[lldb] Move once_flags in HostInfoLinux so the internal state struct

[teemperor]

Summary

The HostInfoLinuxFields struct is supposed to be set up/torn down on Initialize/Terminate
and should contain all the state of the plugin. once_flags are part of this state and should
also be reset on Terminate so we can re-initialize these lazy values after the next
Initialize call.

This itself is NFC as the HostInfoLinux was broken before this patch and is still broken
afterwards. D104091 will be the proper fix.

[vitalybuka]

lldb/source/Host/linux/HostInfoLinux.cpp

41

this still does not solve memory leak if HostInfoLinux::Initialize called twice

[vitalybuka]

I see comment on the D104091

lldb/source/Host/linux/HostInfoLinux.cpp

 //===-- HostInfoLinux.cpp -------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Host/linux/HostInfoLinux.h"
 #include "lldb/Host/Config.h"
 #include "lldb/Host/FileSystem.h"
 #include "lldb/Utility/Log.h"
 
 #include "llvm/Support/Threading.h"
 
 #include <climits>
 #include <cstdio>
 #include <cstring>
 #include <sys/utsname.h>
 #include <unistd.h>
 
 #include <algorithm>
 #include <mutex>
 
 using namespace lldb_private;
 
 namespace {
 struct HostInfoLinuxFields {
+  llvm::once_flag m_distribution_once_flag;
   std::string m_distribution_id;
+  llvm::once_flag m_os_version_once_flag;
   llvm::VersionTuple m_os_version;
 };
 
 HostInfoLinuxFields *g_fields = nullptr;
 }
 
 void HostInfoLinux::Initialize(SharedLibraryDirectoryHelper *helper) {
   HostInfoPosix::Initialize(helper);
 
   g_fields = new HostInfoLinuxFields();
 }
 
 llvm::VersionTuple HostInfoLinux::GetOSVersion() {
-  static llvm::once_flag g_once_flag;
-  llvm::call_once(g_once_flag, []() {
+  assert(g_fields && "Missing call to Initialize?");
+  llvm::call_once(g_fields->m_os_version_once_flag, []() {
     struct utsname un;
     if (uname(&un) != 0)
       return;
 
     llvm::StringRef release = un.release;
     // The kernel release string can include a lot of stuff (e.g.
     // 4.9.0-6-amd64). We're only interested in the numbered prefix.
     release = release.substr(0, release.find_first_not_of("0123456789."));
bool HostInfoLinux::GetOSKernelDescription(std::string &s) {
   if (uname(&un) < 0)
     return false;
 
   s.assign(un.version);
   return true;
 }
 
 llvm::StringRef HostInfoLinux::GetDistributionId() {
+  assert(g_fields && "Missing call to Initialize?");
   // Try to run 'lbs_release -i', and use that response for the distribution
   // id.
-  static llvm::once_flag g_once_flag;
-  llvm::call_once(g_once_flag, []() {
+  llvm::call_once(g_fields->m_distribution_once_flag, []() {
 
     Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST));
     LLDB_LOGF(log, "attempting to determine Linux distribution...");
 
     // check if the lsb_release command exists at one of the following paths
     const char *const exe_paths[] = {"/bin/lsb_release",
                                      "/usr/bin/lsb_release"};
 
     for (size_t exe_index = 0;