[lldb] Fix assertion when ScriptedProcess have no pid after launch

This patch should fix an assertion that causes some test failures:
https://ci.swift.org/view/LLDB/job/llvm-org-lldb-release-debuginfo/3587/console

This was caused by the changes introduces in `88f409194d5a` where we
replaced `DidLaunch` by `DidResume` in the `ScriptedProcess` class.

However, by the time we resume the process, the pid should be already
set. To address this, this patch brings back `DidLaunch` which will
initialize the ScriptedProcess pid with a placeholder value. That value
will be updated in `DidResume` to the final pid.

Note, this 2 stage PID initialization is necessary sometimes, when the
scripted process gets stopped at entry (launch) and gets assigned an
object that contains the PID value. In this case, we need to update the
PID when we resume the process after we've stopped at entry.

This also replaces the default scripted process id to an arbitrary
number (42) since the current value (0) is considered invalid.

Differential Revision: https://reviews.llvm.org/D148153

Signed-off-by: Med Ismail Bennani <[email protected]>
(cherry picked from commit 9cbdfcd)

Author: medismailben

lldb/examples/python/scripted_process/crashlog_scripted_process.py

@@ -101,9 +101,6 @@ def get_loaded_images(self):
         # from it.
         return self.loaded_images
 
-    def get_process_id(self) -> int:
-        return self.pid
-
     def should_stop(self) -> bool:
         return True
 

lldb/examples/python/scripted_process/scripted_process.py

@@ -47,6 +47,7 @@ def __init__(self, exe_ctx, args):
         self.loaded_images = []
         self.metadata = {}
         self.capabilities = {}
+        self.pid = 42
 
     def get_capabilities(self):
         """ Get a dictionary containing the process capabilities.
@@ -138,7 +139,7 @@ def get_process_id(self):
         Returns:
             int: The scripted process identifier.
         """
-        return 0
+        return self.pid
 
     def launch(self):
         """ Simulate the scripted process launch.

lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp

@@ -161,7 +161,10 @@ Status ScriptedProcess::DoLaunch(Module *exe_module,
   return error;
 }
 
+void ScriptedProcess::DidLaunch() { m_pid = GetInterface().GetProcessID(); }
+
 void ScriptedProcess::DidResume() {
+  // Update the PID again, in case the user provided a placeholder pid at launch
   m_pid = GetInterface().GetProcessID();
   GetLoadedDynamicLibrariesInfos();
 }

lldb/source/Plugins/Process/scripted/ScriptedProcess.h

@@ -47,6 +47,8 @@ class ScriptedProcess : public Process {
 
   Status DoLaunch(Module *exe_module, ProcessLaunchInfo &launch_info) override;
 
+  void DidLaunch() override;
+
   void DidResume() override;
 
   Status DoResume() override;