[clang][Interp] Fix nullptr - nullptr expressions

They can happen and we used to run into an assertion.
llvm · Feb 19, 2024 · 17a1b8f · 17a1b8f
1 parent 8d8bb35
commit 17a1b8f
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diff --git a/clang/lib/AST/Interp/Interp.h b/clang/lib/AST/Interp/Interp.h
@@ -1579,6 +1579,11 @@ inline bool SubPtr(InterpState &S, CodePtr OpPC) {
     return false;
   }
 
+  if (LHS.isZero() && RHS.isZero()) {
+    S.Stk.push<T>();
+    return true;
+  }
+
   T A = T::from(LHS.getIndex());
   T B = T::from(RHS.getIndex());
   return AddSubMulHelper<T, T::sub, std::minus>(S, OpPC, A.bitWidth(), A, B);

diff --git a/clang/test/AST/Interp/literals.cpp b/clang/test/AST/Interp/literals.cpp
@@ -1124,3 +1124,10 @@ namespace rdar8769025 {
     f1(0); // both-warning{{null passed to a callee that requires a non-null argument}}
   }
 }
+
+namespace nullptrsub {
+  void a() {
+    char *f = (char *)0;
+    f = (char *)((char *)0 - (char *)0);
+  }
+}