[clang] [Format] Do not crash on non-null terminated strings (PR #131299)

[Ilya Biryukov via cfe-commits]

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@@ -2382,14 +2382,20 @@ size_t SourceManager::getDataStructureSizes() const {
 
 SourceManagerForFile::SourceManagerForFile(StringRef FileName,
                                            StringRef Content) {
+  // We copy to `std::string` for Context instead of StringRef because the
+  // SourceManager::getBufferData() works only with null-terminated buffers.
+  // And we still want to keep the API convenient.
+  ContentBuffer = Content.str();
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ilya-biryukov wrote:

Is there any particular direction folks want to take this?

Having an API that breaks on non-null-terminated `StringRef` looks but and I don't see **easy** options to fix this other than a copy.

I don't expect this to give any noticeable performance regressions, and I don't have a clear sense of whether the folks in the comment threads agree or disagree.

https://github.com/llvm/llvm-project/pull/131299