Static analyzer HTML output has incorrect links to "note" diagnostics

[nicolas17]

When the clang static analyzer outputs HTML reports, there is a "Bug Summary" section at the top, which has in-page anchor links to the diagnostics in the source file below. When the checker generates "notes" with BugReport.addNote, this section has links to every note in the report.

However, these links are off by one. The first link doesn't work, the second link points at the first note, the third link points at the second note, etc.

To reproduce:

struct A {
  int *iptr;
  int a;
  int b;
  int *c;
  int *d;

  A (int *iptr) : iptr(iptr) {}
};

void f() {
  A a(0);
}

clang --analyze --analyzer-output html -Xanalyzer -analyzer-checker=optin.cplusplus.UninitializedObject test-notes.cpp

The output HTML has links to #EndPath, #Note0, #Note1, #Note2, #Note3 (generated by HTMLDiagnostics::FinalizeHTML), but the notes themselves have id="Note1", id="Note2", id="Note3", id="Note4" (generated by RewriteFile and HandlePiece).

It looks like FinalizeHTML generates the links in incremental order from 0, but RewriteFile is iterating over the notes in reverse order and starts at n (not n-1).

[nicolas17]

Now I see that path-sensitive diagnostic elements start at id="Path1", so probably note IDs should also start at 1. Maybe:

diff --git a/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp b/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
index 0fe0c93dc016..f91a51cc5f8f 100644
--- a/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
+++ b/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
@@ -592,11 +592,11 @@ void HTMLDiagnostics::FinalizeHTML(const PathDiagnostic& D, Rewriter &R,
             P->getLocation().asLocation().getExpansionLineNumber();
         int ColumnNumber =
             P->getLocation().asLocation().getExpansionColumnNumber();
+        ++NumExtraPieces;
         os << "<tr><td class=\"rowname\">Note:</td><td>"
            << "<a href=\"#Note" << NumExtraPieces << "\">line "
            << LineNumber << ", column " << ColumnNumber << "</a><br />"
            << P->getString() << "</td></tr>";
-        ++NumExtraPieces;
       }
     }
 

[llvmbot]

@llvm/issue-subscribers-clang-static-analyzer

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Assign the issue to you.
2. Fix the issue locally.
3. Run the test suite locally.
   3.1) Remember that the subdirectories under test/ create fine-grained testing targets, so you can
   e.g. use make check-clang-ast to only run Clang's AST tests.
4. Create a git commit
5. Run git clang-format HEAD~1 to format your changes.
6. Submit the patch to Phabricator.
   6.1) Detailed instructions can be found here

For more instructions on how to submit a patch to LLVM, see our documentation.

If you have any further questions about this issue, don't hesitate to ask via a comment on this Github issue.

@llvm/issue-subscribers-good-first-issue

[gruuprasad]

@EugeneZelenko @nicolas17 I would like to fix this. Please assign this to me.