[clang-offload-bundler] use std::forward_list for storing temp file names [NFC]

[sdmitriev]

Summary

Use a different container that preserves existing elements on modification
for storing temporary file names. Current container can make StringRefs
returned earlier invalid on reallocation.

[ABataev]

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

411

What about llvm::iplist?

[sdmitriev]

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

411

It can be changed to iplist as well, but why do you think it is a better option here?

[ABataev]

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

411

Just better to use LLVM API if possible.

[sdmitriev]

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

411

Well, I do not think it will bring any benefits here compared to the forward_list. iplist is an intrusive list, so it requires an element to provide access to prev/next elements in the list, and because of that element type should be derived from ilist_node. So, switching to iplist would require adding one more class for the list element type. I agree that it is not difficult to do, but I just do not see why it needs to be done.

[ABataev]

LG

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

 #include "llvm/Support/Signals.h"
 #include "llvm/Support/StringSaver.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
+#include <forward_list>
 #include <memory>
 #include <string>
 #include <system_error>
 #include <utility>
 
 using namespace llvm;
 using namespace llvm::object;
 
public:
   }
 
   // Creates temporary file with given contents.
   Expected<StringRef> Create(Optional<ArrayRef<char>> Contents) {
     SmallString<128u> File;
     if (std::error_code EC =
             sys::fs::createTemporaryFile("clang-offload-bundler", "tmp", File))
       return createFileError(File, EC);
-    Files.push_back(File);
+    Files.push_front(File);
 
     if (Contents) {
       std::error_code EC;
       raw_fd_ostream OS(File, EC);
       if (EC)
         return createFileError(File, EC);
       OS.write(Contents->data(), Contents->size());
     }
-    return Files.back();
+    return Files.front();
   }
 
 private:
-  SmallVector<SmallString<128u>, 4u> Files;
+  std::forward_list<SmallString<128u>> Files;
 };
 
 } // end anonymous namespace
 
 /// Handler for object files. The bundles are organized by sections with a
 /// designated name.
 ///
 /// To unbundle, we just copy the contents of the designated section.