integer overflow in mpn/get_d.c from GMP 5.1.2

[Vincent Lefevre]

In GMP 5.1.2, there's an integer overflow in mpn/get_d.c:

  if (UNLIKELY ((unsigned long) (GMP_NUMB_BITS * size)
                > (unsigned long) (LONG_MAX - exp)))

It should be replaced by:

  if (UNLIKELY ((unsigned long) (GMP_NUMB_BITS * size)
                > (unsigned long) LONG_MAX - exp))

This integer overflow triggers the following failure

mpn_get_d wrong on denorm
  n=1
  exp   -1020
  sign  0
  got   =[00 00 00 00 00 00 F0 7F] inf
  want  =[00 00 00 00 00 00 30 00] 8.9002954340288055324e-308
Aborted (core dumped)
FAIL: t-get_d

with

gcc (Debian 20130917-1) 4.9.0 20130917 (experimental) [trunk revision 202647]

GNU MP config.status 5.1.2
configured by ./configure, generated by GNU Autoconf 2.69,
  with options "'--disable-shared' 'CC=gcc-snapshot' 'CFLAGS=-march=native -O3 -flto=jobserve -fuse-linker-plugin'"

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)