[Support] Windows - Refactor argument serialization logic when executing process in Program.inc [NFC]

[rafaelauler]

Summary

This patch refactors the argument serialization logic used in the Execute function, used to launch new Windows processes. There is a critical step that joins char** arguments into a single string, building the command line used to launch the new process, and the readability of this code is improved if this part is refactored in its own helper function.

[• rafael]

LGTM with a check.

lib/Support/Windows/Program.inc

207

Don't you need a std::move in here?

[rafaelauler]

Thanks for reviewing it, could you please commit this? I don't have commit access. Or do you want me to change the helper function and make it return a raw pointer instead of a unique_ptr?

Cheers,
Rafael

[• rafael]

r216411.

lib/Support/Windows/Program.inc

if (Quoted) {
     len += PrecedingEscapes + 1;
   }
 
   return len;
 }
 
 }
 
-static bool Execute(ProcessInfo &PI, StringRef Program, const char **args,
-                    const char **envp, const StringRef **redirects,
-                    unsigned memoryLimit, std::string *ErrMsg) {
-  if (!sys::fs::can_execute(Program)) {
-    if (ErrMsg)
-      *ErrMsg = "program not executable";
-    return false;
-  }
-
-  // Windows wants a command line, not an array of args, to pass to the new
-  // process.  We have to concatenate them all, while quoting the args that
-  // have embedded spaces (or are empty).
-
+static std::unique_ptr<char[]> flattenArgs(const char **args) {
   // First, determine the length of the command line.
   unsigned len = 0;
   for (unsigned i = 0; args[i]; i++) {
     len += ArgLenWithQuotes(args[i]) + 1;
   }
 
   // Now build the command line.
   std::unique_ptr<char[]> command(new char[len+1]);
if (needsQuoting) {
       // Make sure our quote doesn't get escaped by a trailing backslash.
       p = EscapePrecedingEscapes(p, start, arg);
       *p++ = '"';
     }
     *p++ = ' ';
   }
 
   *p = 0;
+  return command;
+}
+
+static bool Execute(ProcessInfo &PI, StringRef Program, const char **args,
+                    const char **envp, const StringRef **redirects,
+                    unsigned memoryLimit, std::string *ErrMsg) {
+  if (!sys::fs::can_execute(Program)) {
+    if (ErrMsg)
+      *ErrMsg = "program not executable";
+    return false;
+  }
+
+  // Windows wants a command line, not an array of args, to pass to the new
+  // process.  We have to concatenate them all, while quoting the args that
+  // have embedded spaces (or are empty).
+  std::unique_ptr<char[]> command = flattenArgs(args);
 
   // The pointer to the environment block for the new process.
   std::vector<wchar_t> EnvBlock;
 
   if (envp) {
     // An environment block consists of a null-terminated block of
     // null-terminated strings. Convert the array of environment variables to
     // an environment block by concatenating them.