Handle multiple escaped newlines between */ correctly

[lodewillems]

Summary

Clang currently only recognizes a single escaped line between the end characters
of a block comment.

Fixes bug 15706

[lodewillems]

Made obsolete by commit de6164ec4da0cfea1b0d0e472c432ea1be4d9c29

clang/lib/Lex/Lexer.cpp

 /// a diagnostic if so.  We know that the newline is inside of a block comment.
 static bool isEndOfBlockCommentWithEscapedNewLine(const char *CurPtr,
                                                   Lexer *L) {
   assert(CurPtr[0] == '\n' || CurPtr[0] == '\r');
 
   // Back up off the newline.
   --CurPtr;
 
+  bool HasSpace = false;
+  while (true) {
     // If this is a two-character newline sequence, skip the other character.
     if (CurPtr[0] == '\n' || CurPtr[0] == '\r') {
       // \n\n or \r\r -> not escaped newline.
       if (CurPtr[0] == CurPtr[1])
         return false;
       // \n\r or \r\n -> skip the newline.
       --CurPtr;
     }
 
     // If we have horizontal whitespace, skip over it.  We allow whitespace
     // between the slash and newline.
-  bool HasSpace = false;
     while (isHorizontalWhitespace(*CurPtr) || *CurPtr == 0) {
       --CurPtr;
       HasSpace = true;
     }
 
     // If we have a slash, we know this is an escaped newline.
     if (*CurPtr == '\\') {
-    if (CurPtr[-1] != '*') return false;
+      // Found the *, we're done
+      if (CurPtr[-1] == '*') break;
+
+      // Found another possible escaped newline
+      if (CurPtr[-1] == '\n' || CurPtr[-1] == '\r') {
+        --CurPtr;
+        continue;
+      }
+
+      return false;
     } else {
       // It isn't a slash, is it the ?? / trigraph?
-    if (CurPtr[0] != '/' || CurPtr[-1] != '?' || CurPtr[-2] != '?' ||
-        CurPtr[-3] != '*')
+      if (CurPtr[0] != '/' || CurPtr[-1] != '?' || CurPtr[-2] != '?')
         return false;
 
       // This is the trigraph ending the comment.  Emit a stern warning!
       CurPtr -= 2;
 
+      if (CurPtr[-1] == '*') {
         // If no trigraphs are enabled, warn that we ignored this trigraph and
         // ignore this * character.
         if (!L->getLangOpts().Trigraphs) {
           if (!L->isLexingRawMode())
             L->Diag(CurPtr, diag::trigraph_ignored_block_comment);
           return false;
         }
         if (!L->isLexingRawMode())
           L->Diag(CurPtr, diag::trigraph_ends_block_comment);
+
+        break;
+      } else if (CurPtr[-1] == '\n' || CurPtr[-1] == '\r') {
+        // If no trigraphs are enabled, warn that we ignored this trigraph
+        if (!L->getLangOpts().Trigraphs) {
+          if (!L->isLexingRawMode())
+            L->Diag(CurPtr, diag::trigraph_ignored);
+          return false;
+        }
+        --CurPtr;
+        continue;
+      }
+
+      return false;
+    }
   }
 
   // Warn about having an escaped newline between the */ characters.
   if (!L->isLexingRawMode())
     L->Diag(CurPtr, diag::escaped_newline_block_comment_end);
 
   // If there was space between the backslash and newline, warn about it.
   if (HasSpace && !L->isLexingRawMode())