Fixed close handles with Alpine and MUSL

include/boost/process/v2/posix/detail/close_handles.ipp

@@ -14,7 +14,9 @@
 #include <boost/process/v2/detail/config.hpp>
 #include <boost/process/v2/detail/last_error.hpp>
 #include <boost/process/v2/posix/detail/close_handles.hpp>
-// linux has close_range since 5.19
+// linux has close_range since 5.9
+// see: https://man.archlinux.org/man/close_range.2.en#HISTORY
+//      https://elixir.bootlin.com/linux/v5.9/source/fs/open.c#L1318
 
 
 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__)
@@ -31,7 +33,7 @@
 #include <unistd.h>
 #define BOOST_PROCESS_V2_HAS_CLOSE_RANGE_AND_CLOSEFROM 1 
 
-#elif defined(__sun)
+#elif defined(__sun) // if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__)
 
 /*https://docs.oracle.com/cd/E36784_01/html/E36874/closefrom-3c.html
 
@@ -41,22 +43,44 @@ int fdwalk(int (*func)(void *, int), void *cd);
 #include <stdlib.h>
 #define BOOST_PROCESS_V2_HAS_PDFORK 1 
 
-#elif defined(__linux__)
+#elif defined(__linux__) // elif defined(__sun)
 
-#include <linux/version.h>
+// define BOOST_PROCESS_V2_POSIX_FORCE_DISABLE_CLOSE_RANGE to force disable any usage of ::close_range()
+
+
+#include <sys/syscall.h>
+
+// All checks here are intended to check whether target system has ::close_range()
+// Note that this checks only valid on glibc. MUSL doens't have ::close_range() anyway. So we don't care about any
+// MUSL library macroses
+#if defined(__GLIBC__)
+
+// On glibc we also must have ::close_range() wrapper around system call.
+// If we're building on system with new kernel, BUT without this wrapper (old glibc) the build will be failed
+#include <gnu/libc-version.h>
+#if (__GLIBC__ >= 2 && __GLIBC_MINOR__ >= 34) && !defined(BOOST_PROCESS_V2_POSIX_FORCE_DISABLE_CLOSE_RANGE)
+#define BOOST_PROCESS_V2_HAS_CLOSE_RANGE 1
+#endif // __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 34
+
+#endif // ifdef __GLIBC__
+
+// glibc version doesn't meet version requirements or we're building with MUSL.
+// Just try to check linux version code. If system call is supported we'll use raw system call
+#if !defined(BOOST_PROCESS_V2_HAS_CLOSE_RANGE) && defined(SYS_close_range) && !defined(BOOST_PROCESS_V2_POSIX_FORCE_DISABLE_CLOSE_RANGE)
+#define BOOST_PROCESS_V2_HAS_CLOSE_RANGE_SYSCALL 1
+#endif // if !defined(BOOST_PROCESS_V2_HAS_CLOSE_RANGE) && LINUX_VERSION_CODE >= KERNEL_VERSION(5,9,0)
 
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,11,0)
 
 // https://man7.org/linux/man-pages/man2/close_range.2.html
+#if defined(BOOST_PROCESS_V2_HAS_CLOSE_RANGE) || defined(BOOST_PROCESS_V2_HAS_CLOSE_RANGE_SYSCALL)
 #include <linux/close_range.h>
-#define BOOST_PROCESS_V2_HAS_CLOSE_RANGE 1 
-#else 
+#include <sys/syscall.h>
 
+#else // ifdef BOOST_PROCESS_V2_HAS_CLOSE_RANGE || defined(BOOST_PROCESS_V2_HAS_CLOSE_RANGE_SYSCALL)
 #include <dirent.h>
+#endif // BOOST_PROCESS_V2_HAS_CLOSE_RANGE || defined(BOOST_PROCESS_V2_HAS_CLOSE_RANGE_SYSCALL)
 
-#endif
-
-#else
+#else // elif defined(__linux__)
 
 #include <dirent.h>
 
@@ -145,6 +169,36 @@ void close_all(const std::vector<int> & whitelist, error_code & ec)
         ::close_range(0, std::numeric_limits<int>::max(), CLOSE_RANGE_UNSHARE);
 }
 
+#elif defined(BOOST_PROCESS_V2_HAS_CLOSE_RANGE_SYSCALL)
+
+// linux impl - whitelist must be ordered
+void close_all(const std::vector<int> & whitelist, error_code & ec)
+{
+    // https://patchwork.kernel.org/project/linux-fsdevel/cover/[email protected]/
+    //the most common scenario is whitelist = {0,1,2}
+    if (!whitelist.empty())
+    {
+        if (whitelist.front() != 0)
+            ::syscall(SYS_close_range, 0, whitelist.front() - 1, CLOSE_RANGE_UNSHARE);
+
+        for (std::size_t idx = 0u;
+             idx < (whitelist.size() - 1u);
+             idx++)
+        {
+            const auto mine = whitelist[idx];
+            const auto next = whitelist[idx + 1];
+            if ((mine + 1) != next && (mine != next))
+            {
+                ::syscall(SYS_close_range, mine + 1, next - 1, CLOSE_RANGE_UNSHARE);
+            }
+        }
+
+        ::syscall(SYS_close_range, whitelist.back() + 1, std::numeric_limits<int>::max(), CLOSE_RANGE_UNSHARE);
+    }
+    else
+        ::syscall(SYS_close_range, 0, std::numeric_limits<int>::max(), CLOSE_RANGE_UNSHARE);
+}
+
 #else
 
 // default one
@@ -191,4 +245,4 @@ void close_all(const std::vector<int> & whitelist, error_code & ec)
 
 BOOST_PROCESS_V2_END_NAMESPACE
 
-#endif //BOOST_PROCESS_V2_POSIX_DETAIL_CLOSE_HANDLES_IPP
+#endif //BOOST_PROCESS_V2_POSIX_DETAIL_CLOSE_HANDLES_IPP