[libc++] Remove sysctl-based implementation of thread::hardware_concurrency()
Using sysctl requires including headers that are considered internal on
Linux, like <sys/sysctl.h> & friends. Instead, sysconf is defined by POSIX
(and we have a fallback for Windows), so all the systems we support should
be happy with just sysconf.
Differential Revision: https://reviews.llvm.org/D92135
GitOrigin-RevId: 3d7f19ff182b249521061cff7a908efbc68d9f54
diff --git a/src/thread.cpp b/src/thread.cpp
index e1dc972..5959d8b 100644
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -15,20 +15,8 @@
#include "future"
#include "limits"
-#if __has_include(<sys/types.h>)
-# include <sys/types.h>
-#endif
-
-#if __has_include(<sys/param.h>)
-# include <sys/param.h>
-#endif
-
-#if __has_include(<sys/sysctl.h>)
-# include <sys/sysctl.h>
-#endif
-
#if __has_include(<unistd.h>)
-# include <unistd.h>
+# include <unistd.h> // for sysconf
#endif
#if defined(__NetBSD__)
@@ -84,13 +72,7 @@
unsigned
thread::hardware_concurrency() _NOEXCEPT
{
-#if defined(CTL_HW) && defined(HW_NCPU)
- unsigned n;
- int mib[2] = {CTL_HW, HW_NCPU};
- std::size_t s = sizeof(n);
- sysctl(mib, 2, &n, &s, 0, 0);
- return n;
-#elif defined(_SC_NPROCESSORS_ONLN)
+#if defined(_SC_NPROCESSORS_ONLN)
long result = sysconf(_SC_NPROCESSORS_ONLN);
// sysconf returns -1 if the name is invalid, the option does not exist or
// does not have a definite limit.