[libc-commits] [libc] Create a poor-developer's msan for libc wide read functions. (PR #170586)

[Michael Jones via libc-commits]

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@@ -0,0 +1,93 @@
+// For performance, some vector-based libc functions read data outside of, but
+// adjacent to, the input address. For example, string_length can read both
+// before and after the data in its src parameter. As part of the
+// implementation, it is allowed to do this. However, the code must take care
+// to avoid address errors. The sanitizers can't distinguish between "the
+// implementation" and user-code, and so report an error. Therefore we can't use
+// them to check if functions like thees have memory errors.
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michaelrj-google wrote:

nit:
```suggestion
// them to check if functions like these have memory errors.
```

https://github.com/llvm/llvm-project/pull/170586