[clang][Interp] Check Neg ops for errors

This should fail when negating __INT_MIN__. Differential Revision: https://reviews.llvm.org/D148987
llvm · Apr 27, 2023 · 6cf14a7 · 6cf14a7
1 parent 8babf8f
commit 6cf14a7
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Showing 4 changed files with 34 additions and 3 deletions.
diff --git a/clang/lib/AST/Interp/Integral.h b/clang/lib/AST/Interp/Integral.h
@@ -223,6 +223,9 @@ template <unsigned Bits, bool Signed> class Integral final {
   }
 
   static bool neg(Integral A, Integral *R) {
+    if (Signed && A.isMin())
+      return true;
+
     *R = -A;
     return false;
   }

diff --git a/clang/lib/AST/Interp/Interp.h b/clang/lib/AST/Interp/Interp.h
@@ -413,12 +413,32 @@ bool Inv(InterpState &S, CodePtr OpPC) {
 
 template <PrimType Name, class T = typename PrimConv<Name>::T>
 bool Neg(InterpState &S, CodePtr OpPC) {
-  const T &Val = S.Stk.pop<T>();
+  const T &Value = S.Stk.pop<T>();
   T Result;
-  T::neg(Val, &Result);
 
+  if (!T::neg(Value, &Result)) {
+    S.Stk.push<T>(Result);
+    return true;
+  }
+
+  assert(isIntegralType(Name) &&
+         "don't expect other types to fail at constexpr negation");
   S.Stk.push<T>(Result);
-  return true;
+
+  APSInt NegatedValue = -Value.toAPSInt(Value.bitWidth() + 1);
+  const Expr *E = S.Current->getExpr(OpPC);
+  QualType Type = E->getType();
+
+  if (S.checkingForUndefinedBehavior()) {
+    SmallString<32> Trunc;
+    NegatedValue.trunc(Result.bitWidth()).toString(Trunc, 10);
+    auto Loc = E->getExprLoc();
+    S.report(Loc, diag::warn_integer_constant_overflow) << Trunc << Type;
+    return true;
+  }
+
+  S.CCEDiag(E, diag::note_constexpr_overflow) << NegatedValue << Type;
+  return S.noteUndefinedBehavior();
 }
 
 enum class PushVal : bool {

diff --git a/clang/lib/AST/Interp/PrimType.h b/clang/lib/AST/Interp/PrimType.h
@@ -42,6 +42,8 @@ enum PrimType : unsigned {
   PT_FnPtr,
 };
 
+constexpr bool isIntegralType(PrimType T) { return T <= PT_Uint64; }
+
 /// Mapping from primitive types to their representation.
 template <PrimType T> struct PrimConv;
 template <> struct PrimConv<PT_Sint8> { using T = Integral<8, true>; };

diff --git a/clang/test/AST/Interp/literals.cpp b/clang/test/AST/Interp/literals.cpp
@@ -80,6 +80,12 @@ static_assert(~255 == -256, "");
 static_assert(~INT_MIN == INT_MAX, "");
 static_assert(~INT_MAX == INT_MIN, "");
 
+static_assert(-(1 << 31), ""); // expected-error {{not an integral constant expression}} \
+                               // expected-note {{outside the range of representable values}} \
+                               // ref-error {{not an integral constant expression}} \
+                               // ref-note {{outside the range of representable values}} \
+
+
 enum E {};
 constexpr E e = static_cast<E>(0);
 static_assert(~e == -1, "");