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* Re: c++/4337: [2003-01-01]c++ ignores cast operator
@ 2003-05-14 0:46 Giovanni Bajo
0 siblings, 0 replies; 3+ messages in thread
From: Giovanni Bajo @ 2003-05-14 0:46 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR c++/4337; it has been noted by GNATS.
From: "Giovanni Bajo" <giovannibajo@libero.it>
To: "Bogdanov, Serge" <serge.bogdanov@intel.com>,
<gcc-bugs@gcc.gnu.org>,
<gcc-prs@gcc.gnu.org>,
<nobody@gcc.gnu.org>,
<gcc-gnats@gcc.gnu.org>
Cc:
Subject: Re: c++/4337: [2003-01-01]c++ ignores cast operator
Date: Wed, 14 May 2003 02:36:09 +0200
Bogdanov, Serge <serge.bogdanov@intel.com> wrote:
> The latest analysis by Giovanni solves one mystery, but there is
> another one in the same bug report: if the cast operator is removed,
> compiler produces warnings.
>
>>>> g++ -o a a.cpp
> a.cpp: In function `int main()':
> a.cpp:27: warning: choosing `A2::operator A1()' over `A1::A1(const A&)'
> a.cpp:27: warning: for conversion from `A2' to `A1'
> a.cpp:27: warning: because conversion sequence for the argument is
better
And what would the problem be? If you remove the cast operator, you end up
with "a2 = a1" which obviously selects the cast operator. The compiler is
just warning you about the possible ambiguity, but it's choosing the right
path.
Giovanni Bajo
^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: c++/4337: [2003-01-01]c++ ignores cast operator
@ 2003-05-13 21:19 Bogdanov, Serge
0 siblings, 0 replies; 3+ messages in thread
From: Bogdanov, Serge @ 2003-05-13 21:19 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR c++/4337; it has been noted by GNATS.
From: "Bogdanov, Serge" <serge.bogdanov@intel.com>
To: "'giovannibajo@libero.it'" <giovannibajo@libero.it>,
"'gcc-bugs@gcc.gnu.org'" <gcc-bugs@gcc.gnu.org>,
"'gcc-prs@gcc.gnu.org'"
<gcc-prs@gcc.gnu.org>,
"'nobody@gcc.gnu.org'" <nobody@gcc.gnu.org>,
"Bogdanov, Serge" <serge.bogdanov@intel.com>,
"'gcc-gnats@gcc.gnu.org'"
<gcc-gnats@gcc.gnu.org>
Cc:
Subject: RE: c++/4337: [2003-01-01]c++ ignores cast operator
Date: Tue, 13 May 2003 14:11:50 -0700
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Hi,
=20
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=3Dview%20audittrail&database=3D=
gcc&pr
=3D4337
=20
The latest analysis by Giovanni solves one mystery, but there is
another one in the same bug report: if the cast operator is removed,
compiler produces warnings.
=20
>>> g++ -o a a.cpp
a.cpp: In function `int main()':
a.cpp:27: warning: choosing `A2::operator A1()' over `A1::A1(const A&)'
a.cpp:27: warning: for conversion from `A2' to `A1'
a.cpp:27: warning: because conversion sequence for the argument is =
better
=20
btw, the attempt to use a cast operator was caused by these messages.
Therefore I think that the issue is not closed yet. Please re-open =
it.to use
a cast operator was caused by these messages
=20
I tried it with gcc 3.2.2.
=20
>> Sergey Bogdanov
intel corporation
SHR1-1/S30
334 South Street, Shrewsbury, MA 01745
Tel: (508) 841-1618
=20
-----Original Message-----
From: giovannibajo@libero.it [mailto:giovannibajo@libero.it]=20
Sent: Sunday, May 04, 2003 9:14 PM
To: gcc-bugs@gcc.gnu.org; gcc-prs@gcc.gnu.org; nobody@gcc.gnu.org;
serge.bogdanov@intel.com
Subject: Re: c++/4337: [2003-01-01]c++ ignores cast operator
=20
Synopsis: [2003-01-01]c++ ignores cast operator
=20
State-Changed-From-To: analyzed->closed
State-Changed-By: bajo
State-Changed-When: Mon May 5 01:14:02 2003
State-Changed-Why:
Not a bug. "a1 =3D (A1)a2" is a type conversion in cast=20
notation (=A75.4). "a1 =3D const_cast<A1>(a2)" is=20
ill-formed, but "a1 =3D static_cast<A1>(a2)" is well-formed,
because "a1 =3D A1(a2)" is well-formed (this is the exact
condition specified by =A75.2.9p2). Thus, for =A75.4p5, the
cast notation is equivalent to the static_cast notation.
The static_cast notation is then equivalent to=20
"a1 =3D A1(a2)", which upcasts a2 to const A& implicitally,
and then invokes A1(const A&).=20
G++ behaves exactly as the standard prescribes, and all
the other compilers I have agree.
