[clang] [docs][msan] List common cases reported by msan (PR #101105)

[John Stiles via cfe-commits]

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@@ -8,11 +8,18 @@ MemorySanitizer
 Introduction
 ============
 
-MemorySanitizer is a detector of uninitialized reads. It consists of a
+MemorySanitizer is a detector of uninitialized memory use. It consists of a
 compiler instrumentation module and a run-time library.
 
 Typical slowdown introduced by MemorySanitizer is **3x**.
 
+Here is a not comprehensive of list cases when MemorySanitizer will report an error:
+
+* Uninitialized value was used in a conditional branch.
+* Uninitialized pointer was used for memory accesses.
+* Uninitialized value passed or returned from a function call, which is considered an undefined behavior. The check can be disabled with ``-fno-sanitize-memory-param-retval``.
+* Uninitialized data was passed into some libc calls.
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johnstiles-google wrote:

Is this redundant with "Uninitialized value passed or returned from a function call"?

https://github.com/llvm/llvm-project/pull/101105