c++/9666: Arg conversion problem with operator new

c++/9666: Arg conversion problem with operator new

[BrainChild]

>Number:         9666
>Category:       c++
>Synopsis:       Arg conversion problem with operator new
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Feb 11 20:46:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Don Stauffer
>Release:        3.2
>Organization:
>Environment:
Cygwin under Windows 2000 Professional
>Description:
g++ produces error "size in array new must have integral type" if you use new[] with an argument of a class with two integral conversion operators which are identical exception one is a const method.  The conversion works if used to pass the class object as a size_t function argument, and works with new if you remove either one of the conversion operators.
>How-To-Repeat:
#include	<cstddef>

struct	X
{
	operator size_t	()				{	return
2;	}
	operator size_t	()	const	{	return	3;	}
};

char	*f1	(	size_t	n	)		{	return
new	char[n];	}

char	*f2	(	const X	&x	)	{	return	new
char[x];	}

int	main	(void)					{	}

/*

$ g t.cpp -ot
t.cpp: In function `char* f2(const X&)':
t.cpp:11: size in array new must have integral type

*/
>Fix:
Workaround: Call a function which converts the argument and allocates the memory rather than calling new directly.
>Release-Note:
>Audit-Trail:
>Unformatted:

Re: c++/9666: Arg conversion problem with operator new

[bangerth]

Synopsis: Arg conversion problem with operator new

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Fri Feb 14 21:22:28 2003
State-Changed-Why:
    Confirmed -- well, sort of, since I am not sure whether this
    is legal. Here's the code slightly reformatted:
    -------------------------
    #include        <cstddef>
    
    struct  X {
        operator size_t ();
        operator size_t () const;
    };
    
    char *f2 (const X &x) { return new char[x]; }
    --------------------------
    The compiler complains:
    tmp/g> /home/bangerth/bin/gcc-3.4-pre/bin/c++ -c x.cc
    x.cc: In function `char* f2(const X&)':
    x.cc:8: error: expression in new-declarator must have integral or enumeration
       type
    
    Now, I tend to think that the code is illegal, due to 5.3.4.7:
    7 Every constant-expression in a direct-new-declarator shall be an inte-
      gral  constant  expression  (_expr.const_)  and evaluate to a strictly
      positive value.  The expression in a direct-new-declarator shall  have
      integral type (_basic.fundamental_) with a non-negative value.
    
    
    Then, on the other hand, this code compiles:
    -----------------------
    #include        <cstddef>
    
    struct  X {
    /*  operator size_t (); */
        operator size_t () const;
    };
    
    char *f2 (const X &x) { return new char[x]; }
    -----------------------
    I should think that the presence of the second non-const 
    operator shouldn't make a difference since x is a constant
    reference...
    
    Can someone clarify?
    
    W.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9666