[lldb] Deprecate SBHostOS threading functionality

[bulbazord]

Summary

For some context, Raphael tried to this before: https://reviews.llvm.org/D104231

These methods are not tested at all, and in some cases, are not even fully
implemented (e.g. SBHostOS::ThreadCreated). I'm not convinced it's
possible to use these correctly from Python, and I'm not aware of any
users of these methods. It's difficult to remove these methods
wholesale, but we can start with deprecating them.

A possible follow-up to this change (which may require an RFC to get
more buy in from the community) is to gut these functions entirely. That
is, remove the implementations and replace them either with nothing or
have them dump out a message to stderr saying not to use these.

[JDevlieghere]

LGMT

[clayborg]

I think the SBHostOS::ThreadCreated() function used to just set the thread name for the current thread, but looks like that hasn't been hooked up for a while. Don't know who was using this before, but LGTM.

[JDevlieghere]

lldb/include/lldb/API/SBHostOS.h

28–29

On second thought, I think we should omit the "Do not introduce new uses of this method." This is implied by the fact that it's deprecated.

[bulbazord]

Reword deprecation message

[JDevlieghere]

LGTM

[mib]

LGTM! @bulbazord when you land this, make sure to close @teemperor's diff (D104231). Thanks!

[bulbazord]

In D153900#4469649, @mib wrote:

LGTM! @bulbazord when you land this, make sure to close @teemperor's diff (D104231). Thanks!

👍

lldb/include/lldb/API/SBHostOS.h

public:
   static lldb::SBFileSpec GetProgramFileSpec();
 
   static lldb::SBFileSpec GetLLDBPythonPath();
 
   static lldb::SBFileSpec GetLLDBPath(lldb::PathType path_type);
 
   static lldb::SBFileSpec GetUserHomeDirectory();
 
+  LLDB_DEPRECATED("Threading functionality in SBHostOS is not well supported, "
+                  "not portable, and is difficult to use from Python.")
   static void ThreadCreated(const char *name);
 
+  LLDB_DEPRECATED("Threading functionality in SBHostOS is not well supported, "
+                  "not portable, and is difficult to use from Python.")
   static lldb::thread_t ThreadCreate(const char *name,
                                      lldb::thread_func_t thread_function,
                                      void *thread_arg, lldb::SBError *err);
 
+  LLDB_DEPRECATED("Threading functionality in SBHostOS is not well supported, "
+                  "not portable, and is difficult to use from Python.")
   static bool ThreadCancel(lldb::thread_t thread, lldb::SBError *err);
 
+  LLDB_DEPRECATED("Threading functionality in SBHostOS is not well supported, "
+                  "not portable, and is difficult to use from Python.")
   static bool ThreadDetach(lldb::thread_t thread, lldb::SBError *err);
+
+  LLDB_DEPRECATED("Threading functionality in SBHostOS is not well supported, "
+                  "not portable, and is difficult to use from Python.")
   static bool ThreadJoin(lldb::thread_t thread, lldb::thread_result_t *result,
                          lldb::SBError *err);
 
 private:
 };
 
 } // namespace lldb
 
 #endif // LLDB_API_SBHOSTOS_H

lldb/tools/driver/Driver.cpp

if (error.Fail()) {
     WithColor::error() << "initialization failed: " << error.GetCString()
                        << '\n';
     return 1;
   }
 
   // Setup LLDB signal handlers once the debugger has been initialized.
   SBDebugger::PrintDiagnosticsOnError();
 
-  SBHostOS::ThreadCreated("<lldb.driver.main-thread>");
-
   signal(SIGINT, sigint_handler);
 #if !defined(_WIN32)
   signal(SIGPIPE, SIG_IGN);
   signal(SIGWINCH, sigwinch_handler);
   signal(SIGTSTP, sigtstp_handler);
 #endif
 
   int exit_code = 0;