Minor fixups for intmax_t→mpz_t conversion

* src/alloc.c (mpz_set_intmax_slow): Tighten assertion.
Work even in the unlikely case where libgmp uses nails.
* src/data.c (FIXNUMS_FIT_IN_LONG): New constant.
(arith_driver): Use it to tighten compile-time checks.
* src/lisp.h (mpz_set_intmax): Do not assume that converting
an out-of-range value to ‘long’ is harmless, as it might raise
a signal.  Use simpler expression; compiler can optimize.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/data.c b/src/data.c
index 0754d4c176d..7a8179ed38d 100644
--- a/src/data.c
+++ b/src/data.c
@@ -2775,6 +2775,9 @@ enum arithop
     Alogxor
   };
 
+enum { FIXNUMS_FIT_IN_LONG = (LONG_MIN <= MOST_NEGATIVE_FIXNUM
+                              && MOST_POSITIVE_FIXNUM <= LONG_MAX) };
+
 static void
 free_mpz_value (void *value_ptr)
 {
@@ -2829,7 +2832,7 @@ arith_driver (enum arithop code, ptrdiff_t nargs, Lisp_Object *args)
         case Aadd:
           if (BIGNUMP (val))
             mpz_add (accum, accum, XBIGNUM (val)->value);
-          else if (sizeof (EMACS_INT) > sizeof (long))
+          else if (! FIXNUMS_FIT_IN_LONG)
             {
               mpz_t tem;
               mpz_init (tem);
@@ -2854,7 +2857,7 @@ arith_driver (enum arithop code, ptrdiff_t nargs, Lisp_Object *args)
             }
           else if (BIGNUMP (val))
             mpz_sub (accum, accum, XBIGNUM (val)->value);
-          else if (sizeof (EMACS_INT) > sizeof (long))
+          else if (! FIXNUMS_FIT_IN_LONG)
             {
               mpz_t tem;
               mpz_init (tem);
@@ -2870,7 +2873,7 @@ arith_driver (enum arithop code, ptrdiff_t nargs, Lisp_Object *args)
         case Amult:
           if (BIGNUMP (val))
             mpz_mul (accum, accum, XBIGNUM (val)->value);
-          else if (sizeof (EMACS_INT) > sizeof (long))
+          else if (! FIXNUMS_FIT_IN_LONG)
             {
               mpz_t tem;
               mpz_init (tem);