<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJytVlFvozgQ_jXkZbSI2JSUhzzQtF2ddNpb3a5O97YyYBL3HBzZpt3ur78ZQwJJk-5W3Yi6YMYz33zj-XBp6uflyrRO1dKC3ygHEbvGe_Uoa2is2eKkhDu1li1oVVphnyO2Ai-dR4Mn5TdQadGuYc7jJE5AtPV-gkUsj5LbKCmGMUuGKzw6b7vKw03Eb46sGK9lo1oJq78-ffl69-_nv6FCgF5-39nzJv8Ufw4mj0JPfQ0hCogWQ4xdV2pVRXwwAPyNYdDxNWIma9h-Q18Q8VuYI0Ccur20IkSmuwwMcmVfegjTcXimZM-7ihZ3k_hkdMzLsbVqPZC7EbCVvrMt7KOMiMfltOiA4qLrGzA7aYU3NuIrutg1LqRaHla9ALev5Ug0-QycbL-Jg_FJIPQcTKxsQha8CNbsej-xuETWTWB7D5MNGEGN3It45F8RHwM_EStol79SUyzEzYRX3GfKbWTdT722F05Mj6sijmvygsEp_wXtT16cK8MhxRHBcZ7j_BC6z6VP-qSGL8JTI1GQZkh2sJyWFAQ9h8L1SQZw2CQoCowGTkOKr-IT5iYpT-CJ-LCNL2EjROuLiAY_zes-TrSnHz-aujTao661_wG2qKQduPF-56gA7B6vdW8SG4sI7n_gX_vQfG_yh89XU0-Fg2fTQSVacFIih_BxhRVbOKJT2q2slfASTOd3nSeCaJMBiq3QT-LZ4UKtUU5L2RgrgxTE8Ek-SovKoaVztKRX1Z1Fj27oOtPZCkHfIdw0xQElFzOQ1tKmKYJX8GbURmi6tvLKUBsskLEFQWiNB9HbCGSaZBYjotFPOYbxF13dDXzw1RTWnBM2GihOINhKUYNpwJQPEjUDOaGPDyjvsBCN9GorD7C0Nk_IC_L5E4S_UZJ_7XcpYWSIF3wxTRjR7yuBlBdj84Rr8V4teRdaAsrYZbRI4Wmnf8ClJ619Pom3CekvY-bE8Dx5M-YRzhHe36dor6Ke9Od51M0ZbG_ou-lcP4GL_qATHWpbLx3YVE_W4E2QOsyp7Dw1YoUwnYR1VcFWPKMIwVp6r9CQjn617D_upBrG0ikxOIkR0Kxe8jrnuZiJzm-MXX41pfpSbXSHmjfrrF6eiCmeFrsyrswWH7R-3P_7sLOGtAAflXOdRLm7v-Jpns42S9Zk1ULkaZYkLJtXdcrnVc6rmmcsL7Msm2lRSu2W0RXWkLXyCYILvI-ubmfvR6CWLGEsmfN5kqZzxuM8yTPGkyzPRcqbkkVpIrdC6Zj80HdiZpfBZdmtHb7Uynk3vhQoXOtWygAYEXrltVz2BcJPx9bRdsASGBT_H1Jo07n-lH3QxiDvLuye_bF4FkAvA-L_AWOgPAY>53494</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang seems to be overzealous with lifetime errors in constexpr
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          TobiSchluter
      </td>
    </tr>
</table>

<pre>
    Consider this (derived from the Eigen library, tested with clang 13.0.0 and clang 12)

```
struct B;

#define CONSTEXPR constexpr
#define CONSTEVAL consteval

struct A {
public:
    CONSTEXPR A() { m_val = 1; }
    CONSTEXPR A(const A& other) { m_val = other.m_val;}
    CONSTEXPR ~A() {};

    CONSTEXPR int val() { return m_val; }

    int m_val;

    CONSTEXPR B operator<<(int);
};

struct B {
    A& m_a;
    CONSTEXPR B(A& ref) : m_a(ref) {}
    CONSTEXPR B& operator,(int i) { m_a.m_val = i; return *this; }
    CONSTEXPR ~B() { finished(); }
    CONSTEXPR A finished() { return m_a; }
};

CONSTEXPR B A::operator<<(int i) {
    m_val = i;
    return B(*this);
}

CONSTEVAL int f()
{
    A a{(A() << 1, 2, 3, 4).finished()};
    return a.val();
}

int g()
{
    return f();
}

