[Args] Handle backticks

[JDevlieghere]

Summary

Currently LLDB crashes when autocompleting a command that ends with a backtick.

 ./bin/lldb test.tmp.out
(lldb) target create "test.tmp.out"
Current executable set to 'test.tmp.out' (x86_64).
(lldb) b main
Breakpoint 1: where = TestGDBRemoteRepro.test.tmp.out`main + 22 at simple.c:16:5, address = 0x0000000100000f76
(lldb) r
Process 66563 launched: 'test.tmp.out' (x86_64)
Process 66563 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000100000f76 TestGDBRemoteRepro.test.tmp.out`main(argc=1, argv=0x00007ffeefbff608) at simple.c:16:5
   13   }
   14
   15   int main (int argc, char const *argv[]) {
-> 16       foo();
   17       return 0;
   18   }
(lldb) bt`Assertion failed: (false && "Unhandled quote character"), function EscapeLLDBCommandArgument, file /Users/jonas/llvm/git-mono/llvm-project/llvm/tools/lldb/source/Utility/Args.cpp, line 650.

[labath]

Given the current way lldb command interpreter parser does things (which tries to model a posix shell), (one of) the correct ways to do '-quoting would be to replace each ' char by '\''.

However, this isn't the only problem with how we do tab-completion of quoted strings, so if you want to just fix the crash, I think this is fine.

[JDevlieghere]

In D59779#1441705, @labath wrote:

Given the current way lldb command interpreter parser does things (which tries to model a posix shell), (one of) the correct ways to do '-quoting would be to replace each ' char by '\''.

However, this isn't the only problem with how we do tab-completion of quoted strings, so if you want to just fix the crash, I think this is fine.

Yeah. I didn't dive into the intricacies of this function.

source/Utility/Args.cpp

 
 std::string Args::EscapeLLDBCommandArgument(const std::string &arg,
                                             char quote_char) {
   const char *chars_to_escape = nullptr;
   switch (quote_char) {
   case '\0':
     chars_to_escape = " \t\\'\"`";
     break;
-  case '\'':
-    chars_to_escape = "";
-    break;
   case '"':
     chars_to_escape = "$\"`\\";
     break;
+  case '`':
+  case '\'':
+    return arg;
   default:
     assert(false && "Unhandled quote character");
+    return arg;
   }
 
   std::string res;
   res.reserve(arg.size());
   for (char c : arg) {
     if (::strchr(chars_to_escape, c))
       res.push_back('\\');
     res.push_back(c);

unittests/Utility/ArgsTest.cpp

 
 TEST(ArgsTest, GetArgumentArrayRef) {
   Args args("foo bar");
   auto ref = args.GetArgumentArrayRef();
   ASSERT_EQ(2u, ref.size());
   EXPECT_STREQ("foo", ref[0]);
   EXPECT_STREQ("bar", ref[1]);
 }
+
+TEST(ArgsTest, EscapeLLDBCommandArgument) {
+  const std::string foo = "foo'";
+  EXPECT_EQ("foo\\'", Args::EscapeLLDBCommandArgument(foo, '\0'));
+  EXPECT_EQ("foo'", Args::EscapeLLDBCommandArgument(foo, '\''));
+  EXPECT_EQ("foo'", Args::EscapeLLDBCommandArgument(foo, '`'));
+  EXPECT_EQ("foo'", Args::EscapeLLDBCommandArgument(foo, '"'));
+
+  const std::string bar = "bar\"";
+  EXPECT_EQ("bar\\\"", Args::EscapeLLDBCommandArgument(bar, '\0'));
+  EXPECT_EQ("bar\"", Args::EscapeLLDBCommandArgument(bar, '\''));
+  EXPECT_EQ("bar\"", Args::EscapeLLDBCommandArgument(bar, '`'));
+  EXPECT_EQ("bar\\\"", Args::EscapeLLDBCommandArgument(bar, '"'));
+
+  const std::string baz = "baz`";
+  EXPECT_EQ("baz\\`", Args::EscapeLLDBCommandArgument(baz, '\0'));
+  EXPECT_EQ("baz`", Args::EscapeLLDBCommandArgument(baz, '\''));
+  EXPECT_EQ("baz`", Args::EscapeLLDBCommandArgument(baz, '`'));
+  EXPECT_EQ("baz\\`", Args::EscapeLLDBCommandArgument(baz, '"'));
+
+  const std::string quux = "quux\t";
+  EXPECT_EQ("quux\\\t", Args::EscapeLLDBCommandArgument(quux, '\0'));
+  EXPECT_EQ("quux\t", Args::EscapeLLDBCommandArgument(quux, '\''));
+  EXPECT_EQ("quux\t", Args::EscapeLLDBCommandArgument(quux, '`'));
+  EXPECT_EQ("quux\t", Args::EscapeLLDBCommandArgument(quux, '"'));
+}