[Clang] Fix crash caused by line splicing in doc comment

[cor3ntin]

Summary

Because the comment parser does not support slices,
we emit a warning for comments that do contain
a splice within their delimiter, and do not add them as
documentation comment.

Fixes #62054

[cor3ntin]

Add release note

[shafik]

Do we have a test that covers valid doxygen comments? I was looking and I don't see an obvious one.

[shafik]

clang/lib/Sema/Sema.cpp

2404

I don't get why we don't have to handle the other RawComment cases here.

[cor3ntin]

In D148029#4258800, @shafik wrote:

Do we have a test that covers valid doxygen comments? I was looking and I don't see an obvious one.

AFAICT, some in CommentTextTest.cpp - not that many though.

clang/lib/Sema/Sema.cpp

2404

Because they can't be isAlmostTrailingComment - which checks whether you forgot an additional * or /

[aaron.ballman]

clang/include/clang/AST/RawCommentList.h

122

Just to double-check, we don't have to worry about there being leading whitespace in Text do we?

[cor3ntin]

clang/include/clang/AST/RawCommentList.h

122

Afaict, we always have a valid comment, starting with / (and ending with / for a multi line comment). We might not have a comment valid for documentation purposes.

[aaron.ballman]

The changes seem reasonable to me.

clang/include/clang/AST/RawCommentList.h

122

Excellent -- I was poking around and it seemed like we do trim the text before forming the comment object, so yay.

[shafik]

LGTM

clang/docs/ReleaseNotes.rst

 - Fix crash when generating code coverage information for `PseudoObjectExpr` in 
   Clang AST.
   (`#45481 <https://github.com/llvm/llvm-project/issues/45481>`_)
 - Fix the assertion hit when a template consteval function appears in a nested
   consteval/constexpr call chain.
   (`#61142 <https://github.com/llvm/llvm-project/issues/61142>`_)
 - Clang now better diagnose placeholder types constrained with a concept that is
   not a type concept.
+- Fix crash when a doc comment contains a line splicing.
+  (`#62054 <https://github.com/llvm/llvm-project/issues/62054>`_)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Bug Fixes to Attribute Support
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Bug Fixes to C++ Support

clang/include/clang/AST/RawCommentList.h

public:
 
   const char *getBriefText(const ASTContext &Context) const {
     if (BriefTextValid)
       return BriefText;
 
     return extractBriefText(Context);
   }
 
+  bool hasUnsupportedSplice(const SourceManager &SourceMgr) const {
+    if (!isInvalid())
+      return false;
+    StringRef Text = getRawText(SourceMgr);
+    if (Text.size() < 6 || Text[0] != '/')
+      return false;
+    if (Text[1] == '*')
+      return Text[Text.size() - 1] != '/' || Text[Text.size() - 2] != '*';
+    return Text[1] != '/';
+  }
+
   /// Returns sanitized comment text, suitable for presentation in editor UIs.
   /// E.g. will transform:
   ///     // This is a long multiline comment.
   ///     //   Parts of it  might be indented.
   ///     /* The comments styles might be mixed. */
   ///  into
   ///     "This is a long multiline comment.\n"
   ///     "  Parts of it  might be indented.\n"

clang/include/clang/Basic/DiagnosticSemaKinds.td

 def err_coro_invalid_addr_of_label : Error<
   "the GNU address of label extension is not allowed in coroutines."
 >;
 } // end of coroutines issue category
 
 let CategoryName = "Documentation Issue" in {
 def warn_not_a_doxygen_trailing_member_comment : Warning<
   "not a Doxygen trailing comment">, InGroup<Documentation>, DefaultIgnore;
+def warn_splice_in_doxygen_comment : Warning<
+  "line splicing in Doxygen comments are not supported">, InGroup<Documentation>, DefaultIgnore;
 } // end of documentation issue category
 
 let CategoryName = "Nullability Issue" in {
 
 def warn_mismatched_nullability_attr : Warning<
   "nullability specifier %0 conflicts with existing specifier %1">,
   InGroup<Nullability>;
 

clang/lib/Sema/Sema.cpp

 }
 
 
 void Sema::ActOnComment(SourceRange Comment) {
   if (!LangOpts.RetainCommentsFromSystemHeaders &&
       SourceMgr.isInSystemHeader(Comment.getBegin()))
     return;
   RawComment RC(SourceMgr, Comment, LangOpts.CommentOpts, false);
-  if (RC.isAlmostTrailingComment()) {
+  if (RC.isAlmostTrailingComment() || RC.hasUnsupportedSplice(SourceMgr)) {
     SourceRange MagicMarkerRange(Comment.getBegin(),
                                  Comment.getBegin().getLocWithOffset(3));
     StringRef MagicMarkerText;
     switch (RC.getKind()) {
     case RawComment::RCK_OrdinaryBCPL:
       MagicMarkerText = "///<";
       break;
     case RawComment::RCK_OrdinaryC:
       MagicMarkerText = "/**<";
       break;
+    case RawComment::RCK_Invalid:
+      // FIXME: are there other scenarios that could produce an invalid
+      // raw comment here?
+      Diag(Comment.getBegin(), diag::warn_splice_in_doxygen_comment);
+      return;
     default:
       llvm_unreachable("if this is an almost Doxygen comment, "
                        "it should be ordinary");
     }
     Diag(Comment.getBegin(), diag::warn_not_a_doxygen_trailing_member_comment) <<
       FixItHint::CreateReplacement(MagicMarkerRange, MagicMarkerText);
   }
   Context.addComment(RC);

clang/test/Lexer/comment-escape.c

-// RUN: %clang -fsyntax-only %s 
+// RUN: %clang -fsyntax-only -Wdocumentation %s
 // rdar://6757323
 // foo \
 
 #define blork 32
 
+// GH62054
+
+/**<*\
+/
+//expected-warning@-2 {{escaped newline between}} \
+//expected-warning@-2 {{line splicing in Doxygen comments are not supported}}
+
+/**<*\ 
+/
+//expected-warning@-2 {{escaped newline between}} \
+//expected-warning@-2 {{backslash and newline separated by space}} \
+//expected-warning@-2 {{line splicing in Doxygen comments are not supported}}
+
+
+/*<*\
+/
+//expected-warning@-2 {{escaped newline between}}  \
+//expected-warning@-2 {{line splicing in Doxygen comments are not supported}}
+
+/*<*\  
+/
+//expected-warning@-2 {{escaped newline between}} \
+//expected-warning@-2 {{backslash and newline separated by space}} \
+//expected-warning@-2 {{line splicing in Doxygen comments are not supported}}
+
+/\
+*<**/
+//expected-warning@-2 {{line splicing in Doxygen comments are not supported}}
+
+/\
+/<*
+//expected-warning@-2 {{line splicing in Doxygen comments are not supported}}