diff options
Diffstat (limited to 'libcpp/expr.cc')
| -rw-r--r-- | libcpp/expr.cc | 28 |
1 files changed, 23 insertions, 5 deletions
diff --git a/libcpp/expr.cc b/libcpp/expr.cc index 4573752..7bb57a3 100644 --- a/libcpp/expr.cc +++ b/libcpp/expr.cc @@ -53,7 +53,7 @@ static cpp_num num_equality_op (cpp_reader *, cpp_num, cpp_num, static cpp_num num_mul (cpp_reader *, cpp_num, cpp_num); static cpp_num num_div_op (cpp_reader *, cpp_num, cpp_num, enum cpp_ttype, location_t); -static cpp_num num_lshift (cpp_num, size_t, size_t); +static cpp_num num_lshift (cpp_reader *, cpp_num, size_t, size_t); static cpp_num num_rshift (cpp_num, size_t, size_t); static cpp_num append_digit (cpp_num, int, int, size_t); @@ -2049,7 +2049,7 @@ num_rshift (cpp_num num, size_t precision, size_t n) /* Shift NUM, of width PRECISION, left by N bits. */ static cpp_num -num_lshift (cpp_num num, size_t precision, size_t n) +num_lshift (cpp_reader *pfile, cpp_num num, size_t precision, size_t n) { if (n >= precision) { @@ -2075,8 +2075,26 @@ num_lshift (cpp_num num, size_t precision, size_t n) } num = num_trim (num, precision); - if (num.unsignedp) + if (num.unsignedp + /* For C++20 or later since P1236R1, there is no overflow for signed + left shifts, it is as if the shift was in uintmax_t and cast + back to intmax_t afterwards. */ + || (CPP_OPTION (pfile, cplusplus) + && CPP_OPTION (pfile, lang) >= CLK_GNUCXX20)) num.overflow = false; + else if (CPP_OPTION (pfile, cplusplus) + && CPP_OPTION (pfile, lang) >= CLK_GNUCXX11 + && num_positive (orig, precision)) + { + /* For C++11 - C++17 since CWG1457, 1 << 63 is allowed because it is + representable in uintmax_t, but 3 << 63 is not. + Test whether num >> (precision - 1 - n) as logical + shift is > 1. */ + maybe_orig = orig; + maybe_orig.unsignedp = true; + maybe_orig = num_rshift (maybe_orig, precision, precision - 1 - n); + num.overflow = maybe_orig.high || maybe_orig.low > 1; + } else { maybe_orig = num_rshift (num, precision, n); @@ -2149,7 +2167,7 @@ num_binary_op (cpp_reader *pfile, cpp_num lhs, cpp_num rhs, enum cpp_ttype op) else n = rhs.low; if (op == CPP_LSHIFT) - lhs = num_lshift (lhs, precision, n); + lhs = num_lshift (pfile, lhs, precision, n); else lhs = num_rshift (lhs, precision, n); break; @@ -2347,7 +2365,7 @@ num_div_op (cpp_reader *pfile, cpp_num lhs, cpp_num rhs, enum cpp_ttype op, rhs.unsignedp = true; lhs.unsignedp = true; i = precision - i - 1; - sub = num_lshift (rhs, precision, i); + sub = num_lshift (pfile, rhs, precision, i); result.high = result.low = 0; for (;;) |