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Bill Clarke
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 Posted: Mon Sep 13, 2004 9:53 am Post subject: repeated typedefs |
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My reading of the standard is (and g++ 3.4.0 agrees with me) that the
following is entirely legal:
"""
typedef int Int;
typedef int Int;
namespace B {
typedef int IntB;
typedef int IntB;
}
class A {
void foo() {
typedef int Intfoo;
typedef int Intfoo;
}
typedef int IntA;
typedef int IntA;
};
"""
However, Comeau's online compiler rejects the redefinition of IntA
(coincidently, so does Sun's compiler Sun Studio 9, but it's no fine
example of C++ standard compliance).
C++ standard 7.1.3 (dcl.typedef) paragraph 2 seems to apply here.
"""
2 In a given scope, a typedef specifier can be used to redefine the name
of any type declared in that scope to refer to the type to which it
already refers. [Example:
typedef struct s { /* ... */ } s;
typedef int I;
typedef int I;
typedef I I;
--end example]
"""
Is there anything else that applies here?
cheers,
/lib
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Ben Hutchings
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| Posted: Mon Sep 13, 2004 12:17 pm Post subject: Re: repeated typedefs |
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Bill Clarke wrote:
| Quote: | My reading of the standard is (and g++ 3.4.0 agrees with me) that the
following is entirely legal:
snip
class A {
void foo() {
typedef int Intfoo;
typedef int Intfoo;
}
typedef int IntA;
typedef int IntA;
};
"""
However, Comeau's online compiler rejects the redefinition of IntA
(coincidently, so does Sun's compiler Sun Studio 9, but it's no fine
example of C++ standard compliance).
C++ standard 7.1.3 (dcl.typedef) paragraph 2 seems to apply here.
"""
2 In a given scope, a typedef specifier can be used to redefine the name
of any type declared in that scope to refer to the type to which it
already refers. [Example:
typedef struct s { /* ... */ } s;
typedef int I;
typedef int I;
typedef I I;
--end example]
"""
Is there anything else that applies here?
|
Class scopes are special. From 9.2 paragraph 1:
"A member shall not be be declared twice in the /member-
specification/, except that a nested class or member class
template can be declared and then later defined."
--
Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
- Albert Camus
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Greg Comeau
Guest
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| Posted: Tue Sep 14, 2004 3:18 am Post subject: Re: repeated typedefs |
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In article <b2dfb7d8.0409130012.1dde5ab7 (AT) posting (DOT) google.com>,
Bill Clarke <llib (AT) computer (DOT) org> wrote:
| Quote: | My reading of the standard is (and g++ 3.4.0 agrees with me) that the
following is entirely legal:
"""
typedef int Int;
typedef int Int;
namespace B {
typedef int IntB;
typedef int IntB;
}
class A {
void foo() {
typedef int Intfoo;
typedef int Intfoo;
}
typedef int IntA;
typedef int IntA;
};
"""
However, Comeau's online compiler rejects the redefinition of IntA
(coincidently, so does Sun's compiler Sun Studio 9, but it's no fine
example of C++ standard compliance).
|
Well, AFAICrecall, this rule's been the same for a very long time, so..
| Quote: | C++ standard 7.1.3 (dcl.typedef) paragraph 2 seems to apply here.
"""
2 In a given scope, a typedef specifier can be used to redefine the name
of any type declared in that scope to refer to the type to which it
already refers. [Example:
typedef struct s { /* ... */ } s;
typedef int I;
typedef int I;
typedef I I;
--end example]
"""
Is there anything else that applies here?
|
9.2p1: "...Members of a class are ... nested types, and ....
...Nested types are... arbitrary types declared as members by
use of a typedef declaration .... A member shall not be declared
twice in the member-specification...."
--
Greg Comeau / Comeau C++ 4.3.3, for C++03 core language support
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?
---
[ comp.std.c++ is moderated. To submit articles, try just posting with ]
[ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ]
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Bill Clarke
Guest
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| Posted: Tue Sep 14, 2004 4:06 am Post subject: Re: repeated typedefs |
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Ben Hutchings wrote, On 13/09/04 22:17:
| Quote: | Bill Clarke wrote:
[...]
class A {
[...]
typedef int IntA;
typedef int IntA;
};
"""
[...]
C++ standard 7.1.3 (dcl.typedef) paragraph 2 seems to apply here.
"""
2 In a given scope, a typedef specifier can be used to redefine the
name
of any type declared in that scope to refer to the type to which
it
already refers. [Example:
typedef struct s { /* ... */ } s;
typedef int I;
typedef int I;
typedef I I;
--end example]
"""
Is there anything else that applies here?
Class scopes are special. From 9.2 paragraph 1:
"A member shall not be be declared twice in the /member-
specification/, except that a nested class or member class
template can be declared and then later defined."
|
Okay, I'll accept that (bug report submitted to gcc: PR 17473).
However, 7.1.3/2 is so unequivocal that perhaps there should be a note
pointing to 9.2/1 regarding class scopes.
In addition, it seems plain weird to have an exception for
class-scopes, when other scopes that have equally no reason for
allowing redefinitions are allowed (namely, function scopes).
cheers,
/lib
---
[ comp.std.c++ is moderated. To submit articles, try just posting with ]
[ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ]
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Greg Comeau
Guest
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| Posted: Tue Sep 14, 2004 4:22 pm Post subject: Re: repeated typedefs |
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|
In article <b2dfb7d8.0409131832.b7726bd (AT) posting (DOT) google.com>,
Bill Clarke <llib (AT) computer (DOT) org> wrote:
| Quote: | However, 7.1.3/2 is so unequivocal that perhaps there should be a note
pointing to 9.2/1 regarding class scopes.
|
Probably.
| Quote: | In addition, it seems plain weird to have an exception for
class-scopes, when other scopes that have equally no reason for
allowing redefinitions are allowed (namely, function scopes).
|
C doesn't allow (at least some of) the other cases, so in an odd twist,
it's the other cases which became the (allowed) exceptions.
--
Greg Comeau / Comeau C++ 4.3.3, for C++03 core language support
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?
---
[ comp.std.c++ is moderated. To submit articles, try just posting with ]
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