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* [gcc r11-9798] libstdc++: Avoid implicit narrowing from uint128_t [PR104859]
@ 2022-04-07 19:36 Patrick Palka
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From: Patrick Palka @ 2022-04-07 19:36 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:c859c99a85b8743b2c1edc097c6f6406de337f45
commit r11-9798-gc859c99a85b8743b2c1edc097c6f6406de337f45
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Mar 9 18:48:52 2022 -0500
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.
(cherry picked from commit 65857caee8ccfac5007a9fd0e5f18cce5e5fe934)
Diff:
---
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 44f547a77b4..2545022ced6 100644
--- a/libstdc++-v3/src/c++17/floating_to_chars.cc
+++ b/libstdc++-v3/src/c++17/floating_to_chars.cc
@@ -799,14 +799,14 @@ template<typename T>
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));
@@ -847,7 +847,7 @@ template<typename T>
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;
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