[lldb] Respect empty arguments in target.run-args

[bulbazord]

Summary

Currently empty arguments are not respected. They are silently dropped
in two places: (1) when extracting them from the target.run-args
setting and (2) when constructing the lldb-argdumper invocation.

(1) is actually a regression from a few years ago. We did not always
drop empty arguments. See 31d97a5c8ab78c619deada0cdb1fcf64021d25dd.

rdar://106279228

[DavidSpickett]

A bit surprised there wasn't an existing test to just add an extra argument to, but looks good to me.

[labath]

lldb/source/Host/common/ProcessLaunchInfo.cpp

324–325

Shouldn't this belong inside Args::GetShellSafeArgument? I don't think there's any situation where the current behavior of the function would be correct (and this is the only caller of the function anyway...)

[bulbazord]

lldb/source/Host/common/ProcessLaunchInfo.cpp

324–325

As in, we should set safe_arg to \"\" when argv[I] is the empty string (e.g. safe_arg should never be empty)? If that's what you're suggesting, I think that would be a reasonable thing to do.

[labath]

lldb/source/Host/common/ProcessLaunchInfo.cpp

324–325

I think it is. What I'm saying is that Args::GetShellSafeArgument(???, "") should automatically return "\"\" instead of needing to fix this up afterwards...

lldb/source/Host/common/ProcessLaunchInfo.cpp

if (m_shell) {
         // to be used as is
         if (argv[0] && !argv[1])
           shell_command.Printf("%s", argv[0]);
         else
           return false;
       } else {
         for (size_t i = 0; argv[i] != nullptr; ++i) {
           std::string safe_arg = Args::GetShellSafeArgument(m_shell, argv[i]);
+          if (safe_arg.empty())
+            safe_arg = "\"\"";
           // Add a space to separate this arg from the previous one.
           shell_command.PutCString(" ");
           shell_command.PutCString(safe_arg);
         }
       }
       shell_arguments.AppendArgument(shell_command.GetString());
       m_executable = m_shell;
       m_arguments = shell_arguments;

lldb/source/Interpreter/OptionValueArgs.cpp

 
 using namespace lldb;
 using namespace lldb_private;
 
 size_t OptionValueArgs::GetArgs(Args &args) const {
   args.Clear();
   for (const auto &value : m_values) {
     llvm::StringRef string_value = value->GetStringValue();
-    if (!string_value.empty())
-      args.AppendArgument(string_value);
   }
 
   return args.GetArgumentCount();
 }

lldb/test/Shell/Driver/Inputs/dumpargs.c

+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+  for (int i = 0; i < argc; i++) {
+    printf("argv[%d] = \"%s\"\n", i, argv[i]);
+  }
+  return 0;
+}

lldb/test/Shell/Driver/TestEmptyArgument.test

+# RUN: %clang_host %S/Inputs/dumpargs.c -o %t.out
+# RUN: %lldb -b -o "r" %t.out -- "one" "two" "" "three" | FileCheck %s
+
+# CHECK: argv[1] = "one"
+# CHECK: argv[2] = "two"
+# CHECK: argv[3] = ""
+# CHECK: argv[4] = "three"