[clang] [clang][analyzer] Fix argument invalidations in StreamChecker. (PR #79470)

[Balázs Kéri via cfe-commits]

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@@ -763,6 +779,11 @@ void StreamChecker::evalFreadFwrite(const FnDescription *Desc,
     return;
   }
 
+  // At read, invalidate the buffer in any case of error or success,
+  // except if EOF was already present.
+  if (IsFread && (OldSS->ErrorState != ErrorFEof))
+    State = escapeArgs(State, C, Call, {0});
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balazske wrote:

This could be a future improvement (after this patch). I am not sure if this works always correct, because it looks like that the `ElementCount` value at `fread` is used but not the "size" argument (size of one element). It is assumed that the specified element size is always the same as one array element, but this can be different.

https://github.com/llvm/llvm-project/pull/79470