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// RUN: %clang_cc1 -std=c++1y -verify %s -fcxx-exceptions -triple=x86_64-linux-gnu
struct S {
// dummy ctor to make this a literal type
constexpr S(int);
S();
int arr[10];
constexpr int &get(int n) { return arr[n]; }
constexpr const int &get(int n) const { return arr[n]; }
};
S s = S();
const S &sr = s;
static_assert(&s.get(4) - &sr.get(2) == 2, "");
// Compound-statements can be used in constexpr functions.
constexpr int e() {{{{}} return 5; }}
static_assert(e() == 5, "");
// Types can be defined in constexpr functions.
constexpr int f() {
enum E { e1, e2, e3 };
struct S {
constexpr S(E e) : e(e) {}
constexpr int get() { return e; }
E e;
};
return S(e2).get();
}
static_assert(f() == 1, "");
// Variables can be declared in constexpr functions.
constexpr int g(int k) {
const int n = 9;
int k2 = k * k;
int k3 = k2 * k;
return 3 * k3 + 5 * k2 + n * k - 20;
}
static_assert(g(2) == 42, "");
constexpr int h(int n) {
static const int m = n; // expected-error {{static variable not permitted in a constexpr function}}
return m;
}
constexpr int i(int n) {
thread_local const int m = n; // expected-error {{thread_local variable not permitted in a constexpr function}}
return m;
}
// if-statements can be used in constexpr functions.
constexpr int j(int k) {
if (k == 5)
return 1;
if (k == 1)
return 5;
else {
if (int n = 2 * k - 4) {
return n + 1;
return 2;
}
}
} // expected-note 2{{control reached end of constexpr function}}
static_assert(j(0) == -3, "");
static_assert(j(1) == 5, "");
static_assert(j(2), ""); // expected-error {{constant expression}} expected-note {{in call to 'j(2)'}}
static_assert(j(3) == 3, "");
static_assert(j(4) == 5, "");
static_assert(j(5) == 1, "");
// There can be 0 return-statements.
constexpr void k() {
}
// If the return type is not 'void', no return statements => never a constant
// expression, so still diagnose that case.
[[noreturn]] constexpr int fn() { // expected-error {{no return statement in constexpr function}}
fn();
}
// We evaluate the body of a constexpr constructor, to check for side-effects.
struct U {
constexpr U(int n) {
if (j(n)) {} // expected-note {{in call to 'j(2)'}}
}
};
constexpr U u1{1};
constexpr U u2{2}; // expected-error {{constant expression}} expected-note {{in call to 'U(2)'}}
// We allow expression-statements.
constexpr int l(bool b) {
if (b)
throw "invalid value for b!"; // expected-note {{subexpression not valid}}
return 5;
}
static_assert(l(false) == 5, "");
static_assert(l(true), ""); // expected-error {{constant expression}} expected-note {{in call to 'l(true)'}}
// Potential constant expression checking is still applied where possible.
constexpr int htonl(int x) { // expected-error {{never produces a constant expression}}
typedef unsigned char uchar;
uchar arr[4] = { uchar(x >> 24), uchar(x >> 16), uchar(x >> 8), uchar(x) };
return *reinterpret_cast<int*>(arr); // expected-note {{reinterpret_cast is not allowed in a constant expression}}
}
constexpr int maybe_htonl(bool isBigEndian, int x) {
if (isBigEndian)
return x;
typedef unsigned char uchar;
uchar arr[4] = { uchar(x >> 24), uchar(x >> 16), uchar(x >> 8), uchar(x) };
return *reinterpret_cast<int*>(arr); // expected-note {{reinterpret_cast is not allowed in a constant expression}}
}
constexpr int swapped = maybe_htonl(false, 123); // expected-error {{constant expression}} expected-note {{in call}}
namespace NS {
constexpr int n = 0;
}
constexpr int namespace_alias() {
namespace N = NS;
return N::n;
}
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