[clang] [analyzer] Avoid unnecessary super region invalidation in `CStringChecker` (PR #146212)

[via cfe-commits]

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@@ -0,0 +1,106 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -verify %s
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flovent wrote:

> As a sanity check it would be nice to have a testcase that actually produces some diagnostics.

I add `debug.ExprInspection` to detect if a simple member(`int b`) has it original value after these str functions call, do you have other kind of testcases in mind? I can add it too.

https://github.com/llvm/llvm-project/pull/146212