vim-patch:8.1.0990: floating point exception with "%= 0" and "/= 0"

Problem:    Floating point exception with "%= 0" and "/= 0".
Solution:   Avoid dividing by zero. (Dominique Pelle, closes vim/vim#4058)
e21c1580b7

src/nvim/eval.c

@@ -526,6 +526,35 @@ const list_T *eval_msgpack_type_lists[] = {
   [kMPExt] = NULL,
 };
 
+// Return "n1" divided by "n2", taking care of dividing by zero.
+varnumber_T num_divide(varnumber_T n1, varnumber_T n2)
+  FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  varnumber_T result;
+
+  if (n2 == 0) {  // give an error message?
+    if (n1 == 0) {
+      result = VARNUMBER_MIN;  // similar to NaN
+    } else if (n1 < 0) {
+      result = -VARNUMBER_MAX;
+    } else {
+      result = VARNUMBER_MAX;
+    }
+  } else {
+    result = n1 / n2;
+  }
+
+  return result;
+}
+
+// Return "n1" modulus "n2", taking care of dividing by zero.
+varnumber_T num_modulus(varnumber_T n1, varnumber_T n2)
+  FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  // Give an error when n2 is 0?
+  return (n2 == 0) ? 0 : (n1 % n2);
+}
+
 /*
  * Initialize the global and v: variables.
  */
@@ -2047,8 +2076,8 @@ static char_u *ex_let_one(char_u *arg, typval_T *const tv,
               case '+': n = numval + n; break;
               case '-': n = numval - n; break;
               case '*': n = numval * n; break;
-              case '/': n = numval / n; break;
+              case '/': n = num_divide(numval, n); break;
-              case '%': n = numval % n; break;
+              case '%': n = num_modulus(numval, n); break;
             }
           } else if (opt_type == 0 && stringval != NULL) {  // string
             char *const oldstringval = stringval;
@@ -4178,22 +4207,9 @@ static int eval6(char_u **arg, typval_T *rettv, int evaluate, int want_string)
         if (op == '*') {
           n1 = n1 * n2;
         } else if (op == '/') {
-          if (n2 == 0) {                // give an error message?
+          n1 = num_divide(n1, n2);
-            if (n1 == 0) {
-              n1 = VARNUMBER_MIN;  // similar to NaN
-            } else if (n1 < 0) {
-              n1 = -VARNUMBER_MAX;
-            } else {
-              n1 = VARNUMBER_MAX;
-            }
-          } else {
-            n1 = n1 / n2;
-          }
         } else {
-          if (n2 == 0)                  /* give an error message? */
+          n1 = num_modulus(n1, n2);
-            n1 = 0;
-          else
-            n1 = n1 % n2;
         }
         rettv->v_type = VAR_NUMBER;
         rettv->vval.v_number = n1;

src/nvim/eval/executor.c

@@ -74,8 +74,8 @@ int eexe_mod_op(typval_T *const tv1, const typval_T *const tv2,
               case '+': n += tv_get_number(tv2); break;
               case '-': n -= tv_get_number(tv2); break;
               case '*': n *= tv_get_number(tv2); break;
-              case '/': n /= tv_get_number(tv2); break;
+              case '/': n = num_divide(n, tv_get_number(tv2)); break;
-              case '%': n %= tv_get_number(tv2); break;
+              case '%': n = num_modulus(n, tv_get_number(tv2)); break;
             }
             tv_clear(tv1);
             tv1->v_type = VAR_NUMBER;

src/nvim/testdir/test_vimscript.vim

@@ -21,7 +21,7 @@ com! -nargs=1	     Xout     call Xout(<args>)
 "
 " Create a script that consists of the body of the function a:funcname.
 " Replace any ":return" by a ":finish", any argument variable by a global
-" variable, and and every ":call" by a ":source" for the next following argument
+" variable, and every ":call" by a ":source" for the next following argument
 " in the variable argument list.  This function is useful if similar tests are
 " to be made for a ":return" from a function call or a ":finish" in a script
 " file.
@@ -1310,6 +1310,43 @@ func Test_compound_assignment_operators()
     let x .= 'n'
     call assert_equal('2n', x)
 
+    " Test special cases: division or modulus with 0.
+    let x = 1
+    let x /= 0
+    if has('num64')
+        call assert_equal(0x7FFFFFFFFFFFFFFF, x)
+    else
+        call assert_equal(0x7fffffff, x)
+    endif
+
+    let x = -1
+    let x /= 0
+    if has('num64')
+        call assert_equal(-0x7FFFFFFFFFFFFFFF, x)
+    else
+        call assert_equal(-0x7fffffff, x)
+    endif
+
+    let x = 0
+    let x /= 0
+    if has('num64')
+        call assert_equal(-0x7FFFFFFFFFFFFFFF - 1, x)
+    else
+        call assert_equal(-0x7FFFFFFF - 1, x)
+    endif
+
+    let x = 1
+    let x %= 0
+    call assert_equal(0, x)
+
+    let x = -1
+    let x %= 0
+    call assert_equal(0, x)
+
+    let x = 0
+    let x %= 0
+    call assert_equal(0, x)
+
     " Test for string
     let x = 'str'
     let x .= 'ing'