From 65857caee8ccfac5007a9fd0e5f18cce5e5fe934 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Wed, 9 Mar 2022 18:48:52 -0500 Subject: [PATCH] libstdc++: Avoid implicit narrowing from uint128_t [PR104859] We need to be explicit about narrowing conversions from uint128_t since, on targets that lack __int128, this type is defined as an integer-class type that is only _explicitly_ convertible to the builtin integer types. This issue was latent until r12-7563-ge32869a17b788b made the frontend correctly reject explicit conversion functions during (dependent) copy-initialization. PR libstdc++/104859 libstdc++-v3/ChangeLog: * src/c++17/floating_to_chars.cc (__floating_to_chars_hex): Be explicit when narrowing the shifted effective_mantissa, since it may have an integer-class type. --- libstdc++-v3/src/c++17/floating_to_chars.cc | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/libstdc++-v3/src/c++17/floating_to_chars.cc b/libstdc++-v3/src/c++17/floating_to_chars.cc index 5825e66..66bd457 100644 --- a/libstdc++-v3/src/c++17/floating_to_chars.cc +++ b/libstdc++-v3/src/c++17/floating_to_chars.cc @@ -801,14 +801,14 @@ template char leading_hexit; if constexpr (has_implicit_leading_bit) { - const unsigned nibble = effective_mantissa >> rounded_mantissa_bits; + const auto nibble = unsigned(effective_mantissa >> rounded_mantissa_bits); __glibcxx_assert(nibble <= 2); leading_hexit = '0' + nibble; effective_mantissa &= ~(mantissa_t{0b11} << rounded_mantissa_bits); } else { - const unsigned nibble = effective_mantissa >> (rounded_mantissa_bits-4); + const auto nibble = unsigned(effective_mantissa >> (rounded_mantissa_bits-4)); __glibcxx_assert(nibble < 16); leading_hexit = "0123456789abcdef"[nibble]; effective_mantissa &= ~(mantissa_t{0b1111} << (rounded_mantissa_bits-4)); @@ -853,7 +853,7 @@ template while (effective_mantissa != 0) { nibble_offset -= 4; - const unsigned nibble = effective_mantissa >> nibble_offset; + const auto nibble = unsigned(effective_mantissa >> nibble_offset); __glibcxx_assert(nibble < 16); *first++ = "0123456789abcdef"[nibble]; ++written_hexits; -- 2.7.4