[PATCH] D148987: [clang][Interp] Check Neg ops for errors

[Timm Bäder via Phabricator via cfe-commits]

tbaeder created this revision.
tbaeder added reviewers: aaron.ballman, erichkeane, tahonermann, shafik.
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tbaeder requested review of this revision.
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I'm not sure what to do with the float case here, maybe it's not relevant at all.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148987

Files:
  clang/lib/AST/Interp/Integral.h
  clang/lib/AST/Interp/Interp.h
  clang/test/AST/Interp/literals.cpp


Index: clang/test/AST/Interp/literals.cpp
===================================================================
--- clang/test/AST/Interp/literals.cpp
+++ clang/test/AST/Interp/literals.cpp
@@ -80,6 +80,12 @@
 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, "");
Index: clang/lib/AST/Interp/Interp.h
===================================================================
--- clang/lib/AST/Interp/Interp.h
+++ clang/lib/AST/Interp/Interp.h
@@ -425,12 +425,35 @@
 
 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;
+  }
 
   S.Stk.push<T>(Result);
-  return true;
+
+  // FIXME: This code Just Works[tm] for floats, but it's probably not doing
+  //   the right thing. At least the diagnostic could be better without
+  //   the conversion to an APInt.
+
+  unsigned Bits = Value.bitWidth();
+  APSInt NegatedValue = -Value.toAPSInt(Bits + 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 {
Index: clang/lib/AST/Interp/Integral.h
===================================================================
--- clang/lib/AST/Interp/Integral.h
+++ clang/lib/AST/Interp/Integral.h
@@ -234,6 +234,9 @@
   }
 
   static bool neg(Integral A, Integral *R) {
+    if (Signed && A.isMin())
+      return true;
+
     *R = -A;
     return false;
   }


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