[clang] [analyzer][NFCI] Move the core.FixedAddressDereference checker to optin.core (PR #181858)

[Donát Nagy via cfe-commits]

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@@ -1,4 +1,4 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core -verify %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core.FixedAddr,optin.core.FixedAddressDereference -verify %s
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NagyDonat wrote:

Yes, `alpha.core.FixedAddr` is bad and should be removed.

The initial goal of this project (which was done by @balazske) was that our team wanted to make `alpha.core.FixedAddr` ready for production, then it turned out that instead of improving its original implementation it is better to build onto the implementation of `core.NullDereference`. Now that there is a stable checker for detecting this kind of issue, there is no reason to keep `alpha.core.FixedAddr` and our team will shortly create a PR to remove it.

https://github.com/llvm/llvm-project/pull/181858