llvm-project/clang/test/AST/ByteCode/references.cpp

// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -verify=expected,both %s
// RUN: %clang_cc1 -verify=ref,both %s


constexpr int a = 10;
constexpr const int &b = a;
static_assert(a == b, "");

constexpr int assignToReference() {
  int a = 20;
  int &b = a;

  b = 100;
  return a;
}
static_assert(assignToReference() == 100, "");


constexpr void setValue(int &dest, int val) {
  dest = val;
}

constexpr int checkSetValue() {
  int l = 100;
  setValue(l, 200);
  return l;
}
static_assert(checkSetValue() == 200, "");

constexpr int readLocalRef() {
  int a = 20;
  int &b = a;
  return b;
}
static_assert(readLocalRef() == 20, "");

constexpr int incRef() {
  int a = 0;
  int &b = a;

  b = b + 1;

  return a;
}
static_assert(incRef() == 1, "");


template<const int &V>
constexpr void Plus3(int &A) {
  A = V + 3;
}
constexpr int foo = 4;

constexpr int callTemplate() {
  int a = 3;
  Plus3<foo>(a);
  return a;
}
static_assert(callTemplate() == 7, "");


constexpr int& getValue(int *array, int index) {
  return array[index];
}
constexpr int testGetValue() {
  int values[] = {1, 2, 3, 4};
  getValue(values, 2) = 30;
  return values[2];
}
static_assert(testGetValue() == 30, "");

constexpr const int &MCE = 20;
static_assert(MCE == 20, "");
static_assert(MCE == 30, ""); // both-error {{static assertion failed}} \
                              // both-note {{evaluates to '20 == 30'}}

constexpr int LocalMCE() {
  const int &m = 100;
  return m;
}
static_assert(LocalMCE() == 100, "");
static_assert(LocalMCE() == 200, ""); // both-error {{static assertion failed}} \
                                      // both-note {{evaluates to '100 == 200'}}

struct S {
  int i, j;
};

constexpr int RefToMemberExpr() {
  S s{1, 2};

  int &j = s.i;
  j = j + 10;

  return j;
}
static_assert(RefToMemberExpr() == 11, "");

struct Ref {
  int &a;
};

constexpr int RecordWithRef() {
  int m = 100;
  Ref r{m};
  m = 200;
  return r.a;
}
static_assert(RecordWithRef() == 200, "");


struct Ref2 {
  int &a;
  constexpr Ref2(int &a) : a(a) {}
};

constexpr int RecordWithRef2() {
  int m = 100;
  Ref2 r(m);
  m = 200;
  return r.a;
}
static_assert(RecordWithRef2() == 200, "");

const char (&nonextended_string_ref)[3] = {"hi"};
static_assert(nonextended_string_ref[0] == 'h', "");
static_assert(nonextended_string_ref[1] == 'i', "");
static_assert(nonextended_string_ref[2] == '\0', "");

/// This isa non-constant context. Reading A is not allowed,
/// but taking its address is.
int &&A = 12;
int arr[!&A];

namespace Temporaries {
  struct A { int n; };
  struct B { const A &a; };
  const B j = {{1}}; // both-note {{temporary created here}}

  static_assert(j.a.n == 1, "");  // both-error {{not an integral constant expression}} \
                                  // both-note {{read of temporary is not allowed in a constant expression outside the expression that created the temporary}}
}

namespace Params {
  typedef __SIZE_TYPE__ size_t;

  template <class _Tp, size_t _Np>
  constexpr _Tp* end(_Tp (&__array)[_Np]) noexcept {
    return __array + _Np;
  }


  struct classnames {
    const char* elem_;
    int a;
  };

  constexpr classnames ClassNames[] = {
    {"a", 0},
    {"b", 1},
    {"b", 1},
    {"b", 1},
    {"b", 1},
    {"b", 1},
    {"b", 1},
    {"b", 1},
  };

  constexpr bool foo() {
    /// This will instantiate end() with ClassNames.
    /// In Sema, we will constant-evaluate the return statement, which is
    /// something like __array + 8. The APValue we return for this
    /// may NOT have a LValuePath set, since it's for a parameter
    /// of LValueReferenceType.
    end(ClassNames);
    return true;
  }

  static_assert(foo());
}