* Inconsisten error messages on const pointers
@ 2012-10-14 21:34 Arthur Schwarz
2012-10-14 21:56 ` Jonathan Wakely
0 siblings, 1 reply; 3+ messages in thread
From: Arthur Schwarz @ 2012-10-14 21:34 UTC (permalink / raw)
To: gcc-help
In the example below the following two statements seem to be inconsistent:
1: cout << " " << endl << cell1->dump();
2: this->message += cell1->dump();
1: produces the error message
SlipException.h: In member function ‘void slip::SlipException::log()’:
In file included from SlipCell.h:49:0,
from SlipDatum.h:269,
from SlipOp.h:22,
from SlipStringOp.h:12,
from SlipStringOP.cpp:11:
SlipException.h:29:79: error: passing ‘const slip::SlipCellBase’ as ‘this’
argument of ‘virtual std::string slip::SlipCellBase::dump()’ discards qualifiers
With 2: there is no diagnostic message. Any reason why?
===============================================================
[code]
# include <exception>
# include <string>
# include <iostream>
# include <stdlib.h>
# include "SlipDef.h"
# include "SlipErr.h"
# include "SlipCellBase.h"
namespace slip {
class SlipException : public exception {
private:
void log() { cout << "error " << message;
SlipCellBase* castCell1 = const_cast<SlipCellBase*>(cell1);
SlipCellBase* castCell2 = const_cast<SlipCellBase*>(cell2);
if (cell1 != NULL) cout << " " << endl <<
cell1->dump(); // error
if (cell2 != NULL) cout << " " << endl <<
castCell2->dump();
cout << endl << flush;
}
protected:
const SlipCellBase* cell1;
const SlipCellBase* cell2;
string message;
SlipException() { };
public:
SlipException(SlipErr::Error message, SlipCellBase* cell1)
: message(constructMessage(message, "", ""))
, cell1(cell1)
, cell2(NULL) {
this->message += cell1->dump(); // no error
log();
}; // SlipException(SlipErr::Error message, SlipCellBase* cell1)
virtual const char* what() const throw() {
return message.c_str();
}; // virtual const char* what() const throw();
~SlipException() throw() { }
}; // class SlipException
[/code]
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Inconsisten error messages on const pointers
2012-10-14 21:34 Inconsisten error messages on const pointers Arthur Schwarz
@ 2012-10-14 21:56 ` Jonathan Wakely
2012-10-15 6:51 ` Arthur Schwarz
0 siblings, 1 reply; 3+ messages in thread
From: Jonathan Wakely @ 2012-10-14 21:56 UTC (permalink / raw)
To: Arthur Schwarz; +Cc: gcc-help
On 14 October 2012 21:33, Arthur Schwarz wrote:
> In the example below the following two statements seem to be inconsistent:
> 1: cout << " " << endl << cell1->dump();
> 2: this->message += cell1->dump();
>
> 1: produces the error message
> SlipException.h: In member function ‘void slip::SlipException::log()’:
> In file included from SlipCell.h:49:0,
> from SlipDatum.h:269,
> from SlipOp.h:22,
> from SlipStringOp.h:12,
> from SlipStringOP.cpp:11:
> SlipException.h:29:79: error: passing ‘const slip::SlipCellBase’ as ‘this’
> argument of ‘virtual std::string slip::SlipCellBase::dump()’ discards qualifiers
>
> With 2: there is no diagnostic message. Any reason why?
In 1 'cell1' refers to this->cell1 which is a const SlipCellBase*, so
you can't call the non-const dump function
In 2 'cell1' refers to the constructor argument, which has type
SlipCellBase*, so you can call the non-const function.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Inconsisten error messages on const pointers
2012-10-14 21:56 ` Jonathan Wakely
@ 2012-10-15 6:51 ` Arthur Schwarz
0 siblings, 0 replies; 3+ messages in thread
From: Arthur Schwarz @ 2012-10-15 6:51 UTC (permalink / raw)
To: Jonathan Wakely; +Cc: gcc-help
Jonathon;
There is a indentation in my forhead where I said "I knew that".
thanks
art
----- Original Message ----
From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: Arthur Schwarz <aschwarz1309@att.net>
Cc: gcc-help@gcc.gnu.org
Sent: Sun, October 14, 2012 2:20:21 PM
Subject: Re: Inconsisten error messages on const pointers
On 14 October 2012 21:33, Arthur Schwarz wrote:
> In the example below the following two statements seem to be inconsistent:
> 1: cout << " " << endl << cell1->dump();
> 2: this->message += cell1->dump();
>
> 1: produces the error message
> SlipException.h: In member function ‘void slip::SlipException::log()’:
> In file included from SlipCell.h:49:0,
> from SlipDatum.h:269,
> from SlipOp.h:22,
> from SlipStringOp.h:12,
> from SlipStringOP.cpp:11:
> SlipException.h:29:79: error: passing ‘const slip::SlipCellBase’ as ‘this’
> argument of ‘virtual std::string slip::SlipCellBase::dump()’ discards
>qualifiers
>
> With 2: there is no diagnostic message. Any reason why?
In 1 'cell1' refers to this->cell1 which is a const SlipCellBase*, so
you can't call the non-const dump function
In 2 'cell1' refers to the constructor argument, which has type
SlipCellBase*, so you can call the non-const function.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-10-14 21:34 Inconsisten error messages on const pointers Arthur Schwarz
2012-10-14 21:56 ` Jonathan Wakely
2012-10-15 6:51 ` Arthur Schwarz
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