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libstdc++: Fix <charconv> uses of signed types with <bit> functions 

In <charconv> we pass the int __base parameter to our internal versions
of <bit> functions, __bit_width and __countr_zero. Those functions are
only defined for unsigned types, so we need to convert the base to
unsigned. The base must be in the range [2,36] so we can mask off the
low bits and then convert that to unsigned, so that we don't need to
care about negative values becoming large unsigned values.

libstdc++-v3/ChangeLog:

	* include/std/charconv (__from_chars_pow2_base): Convert base to
	unsigned for call to __countr_zero.
	(__from_chars_alnum): Likewise for call to __bit_width.
This commit is contained in:
Jonathan Wakely 2023-11-14 10:56:57 +00:00
parent 6f2fc42d9e
commit 1c15303375
1 changed files with 3 additions and 3 deletions
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6
libstdc++-v3/include/std/charconv
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@ -465,7 +465,7 @@ namespace __detail
// __glibcxx_assert((__base & (__base - 1)) == 0);
// __glibcxx_assert(_DecOnly ? __base <= 8 : __base <= 32);
const int __log2_base = __countr_zero(__base);
const int __log2_base = __countr_zero(unsigned(__base & 0x3f));
const ptrdiff_t __len = __last - __first;
ptrdiff_t __i = 0;
@ -517,9 +517,9 @@ namespace __detail
__from_chars_alnum(const char*& __first, const char* __last, _Tp& __val,
int __base)
{
// __glibcxx_assert(!_DecOnly || __base <= 10);
// __glibcxx_assert(_DecOnly ? __base <= 10 : __base <= 36);
const int __bits_per_digit = __bit_width(__base);
const int __bits_per_digit = __bit_width(unsigned(__base & 0x3f));
int __unused_bits_lower_bound = __gnu_cxx::__int_traits<_Tp>::__digits;
for (; __first != __last; ++__first)
{