* [committed] libstdc++: Fix constexpr functions to conform to older standards
@ 2023-08-09 14:22 Jonathan Wakely
0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2023-08-09 14:22 UTC (permalink / raw)
To: libstdc++, gcc-patches
Tested x86_64-linux. Pushed to trunk.
-- >8 --
Some constexpr functions were inadvertently relying on relaxed constexpr
rules from later standards.
libstdc++-v3/ChangeLog:
* include/bits/chrono.h (duration_cast): Do not use braces
around statements for C++11 constexpr rules.
* include/bits/stl_algobase.h (__lg): Rewrite as a single
statement for C++11 constexpr rules.
* include/experimental/bits/fs_path.h (path::string): Use
_GLIBCXX17_CONSTEXPR not _GLIBCXX_CONSTEXPR for 'if constexpr'.
* include/std/charconv (__to_chars_8): Initialize variable for
C++17 constexpr rules.
---
libstdc++-v3/include/bits/chrono.h | 6 ++++--
libstdc++-v3/include/bits/stl_algobase.h | 15 ++++++---------
libstdc++-v3/include/experimental/bits/fs_path.h | 2 +-
libstdc++-v3/include/std/charconv | 2 +-
4 files changed, 12 insertions(+), 13 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono.h b/libstdc++-v3/include/bits/chrono.h
index e9490767c56..b2713d57ef1 100644
--- a/libstdc++-v3/include/bits/chrono.h
+++ b/libstdc++-v3/include/bits/chrono.h
@@ -276,8 +276,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if constexpr (is_same_v<_ToDur, duration<_Rep, _Period>>)
return __d;
else
+ {
#endif
- {
using __to_period = typename _ToDur::period;
using __to_rep = typename _ToDur::rep;
using __cf = ratio_divide<_Period, __to_period>;
@@ -285,7 +285,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using __dc = __duration_cast_impl<_ToDur, __cf, __cr,
__cf::num == 1, __cf::den == 1>;
return __dc::__cast(__d);
- }
+#if __cpp_inline_variables && __cpp_if_constexpr
+ }
+#endif
}
/** Trait indicating whether to treat a type as a floating-point type.
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index dd95e94f7e9..2037d6c0443 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -1518,15 +1518,12 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
return std::__bit_width(make_unsigned_t<_Tp>(__n)) - 1;
#else
// Use +__n so it promotes to at least int.
- const int __sz = sizeof(+__n);
- int __w = __sz * __CHAR_BIT__ - 1;
- if (__sz == sizeof(long long))
- __w -= __builtin_clzll(+__n);
- else if (__sz == sizeof(long))
- __w -= __builtin_clzl(+__n);
- else if (__sz == sizeof(int))
- __w -= __builtin_clz(+__n);
- return __w;
+ return (sizeof(+__n) * __CHAR_BIT__ - 1)
+ - (sizeof(+__n) == sizeof(long long)
+ ? __builtin_clzll(+__n)
+ : (sizeof(+__n) == sizeof(long)
+ ? __builtin_clzl(+__n)
+ : __builtin_clz(+__n)));
#endif
}
diff --git a/libstdc++-v3/include/experimental/bits/fs_path.h b/libstdc++-v3/include/experimental/bits/fs_path.h
index e0e47188bb9..bf07754fd84 100644
--- a/libstdc++-v3/include/experimental/bits/fs_path.h
+++ b/libstdc++-v3/include/experimental/bits/fs_path.h
@@ -1042,7 +1042,7 @@ namespace __detail
inline std::basic_string<_CharT, _Traits, _Allocator>
path::string(const _Allocator& __a) const
{
- if _GLIBCXX_CONSTEXPR (is_same<_CharT, value_type>::value)
+ if _GLIBCXX17_CONSTEXPR (is_same<_CharT, value_type>::value)
return { _M_pathname.begin(), _M_pathname.end(), __a };
using _WString = basic_string<_CharT, _Traits, _Allocator>;
diff --git a/libstdc++-v3/include/std/charconv b/libstdc++-v3/include/std/charconv
index b34d672f5bd..cf2b1161014 100644
--- a/libstdc++-v3/include/std/charconv
+++ b/libstdc++-v3/include/std/charconv
@@ -242,7 +242,7 @@ namespace __detail
static_assert(__integer_to_chars_is_unsigned<_Tp>, "implementation bug");
to_chars_result __res;
- unsigned __len;
+ unsigned __len = 0;
if _GLIBCXX17_CONSTEXPR (__gnu_cxx::__int_traits<_Tp>::__digits <= 16)
{
--
2.41.0
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