Reapply [Support] Fix recursive response file expansion guard

The test in the dependent revision has been fixed for Windows.

Original commit message:

Response file expansion limits the amount of expansion to prevent
potential infinite recursion. However, the current logic assumes that
any argument beginning with @ is a response file, which is not true for
e.g. `-Xlinker -rpath -Xlinker @executable_path/../lib` on Darwin.
Having too many of these non-response file arguments beginning with @
prevents actual response files from being expanded. Instead, limit based
on the number of successful response file expansions, which should still
prevent infinite recursion but also avoid false positives.

Differential Revision: https://reviews.llvm.org/D60631

> llvm-svn: 358452

llvm-svn: 358466

llvm/lib/Support/CommandLine.cpp

@@ -1040,7 +1040,7 @@ static bool ExpandResponseFile(StringRef FName, StringSaver &Saver,
 bool cl::ExpandResponseFiles(StringSaver &Saver, TokenizerCallback Tokenizer,
                              SmallVectorImpl<const char *> &Argv,
                              bool MarkEOLs, bool RelativeNames) {
-  unsigned RspFiles = 0;
+  unsigned ExpandedRspFiles = 0;
   bool AllExpanded = true;
 
   // Don't cache Argv.size() because it can change.
@@ -1058,14 +1058,16 @@ bool cl::ExpandResponseFiles(StringSaver &Saver, TokenizerCallback Tokenizer,
 
     // If we have too many response files, leave some unexpanded.  This avoids
     // crashing on self-referential response files.
-    if (RspFiles++ > 20)
+    if (ExpandedRspFiles > 20)
       return false;
 
     // Replace this response file argument with the tokenization of its
     // contents.  Nested response files are expanded in subsequent iterations.
     SmallVector<const char *, 0> ExpandedArgv;
-    if (!ExpandResponseFile(Arg + 1, Saver, Tokenizer, ExpandedArgv,
-                            MarkEOLs, RelativeNames)) {
+    if (ExpandResponseFile(Arg + 1, Saver, Tokenizer, ExpandedArgv, MarkEOLs,
+                           RelativeNames)) {
+      ++ExpandedRspFiles;
+    } else {
       // We couldn't read this file, so we leave it in the argument stream and
       // move on.
       AllExpanded = false;

llvm/unittests/Support/CommandLineTest.cpp

@@ -816,6 +816,43 @@ TEST(CommandLineTest, RecursiveResponseFiles) {
     EXPECT_STREQ(Argv[i], ResponseFileRef.c_str());
 }
 
+TEST(CommandLineTest, ResponseFilesAtArguments) {
+  SmallString<128> TestDir;
+  std::error_code EC = sys::fs::createUniqueDirectory("unittest", TestDir);
+  EXPECT_TRUE(!EC);
+
+  SmallString<128> ResponseFilePath;
+  sys::path::append(ResponseFilePath, TestDir, "test.rsp");
+
+  std::ofstream ResponseFile(ResponseFilePath.c_str());
+  EXPECT_TRUE(ResponseFile.is_open());
+  ResponseFile << "-foo" << "\n";
+  ResponseFile << "-bar" << "\n";
+  ResponseFile.close();
+
+  // Ensure we expand rsp files after lots of non-rsp arguments starting with @.
+  constexpr size_t NON_RSP_AT_ARGS = 64;
+  SmallVector<const char *, 4> Argv = {"test/test"};
+  Argv.append(NON_RSP_AT_ARGS, "@non_rsp_at_arg");
+  std::string ResponseFileRef = std::string("@") + ResponseFilePath.c_str();
+  Argv.push_back(ResponseFileRef.c_str());
+
+  BumpPtrAllocator A;
+  StringSaver Saver(A);
+  bool Res = cl::ExpandResponseFiles(Saver, cl::TokenizeGNUCommandLine, Argv,
+                                     false, false);
+  EXPECT_FALSE(Res);
+
+  // ASSERT instead of EXPECT to prevent potential out-of-bounds access.
+  ASSERT_EQ(Argv.size(), 1 + NON_RSP_AT_ARGS + 2);
+  size_t i = 0;
+  EXPECT_STREQ(Argv[i++], "test/test");
+  for (; i < 1 + NON_RSP_AT_ARGS; ++i)
+    EXPECT_STREQ(Argv[i], "@non_rsp_at_arg");
+  EXPECT_STREQ(Argv[i++], "-foo");
+  EXPECT_STREQ(Argv[i++], "-bar");
+}
+
 TEST(CommandLineTest, SetDefautValue) {
   cl::ResetCommandLineParser();