[coff] use newlines instead of spaces as separators in msvclto response file

[inglorion]

Summary

Fixes PR32689: /msvclto creates response files with lines
that are too long for msvc's linker (LNK1170).

[davide]

I'm surprised we don't have a test for this? (I assume it needs link.exe but that should be available on some bots)

[inglorion]

@davide, we could extract the response file generation into its own function and write a unit test for it. On the other hand, I don't want to spend too much time polishing msvclto - I'd rather spend time on making it unnecessary.

[davide]

In D32185#729603, @inglorion wrote:

@davide, we could extract the response file generation into its own function and write a unit test for it. On the other hand, I don't want to spend too much time polishing msvclto - I'd rather spend time on making it unnecessary.

If it will go away soon, fair enough.

[hans]

lgtm

COFF/Driver.cpp

std::pair<StringRef, std::error_code> Ret =
                          /*Thin=*/false);
   if (Ret.second)
     error("failed to create a new archive " + S.str() + ": " + Ret.first);
   return Temp;
 }
 
 // Create response file contents and invoke the MSVC linker.
 void LinkerDriver::invokeMSVC(opt::InputArgList &Args) {
-  std::string Rsp = "/nologo ";
+  std::string Rsp = "/nologo\n";
   std::vector<std::string> Temps;
 
   for (auto *Arg : Args) {
     switch (Arg->getOption().getID()) {
     case OPT_linkrepro:
     case OPT_lldmap:
     case OPT_lldmap_file:
     case OPT_lldsavetemps:
     case OPT_msvclto:
       // LLD-specific options are stripped.
       break;
     case OPT_opt:
       if (!StringRef(Arg->getValue()).startswith("lld"))
         Rsp += toString(Arg) + " ";
       break;
     case OPT_INPUT: {
       if (Optional<StringRef> Path = doFindFile(Arg->getValue())) {
         if (Optional<std::string> S = filterBitcodeFiles(*Path, Temps))
-          Rsp += quote(*S) + " ";
+          Rsp += quote(*S) + "\n";
         continue;
       }
-      Rsp += quote(Arg->getValue()) + " ";
+      Rsp += quote(Arg->getValue()) + "\n";
       break;
     }
     default:
-      Rsp += toString(Arg) + " ";
+      Rsp += toString(Arg) + "\n";
     }
   }
 
   std::vector<StringRef> ObjectFiles = Symtab.compileBitcodeFiles();
   runMSVCLinker(Rsp, ObjectFiles);
 
   for (StringRef Path : Temps)
     sys::fs::remove(Path);

COFF/DriverUtils.cpp

 // Run MSVC link.exe for given in-memory object files.
 // Command line options are copied from those given to LLD.
 // This is for the /msvclto option.
 void runMSVCLinker(std::string Rsp, ArrayRef<StringRef> Objects) {
   // Write the in-memory object files to disk.
   std::vector<TemporaryFile> Temps;
   for (StringRef S : Objects) {
     Temps.emplace_back("lto", "obj", S);
-    Rsp += quote(Temps.back().Path) + " ";
+    Rsp += quote(Temps.back().Path) + "\n";
   }
 
   log("link.exe " + Rsp);
 
   // Run MSVC link.exe.
   Temps.emplace_back("lto", "rsp", Rsp);
   Executor E("link.exe");
   E.add(Twine("@" + Temps.back().Path));