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[libc++] Avoid <climits> dependency in <thread> 

The standard guarantees sleep durations of 2^63-1 nanoseconds to work.
Instead of depending on INT64_MAX or ULONGLONG_MAX to exist via the
header pollution, fold the constant directly. That has the additional
positive side effect that it avoids long double arithmetic bugs in GCC.

Differential Revision: https://reviews.llvm.org/D99516
This commit is contained in:
Joerg Sonnenberger 2021-02-18 15:15:53 +01:00
parent ffcb4b43b7
commit 9f4022ffeb
1 changed files with 5 additions and 6 deletions
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11
libcxx/include/thread
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@ -362,12 +362,11 @@ sleep_for(const chrono::duration<_Rep, _Period>& __d)
{
if (__d > chrono::duration<_Rep, _Period>::zero())
{
#if defined(_LIBCPP_COMPILER_GCC) && (__powerpc__ || __POWERPC__)
// GCC's long double const folding is incomplete for IBM128 long doubles.
_LIBCPP_CONSTEXPR chrono::duration<long double> _Max = chrono::duration<long double>(ULLONG_MAX/1000000000ULL) ;
#else
_LIBCPP_CONSTEXPR chrono::duration<long double> _Max = chrono::nanoseconds::max();
#endif
// The standard guarantees a 64bit signed integer resolution for nanoseconds,
// so use INT64_MAX / 1e9 as cut-off point. Use a constant to avoid <climits>
// and issues with long double folding on PowerPC with GCC.
_LIBCPP_CONSTEXPR chrono::duration<long double> _Max =
chrono::duration<long double>(9223372036.0L);
chrono::nanoseconds __ns;
if (__d < _Max)
{