Hide stderr output from lldb-argdumper

[aprantl]

Summary

Under very specific circumstances the default shell /bin/sh might print stuff to stderr before launching lldb-argdumper, which then confuses the JSON parser. This patch suppresses stderr output from lldb-argdumper to avoid this situation.

rdar://problem/50149390

[clayborg]

lgtm

lldb/include/lldb/Host/Host.h

public:
 
   /// Perform expansion of the command-line for this launch info This can
   /// potentially involve wildcard expansion
   /// environment variable replacement, and whatever other
   /// argument magic the platform defines as part of its typical
   /// user experience
   static Status ShellExpandArguments(ProcessLaunchInfo &launch_info);
 
-  // TODO: Convert this function to take a StringRef.
-  static Status RunShellCommand(
-      const char *command,         // Shouldn't be NULL
-      const FileSpec &working_dir, // Pass empty FileSpec to use the current
-                                   // working directory
-      int *status_ptr, // Pass NULL if you don't want the process exit status
-      int *signo_ptr,  // Pass NULL if you don't want the signal that caused the
-                       // process to exit
-      std::string
-          *command_output, // Pass NULL if you don't want the command output
-      const Timeout<std::micro> &timeout, bool run_in_default_shell = true);
-
-  static Status RunShellCommand(
-      const Args &args,
-      const FileSpec &working_dir, // Pass empty FileSpec to use the current
-                                   // working directory
-      int *status_ptr, // Pass NULL if you don't want the process exit status
-      int *signo_ptr,  // Pass NULL if you don't want the signal that caused the
-                       // process to exit
-      std::string
-          *command_output, // Pass NULL if you don't want the command output
-      const Timeout<std::micro> &timeout, bool run_in_default_shell = true);
+  /// Run a shell command.
+  /// \arg command  shouldn't be NULL
+  /// \arg working_dir Pass empty FileSpec to use the current working directory
+  /// \arg status_ptr  Pass NULL if you don't want the process exit status
+  /// \arg signo_ptr   Pass NULL if you don't want the signal that caused the
+  ///                  process to exit
+  /// \arg command_output  Pass NULL if you don't want the command output
+  /// \arg hide_stderr if this is false, redirect stderr to stdout
+  /// TODO: Convert this function to take a StringRef.
+  static Status RunShellCommand(const char *command,
+                                const FileSpec &working_dir, int *status_ptr,
+                                int *signo_ptr, std::string *command_output,
+                                const Timeout<std::micro> &timeout,
+                                bool run_in_default_shell = true,
+                                bool hide_stderr = false);
+
+  /// Run a shell command.
+  /// \arg working_dir Pass empty FileSpec to use the current working directory
+  /// \arg status_ptr  Pass NULL if you don't want the process exit status
+  /// \arg signo_ptr   Pass NULL if you don't want the signal that caused the
+  ///                  process to exit
+  /// \arg command_output  Pass NULL if you don't want the command output
+  /// \arg hide_stderr if this is false, redirect stderr to stdout
+  static Status RunShellCommand(const Args &args, const FileSpec &working_dir,
+                                int *status_ptr, int *signo_ptr,
+                                std::string *command_output,
+                                const Timeout<std::micro> &timeout,
+                                bool run_in_default_shell = true,
+                                bool hide_stderr = false);
 
   static bool OpenFileInExternalEditor(const FileSpec &file_spec,
                                        uint32_t line_no);
 
   static Environment GetEnvironment();
 
   static std::unique_ptr<Connection>
   CreateDefaultConnection(llvm::StringRef url);

lldb/source/Host/common/Host.cpp

MonitorShellCommand(std::shared_ptr<ShellInfo> shell_info, lldb::pid_t pid,
   shell_info->process_reaped.SetValue(true, eBroadcastAlways);
   return true;
 }
 
 Status Host::RunShellCommand(const char *command, const FileSpec &working_dir,
                              int *status_ptr, int *signo_ptr,
                              std::string *command_output_ptr,
                              const Timeout<std::micro> &timeout,
-                             bool run_in_default_shell) {
+                             bool run_in_default_shell,
+                             bool hide_stderr) {
   return RunShellCommand(Args(command), working_dir, status_ptr, signo_ptr,
-                         command_output_ptr, timeout, run_in_default_shell);
+                         command_output_ptr, timeout, run_in_default_shell,
+                         hide_stderr);
 }
 
 Status Host::RunShellCommand(const Args &args, const FileSpec &working_dir,
                              int *status_ptr, int *signo_ptr,
                              std::string *command_output_ptr,
                              const Timeout<std::micro> &timeout,
-                             bool run_in_default_shell) {
+                             bool run_in_default_shell,
+                             bool hide_stderr) {
   Status error;
   ProcessLaunchInfo launch_info;
   launch_info.SetArchitecture(HostInfo::GetArchitecture());
   if (run_in_default_shell) {
     // Run the command in a shell
     launch_info.SetShell(HostInfo::GetDefaultShell());
     launch_info.GetArguments().AppendArguments(args);
     const bool localhost = true;
if (FileSpec tmpdir_file_spec = HostInfo::GetProcessTempDir()) {
                                       output_file_path);
     } else {
       llvm::sys::fs::createTemporaryFile("lldb-shell-output.%%%%%%", "",
                                          output_file_path);
     }
   }
 
   FileSpec output_file_spec(output_file_path.c_str());
-
+  // Set up file descriptors.
   launch_info.AppendSuppressFileAction(STDIN_FILENO, true, false);
-  if (output_file_spec) {
+  if (output_file_spec)
     launch_info.AppendOpenFileAction(STDOUT_FILENO, output_file_spec, false,
                                      true);
-    launch_info.AppendDuplicateFileAction(STDOUT_FILENO, STDERR_FILENO);
-  } else {
+  else
     launch_info.AppendSuppressFileAction(STDOUT_FILENO, false, true);
+
+  if (output_file_spec && !hide_stderr)
+    launch_info.AppendDuplicateFileAction(STDOUT_FILENO, STDERR_FILENO);
+  else
     launch_info.AppendSuppressFileAction(STDERR_FILENO, false, true);
-  }
 
   std::shared_ptr<ShellInfo> shell_info_sp(new ShellInfo());
   const bool monitor_signals = false;
   launch_info.SetMonitorProcessCallback(
       std::bind(MonitorShellCommand, shell_info_sp, std::placeholders::_1,
                 std::placeholders::_2, std::placeholders::_3,
                 std::placeholders::_4),
       monitor_signals);

lldb/source/Host/macosx/objcxx/Host.mm

if (!FileSystem::Instance().Exists(cwd)) {
             "cwd does not exist; cannot launch with shell argument expansion");
         return error;
       } else {
         FileSpec working_dir(wd);
         free(wd);
         launch_info.SetWorkingDirectory(working_dir);
       }
     }
+    bool run_in_default_shell = true;
+    bool hide_stderr = true;
     RunShellCommand(expand_command, cwd, &status, nullptr, &output,
-                    std::chrono::seconds(10));
+                    std::chrono::seconds(10), run_in_default_shell,
+                    hide_stderr);
 
     if (status != 0) {
       error.SetErrorStringWithFormat("lldb-argdumper exited with error %d",
                                      status);
       return error;
     }
 
     auto data_sp = StructuredData::ParseJSON(output);