[clang] [clang][ExprConst] Reject field access with nullptr base (PR #113885)

[Richard Smith via cfe-commits]

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@@ -1703,7 +1703,7 @@ namespace {
     bool checkNullPointerDiagnosingWith(const GenDiagType &GenDiag) {
       if (Designator.Invalid)
         return false;
-      if (IsNullPtr) {
+      if (getLValueBase().isNull()) {
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zygoloid wrote:

Oh, I see. We're adjusting the offset *before* we call `addDecl`. I think this would be better fixed by reversing the order in which we do those steps -- first `addDecl` and then adjust the offset. A null base isn't necessarily a null pointer, so checking for a null base here seems wrong (but only in the weird case of a zero integer cast to a non-null pointer value, which we should only accept in constant-folding mode, not when properly evaluating).

https://github.com/llvm/llvm-project/pull/113885