From: Chris Lattner <sabre@nondot.org>
Date: Fri, 17 Apr 2009 23:30:53 +0000 (+0000)
Subject: #line is allowed to have macros that expand to nothing after them.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ab82f41b217ce588a9456c0b4411f219d3ed0df8;p=clang

#line is allowed to have macros that expand to nothing after them.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@69401 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/clang/Lex/Preprocessor.h b/include/clang/Lex/Preprocessor.h
index 9e4278515b..2184acf0e3 100644
--- a/include/clang/Lex/Preprocessor.h
+++ b/include/clang/Lex/Preprocessor.h
@@ -580,8 +580,9 @@ public:
   void HandleDirective(Token &Result);
 
   /// CheckEndOfDirective - Ensure that the next token is a tok::eom token.  If
-  /// not, emit a diagnostic and consume up until the eom.
-  void CheckEndOfDirective(const char *Directive);
+  /// not, emit a diagnostic and consume up until the eom.  If EnableMacros is
+  /// true, then we consider macros that expand to zero tokens as being ok.
+  void CheckEndOfDirective(const char *Directive, bool EnableMacros = false);
   
   /// DiscardUntilEndOfDirective - Read and discard all tokens remaining on the
   /// current line until the tok::eom token is found.
diff --git a/lib/Lex/PPDirectives.cpp b/lib/Lex/PPDirectives.cpp
index 742076956d..ce86d0edca 100644
--- a/lib/Lex/PPDirectives.cpp
+++ b/lib/Lex/PPDirectives.cpp
@@ -101,12 +101,17 @@ void Preprocessor::ReadMacroName(Token &MacroNameTok, char isDefineUndef) {
 }
 
 /// CheckEndOfDirective - Ensure that the next token is a tok::eom token.  If
-/// not, emit a diagnostic and consume up until the eom.
-void Preprocessor::CheckEndOfDirective(const char *DirType) {
+/// not, emit a diagnostic and consume up until the eom.  If EnableMacros is
+/// true, then we consider macros that expand to zero tokens as being ok.
+void Preprocessor::CheckEndOfDirective(const char *DirType, bool EnableMacros) {
   Token Tmp;
-  // Lex unexpanded tokens: macros might expand to zero tokens, causing us to
-  // miss diagnosing invalid lines.
-  LexUnexpandedToken(Tmp);
+  // Lex unexpanded tokens for most directives: macros might expand to zero
+  // tokens, causing us to miss diagnosing invalid lines.  Some directives (like
+  // #line) allow empty macros.
+  if (EnableMacros)
+    Lex(Tmp);
+  else
+    LexUnexpandedToken(Tmp);
   
   // There should be no tokens after the directive, but we allow them as an
   // extension.
@@ -694,8 +699,9 @@ void Preprocessor::HandleLineDirective(Token &Tok) {
     FilenameID = SourceMgr.getLineTableFilenameID(Literal.GetString(),
                                                   Literal.GetStringLength());
     
-    // Verify that there is nothing after the string, other than EOM.
-    CheckEndOfDirective("line");
+    // Verify that there is nothing after the string, other than EOM.  Because
+    // of C99 6.10.4p5, macros that expand to empty tokens are ok.
+    CheckEndOfDirective("line", true);
   }
   
   SourceMgr.AddLineNote(DigitTok.getLocation(), LineNo, FilenameID);
diff --git a/test/Preprocessor/line-directive.c b/test/Preprocessor/line-directive.c
index 66efae94d5..1dd8b292d2 100644
--- a/test/Preprocessor/line-directive.c
+++ b/test/Preprocessor/line-directive.c
@@ -60,3 +60,11 @@ typedef int z1;  // ok
 
 typedef int w;  // expected-note {{previous definition is here}}
 typedef int w;  // expected-error {{redefinition of typedef 'w' is invalid in C}}
+
+
+// This should not produce an "extra tokens at end of #line directive" warning,
+// because #line is allowed to contain expanded tokens.
+#define EMPTY()
+#line 2 "foo.c" EMPTY( )
+#line 2 "foo.c" NONEMPTY( )  // expected-warning{{extra tokens at end of #line directive}}
+