[clang] Fix clang crash when printing highlighted code in diagnostic (after #66514) (PR #80442)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (alexfh)

<details>
<summary>Changes</summary>

Implements the fix proposed by Evgeny Eltsin on
https://github.com/llvm/llvm-project/pull/66514#issuecomment-1924039038.

No test case provided, since the bug is extremely sensitive to the preprocessor
state (headers, macros, including the ones defined on command line), and it
turned out to be non-trivial to create an isolated test.


---
Full diff: https://github.com/llvm/llvm-project/pull/80442.diff


1 Files Affected:

- (modified) clang/lib/Frontend/TextDiagnostic.cpp (+1-1) 


``````````diff
diff --git a/clang/lib/Frontend/TextDiagnostic.cpp b/clang/lib/Frontend/TextDiagnostic.cpp
index 627a7641308a1..10240d7ee6f2e 100644
--- a/clang/lib/Frontend/TextDiagnostic.cpp
+++ b/clang/lib/Frontend/TextDiagnostic.cpp
@@ -1349,7 +1349,7 @@ void TextDiagnostic::emitSnippetAndCaret(
   // Prepare source highlighting information for the lines we're about to
   // emit, starting from the first line.
   std::unique_ptr<SmallVector<StyleRange>[]> SourceStyles =
-      highlightLines(BufStart, Lines.first, Lines.second, PP, LangOpts,
+      highlightLines(BufData, Lines.first, Lines.second, PP, LangOpts,
                      DiagOpts->ShowColors, FID, SM);
 
   SmallVector<LineRange> LineRanges =

``````````

</details>


https://github.com/llvm/llvm-project/pull/80442