Fix two bugs in TGParser::ParseValue

[Paul-C-Anagnostopoulos]

Summary

TGParser::ParseValue contains two recursive calls, one to parse the RHS of a list paste operator and one to parse the RHS of a paste operator in a class/def name. Both of these calls neglect to check the return value to see if it is null (because of some error). This causes a crash in the next line of code, which uses the return value. The code now checks for null returns.

[Paul-C-Anagnostopoulos]

Do I need to reformat the code as Lint suggests? Most of the if (!xxx) return ... tests in the code are on one line.

[nhaehnle]

Do I need to reformat the code as Lint suggests? Most of the if (!xxx) return ... tests in the code are on one line.

Yes, please do. Those single-line checks are increasingly rare in the LLVM code base for IMHO good reasons, let's not add new ones even if this code happens to be fairly old and not follow newer customs.

The change LGTM apart from that, thanks!

[Paul-C-Anagnostopoulos]

Reformatted the two lines of code correctly.

@nhaehnle, could you do me the favor of committing this?

[nhaehnle]

Hmm, forgot to adjust the author field to you for that commit. Sorry about that, I'm doing it for the other ones.

llvm/lib/TableGen/TGParser.cpp

case tgtok::paste:
         switch (Lex.getCode()) {
         case tgtok::colon:
         case tgtok::semi:
         case tgtok::l_brace:
           Result = LHS; // trailing paste, ignore.
           break;
         default:
           Init *RHSResult = ParseValue(CurRec, ItemType, ParseNameMode);
+          if (!RHSResult)
+            return nullptr;
           Result = BinOpInit::getListConcat(LHS, RHSResult);
         }
         break;
       }
 
       // Create a !strconcat() operation, first casting each operand to
       // a string if necessary.
       if (LHS->getType() != StringRecTy::get()) {
case tgtok::paste:
         // because they are unlikely to be useful.
 
         // Trailing paste, concat with an empty string.
         RHS = StringInit::get("");
         break;
 
       default:
         Init *RHSResult = ParseValue(CurRec, nullptr, ParseNameMode);
+        if (!RHSResult)
+          return nullptr;
         RHS = dyn_cast<TypedInit>(RHSResult);
         if (!RHS) {
           Error(PasteLoc, "RHS of paste is not typed!");
           return nullptr;
         }
 
         if (RHS->getType() != StringRecTy::get()) {
           auto CastRHS = dyn_cast<TypedInit>(

llvm/test/TableGen/paste-reserved.td

+// RUN: not llvm-tblgen -DERROR1 %s 2>&1 | FileCheck --check-prefix=ERROR1 %s
+// RUN: not llvm-tblgen -DERROR2 %s 2>&1 | FileCheck --check-prefix=ERROR2 %s
+
+defvar list1 = ["foo", "bar", "snork"];
+
+// Pasting a list with a reserved word should produce an error.
+
+#ifdef ERROR1
+def list_paste {
+  list<string> the_list = list1 # in;
+}
+// ERROR1: error: Unknown token when parsing a value
+#endif
+
+
+// Pasting an identifier with a reserved word should produce an error.
+
+#ifdef ERROR2
+def name_paste#in {
+}
+// ERROR2: error: Unknown token when parsing a value
+#endif