[clang] [clang] Implement -Walloc-size diagnostic option (PR #150028)

[Erich Keane via cfe-commits]

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@@ -717,6 +717,10 @@ Improvements to Clang's diagnostics
   Added a new warning in this group for the case where the attribute is missing/implicit on
   an override of a virtual method.
 
+- A new warning ``-Walloc-size`` has been added to detect calls to functions
+  decorated with the ``alloc_size`` attribute don't allocate enough space for
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erichkeane wrote:

```suggestion
  decorated with the ``alloc_size`` attribute that don't allocate enough space for
```

https://github.com/llvm/llvm-project/pull/150028