[Bug c++/13156] New: Greedy instantiation

[Bug c++/13156] New: Greedy instantiation

[dave at boost-consulting dot com]

The following fails to compile, but shouldn't.  You can see this by replacing 
the body of X's constructor with ";", which will cause compilation to succeed.

------

struct X
{
    template <class T>
    X(T const&) { T x = 1; }
};

template <class From, class To>
struct conv
{
    
    static char (& _m_check(...) )[2];
    static char _m_check(To);
    static From _m_from;

    enum {
        value = sizeof( _m_check(_m_from) ) == 1
    };
};

int x[conv<char*,X>::value ? 1 : -1];

-- 
           Summary: Greedy instantiation
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dave at boost-consulting dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13156

[Bug c++/13156] Greedy instantiation

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-21 18:50 -------
Actually it should fail as:
        value = sizeof( _m_check(_m_from) ) == 1

is you cannot use _m_check or _m_from here because the struct is defined as undefined at this 
point.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13156

[Bug c++/13156] Greedy instantiation

[dave at boost-consulting dot com]

------- Additional Comments From dave at boost-consulting dot com  2003-11-21 19:13 -------
Well, you're wrong about that, but even if you weren't:

------

struct X
{
    template <class T>
    X(T const&) { T x = 1; }
};

template <class From, class To>
struct conv1
{
    
    static char (& _m_check(...) )[2];
    static char _m_check(To);
    static From _m_from;
};

template <class From, class To>
struct conv
{
    enum {
        value = sizeof( conv1<From,To>::_m_check(conv1<From,To>::_m_from) ) == 
1
    };
};

int x[conv<char*,X>::value ? 1 : -1];


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13156

[Bug c++/13156] Greedy instantiation

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-21 19:42 -------
That is already fixed on the mainline and since this is not a regression, it will not be back ported 
back to 3.3.x.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13156