```

Godbolt link here: https://godbolt.org/z/njfxf9jP5

As you can see in GCC's intermediate output, ~B is always called before ~A. Nevertheless, clang prints
source>:44:12: error: call to consteval function 'f' is not a constant expression
    return f();
           ^
<source>:13:43: note: read of object outside its lifetime is not allowed in a constant expression
    CONSTEXPR A(const A& other) { m_val = other.m_val;}
                                          ^
<source>:28:37: note: in call to 'A(A())'
    CONSTEXPR A finished() { return m_a; }
                                    ^
<source>:27:22: note: in call to '&A() << 1->finished()'
    CONSTEXPR ~B() { finished(); }
                     ^
<source>:38:10: note: in call to '&A() << 1->~B()'
    A a{(A() << 1, 2, 3, 4).finished()};
         ^
<source>:44:12: note: in call to 'f()'
    return f();
           ^
           
 (I think clang is wrong here, but of course gcc may be getting the destruction order wrong.)
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJytVl2PmzoQ_TXkZVREcL544IFks1Wlq97qtrq6b5UBk3jr4Mg2m6a__s4YEkg22XbVIuKAGc-cOeM5kOvymK50bWUpDLittBDEC7yWz6KEyugdTgpYy42oQcnccHMM4hU4YR0aHKTbQqF4vYExC6MwAl6Xp4k4iJMgegiirBtnUXf6W-tMUzhYBmx5YRWzUlSyFrD6--PnL-v_Pv0DBQJ04vve3Db5N_urM3nmauirC5FBMO9i7JtcySJgnQHg0YdBxwvETNaw-4q-IGAPMEaAOPVwb4WPTFcz0MiVeenBT4f-npK97SqYrwfxyeiSl0trWTsgdz1gI1xjajhF6RH3y2nRGcVd10vQe2G40yZgKzrjBS6kWp5XvQB3qmVPNPn0nOy-8rPxVSD07E2MqHwWLPPW8eI0Mb9H1tKzfYIZdxhB9tzzsOdfEh8dP0Gc0S5_paZYiOWAV9xn0m5F2U69theuTC-rwi9r8oLBIf8Z7U-W3SrDOcUewWWe_XwXus2lTfqqhi_CUyNRkKpLtrMclhQ43fvCtUl6cNgkKAoxDYyGCT4Kr5gbpDyAx8PzNr6HjRBt7iLq_FSv-7jSnnZ8r8tcK4e6Vn8DbFFBO3Dr3N5SAeJHPDetSagNInj8gb_6qfpeJU-fpkNPmYWjbqDgNVghkEN4v8KKzS3RKcxOlJI7Abpx-8YRQbTJAMWWqwM_WlyoFMppLipthJeCED6KZ2FQOZSwlpa0qro36NF2XacbUyDoNcKdTHBAycUMhDG0aTLvFZzutRGqpi6c1NQGc2RsThBq7YC3NhyZJpnFiGj0U46hP4LpuuODrYawxoyw0UBxPMFG8BJ0BTp_EqgZyAm9fEA6i4WohJM7cYallD4gL8jnTxD-QUn-teNewsgQy9h8mDCiP1UCKc_65vHn_He15LfQEtA4vo8WKbzu9He49Kq1byfxNiH9ZcyMGB5Hb8bcw7nA--cU7VXUg_68jbq6ge0NfTecaydw0Qf6okNta6UDm-pgNF54qcOc8sZRIxYI0wrYFAXs-BFFCDbCOYmG9OlXivblTqqhDX0leichAhqVKSsTlvCRk06JtA2DArizlBQ60ihhPwRXurHtt-K5w71IWc_B6eNu1BiVXskvrmnysNA7vFHq-fT3bm80qQfeSmsbgQL5OGWTZDLapgmbzSNR5FPB8KiSWZVE0zJajGeLspzN2EjxXCibBlOselyLA3gXeB1MH0YyjaM4jsZsHE0m45iFSZTMYhbNkoRPWJXHwSQSOy5VSDjovTAyqYeUNxuLD5W0zvYPOQrVphbCh0P_vHFbbdIvOpefi61q8O0w8vFTj_9_oZcmoA">