Fix treating undefined preprocessor identifiers as error.

src/OpenGL/compiler/preprocessor/Diagnostics.cpp

@@ -109,6 +109,8 @@ std::string Diagnostics::message(ID id)
           return "invalid file number";
       case INVALID_LINE_DIRECTIVE:
           return "invalid line directive";
+      case UNDEFINED_IDENTIFIER:
+          return "undefined identifier";
       // Errors end.
       // Warnings begin.
       case EOF_IN_DIRECTIVE:

src/OpenGL/compiler/preprocessor/Diagnostics.h

@@ -61,6 +61,7 @@ class Diagnostics
         INVALID_LINE_NUMBER,
         INVALID_FILE_NUMBER,
         INVALID_LINE_DIRECTIVE,
+		UNDEFINED_IDENTIFIER,
         ERROR_END,
 
         WARNING_BEGIN,

src/OpenGL/compiler/preprocessor/ExpressionParser.cpp

@@ -1762,6 +1762,16 @@ int yylex(YYSTYPE* lvalp, Context* context)
         type = TOK_CONST_INT;
         break;
       }
+      case pp::Token::IDENTIFIER:
+        // Defined identifiers should have been expanded already.
+        // Unlike the C/C++ preprocessor, it does not default to 0.
+        // Use of such identifiers causes an error.
+        context->diagnostics->report(pp::Diagnostics::UNDEFINED_IDENTIFIER,
+                                     token->location, token->text);
+
+        *lvalp = 0;
+        type = TOK_CONST_INT;
+        break;
       case pp::Token::OP_OR: type = TOK_OP_OR; break;
       case pp::Token::OP_AND: type = TOK_OP_AND; break;
       case pp::Token::OP_NE: type = TOK_OP_NE; break;

src/OpenGL/compiler/preprocessor/ExpressionParser.y

@@ -194,6 +194,16 @@ int yylex(YYSTYPE* lvalp, Context* context)
         type = TOK_CONST_INT;
         break;
       }
+      case pp::Token::IDENTIFIER:
+        // Defined identifiers should have been expanded already.
+        // Unlike the C/C++ preprocessor, it does not default to 0.
+        // Use of such identifiers causes an error.
+        context->diagnostics->report(pp::Diagnostics::UNDEFINED_IDENTIFIER,
+                                     token->location, token->text);
+
+        *lvalp = 0;
+        type = TOK_CONST_INT;
+        break;
       case pp::Token::OP_OR: type = TOK_OP_OR; break;
       case pp::Token::OP_AND: type = TOK_OP_AND; break;
       case pp::Token::OP_NE: type = TOK_OP_NE; break;