[clang] [LifeitimeSafety] Support C Language in LifetimeSafety (PR #203270)

[Gábor Horváth via cfe-commits]

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@@ -324,6 +326,10 @@ void FactsGenerator::VisitCastExpr(const CastExpr *CE) {
       flow(Dest, Src, /*Kill=*/true);
     return;
   case CK_ArrayToPointerDecay:
+    // va_arg(ap, array_type) is UB and does not provide addressable array
+    // storage to model.
+    if (isa<VAArgExpr>(SubExpr))
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Xazax-hun wrote:

Did this trigger a crash or a false positive? I wonder if `VAArgExpr` can appear at more places where it can wreak havoc. 

https://github.com/llvm/llvm-project/pull/203270