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

[Donát Nagy via cfe-commits]

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

This is not what I meant -- sorry if my suggestion wasn't clear enough.

What I wanted to suggest is that it would be nice to have an extra testcase which is similar to the others but does produce an `alpha.unix.cstring.OutOfBounds` report (to demonstrate e.g. that the checker is active).

The `debug.ExprInspection` checks that you added are apparently disconnected from the main goal of this test (I can't imagine a situation where they would be valuable for diagnosing problems introduced by a plausible future code change), so I'd prefer reverting the commit which adds them.

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