ when given numbers too big for its internal data structures. The numeric limit is large and platform-dependent; with 64-bit GMP 6.1.2 it is around 2**2**37. Work around the problem by refusing to call libgmp functions with arguments that would cause an abort. With luck libgmp will have a better way to do this in the future. Also, introduce a variable integer-width that lets the user control how large bignums can be. This currently defaults to 2**16, i.e., it allows bignums up to 2**2**16. This should be enough for ordinary computation, and should help Emacs to avoid thrashing or hanging. Problem noted by Pip Cet (Bug#32463#71). * doc/lispref/numbers.texi, etc/NEWS: Document recent bignum changes, including this one. Improve documentation for bitwise operations, in the light of bignums. * src/alloc.c (make_number): Enforce integer-width. (integer_overflow): New function. (xrealloc_for_gmp, xfree_for_gmp): Move here from emacs.c, as it's memory allocation. (init_alloc): Initialize GMP here, rather than in emacs.c. (integer_width): New var. * src/data.c (GMP_NLIMBS_MAX, NLIMBS_LIMIT): New constants. (emacs_mpz_size, emacs_mpz_mul) (emacs_mpz_mul_2exp, emacs_mpz_pow_ui): New functions. (arith_driver, Fash, expt_integer): Use them. (expt_integer): New function, containing integer code that was out of place in floatfns.c. (check_bignum_size, xmalloc_for_gmp): Remove. * src/emacs.c (main): Do not initialize GMP here. * src/floatfns.c (Fexpt): Use expt_integer, which now contains integer code moved from here. * src/lisp.h (GMP_NUMB_BITS): Define if gmp.h doesn’t.
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