c++/8158: Compiler rejects legal default parameter

c++/8158: Compiler rejects legal default parameter

[m.doppler]

>Number:         8158
>Category:       c++
>Synopsis:       Compiler rejects legal default parameter
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Mon Oct 07 05:56:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Michael Doppler, Peter Klotz
>Release:        gcc 3.2, gcc 3.1
>Organization:
>Environment:
Redhat 8.0, gcc 3.2, glibc 2.2.93
Redhat 7.2, gcc 3.1, glibc 2.2.4
>Description:
The following code doesn't compile although it should.

#include <map>

class A
{
public:
typedef std::map<unsigned char,int> TType;
        //A(const TType& x=TType()) // this works
        A( const std::map<unsigned char, int> & p_map = std::map<unsigned char, int>() ) // this doesn't
        {
        }
};

int main(void )
{
        A a;
        return 0;
}
>How-To-Repeat:
Compile program from description.
>Fix:
Workaround: use typedef provided in code snippet.
>Release-Note:
>Audit-Trail:
>Unformatted:

Re: c++/8158: Compiler rejects legal default parameter

[nathan]

Synopsis: Compiler rejects legal default parameter

State-Changed-From-To: open->closed
State-Changed-By: nathan
State-Changed-When: Mon Oct  7 09:42:34 2002
State-Changed-Why:
    not a bug. There is a defect report about this. The
    c++ std does not specify exactly when default args
    of member functions are parsed.
    Your default arg contains an unparenthesized comma.
    It is *very* hard to determine whether a '<' marks
    the start of a template parm list at that point. The
    defect report resolves this by saying the default
    arg consists of the tokens up to the next unparenthesized,
    unbracketed comma or close paren.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8158