[lldb] Replace std::once_flag with llvm::once_flag.

[davide]

Summary

The former seems like it's not working on some platforms.
All the other uses use llvm::, so, let's change for consistency.

[davide]

I and Jason discussed this offline and he's fine with it, so, I'm going to land this now.

[mgorny]

This broke NetBSD buildbot: http://lab.llvm.org:8011/builders/netbsd-amd64/builds/21974

FAILED: tools/lldb/source/Target/CMakeFiles/lldbTarget.dir/Process.cpp.o 
/usr/bin/g++  -DGTEST_HAS_RTTI=0 -DHAVE_ROUND -DLIBXML2_DEFINED -DLLDB_CONFIGURATION_RELEASE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools/lldb/source/Target -I/home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target -Itools/lldb/source -I/home/motus/netbsd8/netbsd8/llvm/tools/lldb/include -Itools/lldb/include -Iinclude -I/home/motus/netbsd8/netbsd8/llvm/include -I/usr/pkg/include/python2.7 -I/home/motus/netbsd8/netbsd8/llvm/tools/clang/include -Itools/lldb/../clang/include -I/usr/pkg/include/libxml2 -I/home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/. -fPIC -fvisibility-inlines-hidden -Werror=date-time -std=c++14 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wno-maybe-uninitialized -Wdelete-non-virtual-dtor -Wno-comment -fdiagnostics-color -ffunction-sections -fdata-sections -Wno-deprecated-declarations -Wno-unknown-pragmas -Wno-strict-aliasing -Wno-deprecated-register -Wno-vla-extension -O3 -DNDEBUG    -fno-exceptions -fno-rtti -MD -MT tools/lldb/source/Target/CMakeFiles/lldbTarget.dir/Process.cpp.o -MF tools/lldb/source/Target/CMakeFiles/lldbTarget.dir/Process.cpp.o.d -o tools/lldb/source/Target/CMakeFiles/lldbTarget.dir/Process.cpp.o -c /home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target/Process.cpp
/home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target/Process.cpp: In member function 'lldb_private::UtilityFunction* lldb_private::Process::GetLoadImageUtilityFunction(lldb_private::Platform*, llvm::function_ref<std::unique_ptr<lldb_private::UtilityFunction>()>)':
/home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target/Process.cpp:5969:63: error: no matching function for call to 'call_once(llvm::once_flag&, lldb_private::Process::GetLoadImageUtilityFunction(lldb_private::Platform*, llvm::function_ref<std::unique_ptr<lldb_private::UtilityFunction>()>)::<lambda()>)'
                  [&] { m_dlopen_utility_func_up = factory(); });
                                                               ^
In file included from /home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target/Process.cpp:11:0:
/usr/include/g++/mutex:723:5: note: candidate: template<class _Callable, class ... _Args> void std::call_once(std::once_flag&, _Callable&&, _Args&& ...)
     call_once(once_flag& __once, _Callable&& __f, _Args&&... __args)
     ^
/usr/include/g++/mutex:723:5: note:   template argument deduction/substitution failed:
/home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target/Process.cpp:5968:18: note:   cannot convert '((lldb_private::Process*)this)->lldb_private::Process::m_dlopen_utility_func_flag_once' (type 'llvm::once_flag') to type 'std::once_flag&'
   std::call_once(m_dlopen_utility_func_flag_once,
                  ^
/home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target/Process.cpp: In member function 'void lldb_private::Process::PrintWarning(__uint64_t, const void*, const char*, ...)':
/home/motus/netbsd8/netbsd8/llvm/tools/lldb/source/Target/Process.cpp:5687:24: warning: second parameter of 'va_start' not last named argument [-Wvarargs]
     va_start(args, fmt);
                        ^

[mgorny]

Unless I'm mistaken, this is fixed by replacing std::call_once with llvm::call_once. I'll complete testing and commit it later today.

[krytarowski]

This breaks NetBSD as it shall be paired with llvm::call_once.

lldb/trunk/include/lldb/Target/Process.h

 #include "lldb/Utility/ProcessInfo.h"
 #include "lldb/Utility/Status.h"
 #include "lldb/Utility/StructuredData.h"
 #include "lldb/Utility/TraceOptions.h"
 #include "lldb/Utility/UserIDResolver.h"
 #include "lldb/lldb-private.h"
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/Threading.h"
 #include "llvm/Support/VersionTuple.h"
 
 namespace lldb_private {
 
 template <typename B, typename S> struct Range;
 
 // ProcessProperties
 class ProcessProperties : public Properties {
protected:
   WarningsCollection m_warnings_issued; // A set of object pointers which have
                                         // already had warnings printed
   std::mutex m_run_thread_plan_lock;
   StructuredDataPluginMap m_structured_data_plugin_map;
 
   enum { eCanJITDontKnow = 0, eCanJITYes, eCanJITNo } m_can_jit;
   
   std::unique_ptr<UtilityFunction> m_dlopen_utility_func_up;
-  std::once_flag m_dlopen_utility_func_flag_once;
+  llvm::once_flag m_dlopen_utility_func_flag_once;
 
   size_t RemoveBreakpointOpcodesFromBuffer(lldb::addr_t addr, size_t size,
                                            uint8_t *buf) const;
 
   void SynchronouslyNotifyStateChanged(lldb::StateType state);
 
   void SetPublicState(lldb::StateType new_state, bool restarted);
 

lldb/trunk/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp

 static os_activity_stream_for_pid_t s_os_activity_stream_for_pid;
 static os_activity_stream_resume_t s_os_activity_stream_resume;
 static os_activity_stream_cancel_t s_os_activity_stream_cancel;
 static os_log_copy_formatted_message_t s_os_log_copy_formatted_message;
 static os_activity_stream_set_event_handler_t
     s_os_activity_stream_set_event_handler;
 
 bool LookupSPICalls() {
-  static std::once_flag s_once_flag;
+  static llvm::once_flag s_once_flag;
   static bool s_has_spi;
 
   std::call_once(s_once_flag, [] {
     dlopen ("/System/Library/PrivateFrameworks/LoggingSupport.framework/LoggingSupport", RTLD_NOW);
     s_os_activity_stream_for_pid = (os_activity_stream_for_pid_t)dlsym(
         RTLD_DEFAULT, "os_activity_stream_for_pid");
     s_os_activity_stream_resume = (os_activity_stream_resume_t)dlsym(
         RTLD_DEFAULT, "os_activity_stream_resume");