return *non_constant_p;
}
+/* Check whether the shift operation with code CODE and type TYPE on LHS
+ and RHS is undefined. If it is, give an error with an explanation,
+ and return true; return false otherwise. */
+
+static bool
+cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx,
+ enum tree_code code, tree type, tree lhs, tree rhs)
+{
+ if ((code != LSHIFT_EXPR && code != RSHIFT_EXPR)
+ || TREE_CODE (lhs) != INTEGER_CST
+ || TREE_CODE (rhs) != INTEGER_CST)
+ return false;
+
+ tree lhstype = TREE_TYPE (lhs);
+ unsigned HOST_WIDE_INT uprec = TYPE_PRECISION (TREE_TYPE (lhs));
+
+ /* [expr.shift] The behavior is undefined if the right operand
+ is negative, or greater than or equal to the length in bits
+ of the promoted left operand. */
+ if (tree_int_cst_sgn (rhs) == -1)
+ {
+ if (!ctx->quiet)
+ error_at (loc, "right operand of shift expression %q+E is negative",
+ build2_loc (loc, code, type, lhs, rhs));
+ return true;
+ }
+ if (compare_tree_int (rhs, uprec) >= 0)
+ {
+ if (!ctx->quiet)
+ error_at (loc, "right operand of shift expression %q+E is >= than "
+ "the precision of the left operand",
+ build2_loc (loc, code, type, lhs, rhs));
+ return true;
+ }
+
+ /* The value of E1 << E2 is E1 left-shifted E2 bit positions; [...]
+ if E1 has a signed type and non-negative value, and E1x2^E2 is
+ representable in the corresponding unsigned type of the result type,
+ then that value, converted to the result type, is the resulting value;
+ otherwise, the behavior is undefined. */
+ if (code == LSHIFT_EXPR && !TYPE_UNSIGNED (lhstype)
+ && (cxx_dialect >= cxx11))
+ {
+ if (tree_int_cst_sgn (lhs) == -1)
+ {
+ if (!ctx->quiet)
+ error_at (loc, "left operand of shift expression %q+E is negative",
+ build2_loc (loc, code, type, lhs, rhs));
+ return true;
+ }
+ /* For signed x << y the following:
+ (unsigned) x >> ((prec (lhs) - 1) - y)
+ if > 1, is undefined. The right-hand side of this formula
+ is the highest bit of the LHS that can be set (starting from 0),
+ so that the shift doesn't overflow. We then right-shift the LHS
+ to see whether any other bit is set making the original shift
+ undefined -- the result is not representable in the corresponding
+ unsigned type. */
+ tree t = build_int_cst (unsigned_type_node, uprec - 1);
+ t = fold_build2 (MINUS_EXPR, unsigned_type_node, t, rhs);
+ tree ulhs = fold_convert (unsigned_type_for (lhstype), lhs);
+ t = fold_build2 (RSHIFT_EXPR, TREE_TYPE (ulhs), ulhs, t);
+ if (tree_int_cst_lt (integer_one_node, t))
+ {
+ if (!ctx->quiet)
+ error_at (loc, "shift expression %q+E overflows",
+ build2_loc (loc, code, type, lhs, rhs));
+ return true;
+ }
+ }
+ return false;
+}
+
/* Subroutine of cxx_eval_constant_expression.
Attempt to reduce the unary expression tree T to a compile time value.
If successful, return the value. Otherwise issue a diagnostic
else
r = build2_loc (loc, code, type, lhs, rhs);
}
+ else if (cxx_eval_check_shift_p (loc, ctx, code, type, lhs, rhs))
+ *non_constant_p = true;
VERIFY_CONSTANT (r);
return r;
}
--- /dev/null
+// { dg-do compile { target c++11 } }
+
+constexpr int
+fn1 (int i, int j)
+{
+ return i << j; // { dg-error "is negative" }
+}
+
+constexpr int i1 = fn1 (1, -1);
+
+constexpr int
+fn2 (int i, int j)
+{
+ return i << j; // { dg-error "is >= than the precision of the left operand" }
+}
+
+constexpr int i2 = fn2 (1, 200);
+
+constexpr int
+fn3 (int i, int j)
+{
+ return i << j; // { dg-error "is negative" }
+}
+
+constexpr int i3 = fn3 (-1, 2);
+
+constexpr int
+fn4 (int i, int j)
+{
+ return i << j; // { dg-error "overflows" }
+}
+
+constexpr int i4 = fn4 (__INT_MAX__, 2);
+
+constexpr int
+fn5 (int i, int j)
+{
+ return i << j;
+}
+
+constexpr int i5 = fn5 (__INT_MAX__, 1);
+
+constexpr int
+fn6 (unsigned int i, unsigned int j)
+{
+ return i << j; // { dg-error "is >= than the precision of the left operand" }
+}
+
+constexpr int i6 = fn6 (1, -1);
+
+constexpr int
+fn7 (int i, int j)
+{
+ return i >> j; // { dg-error "is negative" }
+}
+
+constexpr int i7 = fn7 (1, -1);
+
+constexpr int
+fn8 (int i, int j)
+{
+ return i >> j;
+}
+
+constexpr int i8 = fn8 (-1, 1);
+
+constexpr int
+fn9 (int i, int j)
+{
+ return i >> j; // { dg-error "is >= than the precision of the left operand" }
+}
+
+constexpr int i9 = fn9 (1, 200);
}
constexpr int i1 = fn1 (5, 3);
-constexpr int i2 = fn1 (5, -2);
-constexpr int i3 = fn1 (5, sizeof (int) * __CHAR_BIT__);
-constexpr int i4 = fn1 (5, 256);
+constexpr int i2 = fn1 (5, -2); // { dg-error "is negative" }
+constexpr int i3 = fn1 (5, sizeof (int) * __CHAR_BIT__); // { dg-error "is >= than the precision of the left operand" }
+constexpr int i4 = fn1 (5, 256); // { dg-error "is >= than the precision of the left operand" }
constexpr int i5 = fn1 (5, 2);
-constexpr int i6 = fn1 (-2, 4);
+constexpr int i6 = fn1 (-2, 4); // { dg-error "is negative" }
constexpr int i7 = fn1 (0, 2);
SA (i1 == 40);
}
constexpr int j1 = fn2 (4, 1);
-constexpr int j2 = fn2 (4, -1);
-constexpr int j3 = fn2 (10, sizeof (int) * __CHAR_BIT__);
-constexpr int j4 = fn2 (1, 256);
+constexpr int j2 = fn2 (4, -1); // { dg-error "is negative" }
+constexpr int j3 = fn2 (10, sizeof (int) * __CHAR_BIT__); // { dg-error "is >= than the precision of the left operand" }
+constexpr int j4 = fn2 (1, 256); // { dg-error "is >= than the precision of the left operand" }
constexpr int j5 = fn2 (5, 2);
constexpr int j6 = fn2 (-2, 4);
constexpr int j7 = fn2 (0, 4);
projects / gcc.git / commitdiff