If you need to force the use of the custom conversion=20
operator, you can still do it using the syntax
"a1 =3D a2.operator A1()".
=20
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=3Dview%20audittrail&database=3D=
gcc&pr
=3D4337
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<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>Hi,</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=3Dview%20audittrail&a=
mp;database=3Dgcc&pr=3D4337</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0=A0=A0 The latest analysis by Giovanni solves one =
mystery, but there is
another one in the same bug report: if the cast operator is removed, =
compiler
produces warnings.</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>>>> g++ -o a a.cpp</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>a.cpp: In function `int main()':</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>a.cpp:27: warning: choosing `A2::operator A1()' over =
`A1::A1(const
A&)'</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>a.cpp:27: warning:=A0=A0 for conversion from `A2' to =
`A1'</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>a.cpp:27: warning:=A0=A0 because conversion sequence for the =
argument is
better</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>btw, the attempt to use a cast operator was caused by these =
messages.
Therefore I think that the issue is not closed yet. Please re-open =
it.<span
style=3D'display:none'>to use a cast operator was caused by these =
messages</span></span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>I tried it with gcc 3.2.2.</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>>> Sergey Bogdanov</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>intel corporation</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>SHR1-1/S30</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>334 South Street, Shrewsbury, MA 01745</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>Tel: (508) 841-1618</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>-----Original Message-----<br>
From: giovannibajo@libero.it [mailto:giovannibajo@libero.it] <br>
Sent: Sunday, May 04, 2003 9:14 PM<br>
To: gcc-bugs@gcc.gnu.org; gcc-prs@gcc.gnu.org; nobody@gcc.gnu.org;
serge.bogdanov@intel.com<br>
Subject: Re: c++/4337: [2003-01-01]c++ ignores cast =
operator</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>Synopsis: [2003-01-01]c++ ignores cast =
operator</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>State-Changed-From-To: analyzed->closed</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>State-Changed-By: bajo</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>State-Changed-When: Mon May=A0 5 01:14:02 =
2003</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>State-Changed-Why:</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 Not a bug. "a1 =3D (A1)a2" is a type =
conversion in cast </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 notation (=A75.4). "a1 =3D =
const_cast<A1>(a2)" is </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 ill-formed, but "a1 =3D =
static_cast<A1>(a2)" is
well-formed,</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 because "a1 =3D A1(a2)" is well-formed =
(this is the exact</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 condition specified by =A75.2.9p2). Thus, for =
=A75.4p5, the</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 cast notation is equivalent to the static_cast =
notation.</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 The static_cast notation is then equivalent to =
</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 "a1 =3D A1(a2)", which upcasts a2 to const =
A&
implicitally,</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 and then invokes A1(const A&). </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 G++ behaves exactly as the standard prescribes, and =
all</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 the other compilers I have agree.</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0 =A0If you need to force the use of the custom conversion =
</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 operator, you can still do it using the =
syntax</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>=A0=A0=A0 "a1 =3D a2.operator =
A1()".</span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'> </span></font></p>
<p class=3DMsoPlainText><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:
10.0pt'>http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=3Dview%20audittrail&a=
mp;database=3Dgcc&pr=3D4337</span></font></p>
</div>
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: c++/4337: [2003-01-01]c++ ignores cast operator
@ 2003-05-05 1:14 giovannibajo
0 siblings, 0 replies; 3+ messages in thread
From: giovannibajo @ 2003-05-05 1:14 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, nobody, serge.bogdanov
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1005 bytes --]
Synopsis: [2003-01-01]c++ ignores cast operator
State-Changed-From-To: analyzed->closed
State-Changed-By: bajo
State-Changed-When: Mon May 5 01:14:02 2003
State-Changed-Why:
Not a bug. "a1 = (A1)a2" is a type conversion in cast
notation (§5.4). "a1 = const_cast<A1>(a2)" is
ill-formed, but "a1 = static_cast<A1>(a2)" is well-formed,
because "a1 = A1(a2)" is well-formed (this is the exact
condition specified by §5.2.9p2). Thus, for §5.4p5, the
cast notation is equivalent to the static_cast notation.
The static_cast notation is then equivalent to
"a1 = A1(a2)", which upcasts a2 to const A& implicitally,
and then invokes A1(const A&).
G++ behaves exactly as the standard prescribes, and all
the other compilers I have agree.
If you need to force the use of the custom conversion
operator, you can still do it using the syntax
"a1 = a2.operator A1()".
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=4337
^ permalink raw reply [flat|nested] 3+ messages in thread
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2003-05-14 0:46 c++/4337: [2003-01-01]c++ ignores cast operator Giovanni Bajo
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2003-05-13 21:19 Bogdanov, Serge
2003-05-05 1:14 giovannibajo
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