[lld][WebAssembly] Fix use after free of archive path

[sbc100]

Summary

This was fixed in the ELF backend in https://reviews.llvm.org/D34554.

[dschuff]

lld/wasm/Driver.cpp

232

Should these debug prints be behind LLVM_DEBUG?

[sbc100]

• revert

lld/wasm/Driver.cpp

void LinkerDriver::addFile(StringRef path) {
   MemoryBufferRef mbref = *buffer;
 
   switch (identify_magic(mbref.getBuffer())) {
   case file_magic::archive: {
     SmallString<128> importFile = path;
     path::replace_extension(importFile, ".imports");
     if (fs::exists(importFile))
       readImportFile(importFile.str());
+    dbgs() << "new archive: " << mbref.getBufferIdentifier() << "\n";
 
     // Handle -whole-archive.
     if (inWholeArchive) {
       for (MemoryBufferRef &m : getArchiveMembers(mbref))
         files.push_back(createObjectFile(m, path));
       return;
     }
 
     std::unique_ptr<Archive> file =
         CHECK(Archive::create(mbref), path + ": failed to parse archive");
 
     if (!file->isEmpty() && !file->hasSymbolTable()) {
       error(mbref.getBufferIdentifier() +
             ": archive has no index; run ranlib to add one");
     }
 
-    files.push_back(make<ArchiveFile>(mbref));
+    auto* F = make<ArchiveFile>(mbref);
+    dbgs() << "new archive: " << F->getName() << "\n";
+    files.push_back(F);
     return;
   }
   case file_magic::bitcode:
   case file_magic::wasm_object:
     files.push_back(createObjectFile(mbref));
     break;
   default:
     error("unknown file type: " + mbref.getBufferIdentifier());
   }
 }
 
 // Add a given library by searching it from input search paths.
 void LinkerDriver::addLibrary(StringRef name) {
+  dbgs()  << "XXX\n";
   for (StringRef dir : config->searchPaths) {
     if (Optional<std::string> s = findFile(dir, "lib" + name + ".a")) {
       addFile(*s);
       return;
     }
   }
 
   error("unable to find library -l" + name);

lld/wasm/InputFiles.h

public:
   virtual ~InputFile() {}
 
   // Returns the filename.
   StringRef getName() const { return mb.getBufferIdentifier(); }
 
   Kind kind() const { return fileKind; }
 
   // An archive file name if this file is created from an archive.
-  StringRef archiveName;
+  std::string archiveName;
 
   ArrayRef<Symbol *> getSymbols() const { return symbols; }
 
   MutableArrayRef<Symbol *> getMutableSymbols() { return symbols; }
 
 protected:
   InputFile(Kind k, MemoryBufferRef m) : mb(m), fileKind(k) {}
   MemoryBufferRef mb;