Duplicate CV qualifiers
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I have a simple piece of code:
const const int a = 10;
It fails to compile with gcc:
error: duplicate 'const'
However clang compiles it with a warning:
warning: duplicate 'const' declaration specifier [-Wduplicate-decl-specifier]
Microsoft compiler also generates a warning.
Also situation with volatile qualifier is the same.
From the [dcl.type] (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf):
As a general rule, at most one defining-type-specifier is allowed in the complete decl-specifier-seq of a declaration or in a defining-type-specifier-seq, and at most one type-specifier is allowed in a type-specifier-seq.
The only exceptions to this rule are the following:
(2.1)
const can be combined with any type specifier except itself.
(2.2)
volatile can be combined with any type specifier except itself.
(2.3)
signed or unsigned can be combined with char, long, short, or int.
(2.4)
short or long can be combined with int.
(2.5)
long can be combined with double.
(2.6)
long can be combined with long.
So I don't quite understand what does "as a general rule" means. Is this formally valid or not?
Also I found the related issue Duplicate const qualifier allowed in C but not in C++?, but there discussion is mainly about c and c++ differences.
c++ const volatile
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
|
show 4 more comments
I have a simple piece of code:
const const int a = 10;
It fails to compile with gcc:
error: duplicate 'const'
However clang compiles it with a warning:
warning: duplicate 'const' declaration specifier [-Wduplicate-decl-specifier]
Microsoft compiler also generates a warning.
Also situation with volatile qualifier is the same.
From the [dcl.type] (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf):
As a general rule, at most one defining-type-specifier is allowed in the complete decl-specifier-seq of a declaration or in a defining-type-specifier-seq, and at most one type-specifier is allowed in a type-specifier-seq.
The only exceptions to this rule are the following:
(2.1)
const can be combined with any type specifier except itself.
(2.2)
volatile can be combined with any type specifier except itself.
(2.3)
signed or unsigned can be combined with char, long, short, or int.
(2.4)
short or long can be combined with int.
(2.5)
long can be combined with double.
(2.6)
long can be combined with long.
So I don't quite understand what does "as a general rule" means. Is this formally valid or not?
Also I found the related issue Duplicate const qualifier allowed in C but not in C++?, but there discussion is mainly about c and c++ differences.
c++ const volatile
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
Which version of the standard are you quoting from? Which draft?
– Some programmer dude
Nov 22 '18 at 6:48
Get it from eel.is/c++draft/dcl.type. Actually I don't know to what version of the c++ standard it refers to.
– Seleznev Anton
Nov 22 '18 at 6:54
eel.is holds the current tip of the C++ standard working draft. It's not a draft for a published version, but for a future version (C++20).
– StoryTeller
Nov 22 '18 at 6:58
It's probably the latest C++20 draft, but the source directly used to generate the web-pages have commits not part of the C++ standard repository so I'd be a little bit wary of it.
– Some programmer dude
Nov 22 '18 at 7:00
Found open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf for c++17. The same is written there. Updated link in the question.
– Seleznev Anton
Nov 22 '18 at 7:03
|
show 4 more comments
I have a simple piece of code:
const const int a = 10;
It fails to compile with gcc:
error: duplicate 'const'
However clang compiles it with a warning:
warning: duplicate 'const' declaration specifier [-Wduplicate-decl-specifier]
Microsoft compiler also generates a warning.
Also situation with volatile qualifier is the same.
From the [dcl.type] (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf):
As a general rule, at most one defining-type-specifier is allowed in the complete decl-specifier-seq of a declaration or in a defining-type-specifier-seq, and at most one type-specifier is allowed in a type-specifier-seq.
The only exceptions to this rule are the following:
(2.1)
const can be combined with any type specifier except itself.
(2.2)
volatile can be combined with any type specifier except itself.
(2.3)
signed or unsigned can be combined with char, long, short, or int.
(2.4)
short or long can be combined with int.
(2.5)
long can be combined with double.
(2.6)
long can be combined with long.
So I don't quite understand what does "as a general rule" means. Is this formally valid or not?
Also I found the related issue Duplicate const qualifier allowed in C but not in C++?, but there discussion is mainly about c and c++ differences.
c++ const volatile
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
I have a simple piece of code:
const const int a = 10;
It fails to compile with gcc:
error: duplicate 'const'
However clang compiles it with a warning:
warning: duplicate 'const' declaration specifier [-Wduplicate-decl-specifier]
Microsoft compiler also generates a warning.
Also situation with volatile qualifier is the same.
From the [dcl.type] (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf):
As a general rule, at most one defining-type-specifier is allowed in the complete decl-specifier-seq of a declaration or in a defining-type-specifier-seq, and at most one type-specifier is allowed in a type-specifier-seq.
The only exceptions to this rule are the following:
(2.1)
const can be combined with any type specifier except itself.
(2.2)
volatile can be combined with any type specifier except itself.
(2.3)
signed or unsigned can be combined with char, long, short, or int.
(2.4)
short or long can be combined with int.
(2.5)
long can be combined with double.
(2.6)
long can be combined with long.
So I don't quite understand what does "as a general rule" means. Is this formally valid or not?
Also I found the related issue Duplicate const qualifier allowed in C but not in C++?, but there discussion is mainly about c and c++ differences.
c++ const volatile
c++ const volatile
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
edited Nov 22 '18 at 7:48
Seleznev Anton
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
asked Nov 22 '18 at 6:47
Seleznev AntonSeleznev Anton
379213
379213
Which version of the standard are you quoting from? Which draft?
– Some programmer dude
Nov 22 '18 at 6:48
Get it from eel.is/c++draft/dcl.type. Actually I don't know to what version of the c++ standard it refers to.
– Seleznev Anton
Nov 22 '18 at 6:54
eel.is holds the current tip of the C++ standard working draft. It's not a draft for a published version, but for a future version (C++20).
– StoryTeller
Nov 22 '18 at 6:58
It's probably the latest C++20 draft, but the source directly used to generate the web-pages have commits not part of the C++ standard repository so I'd be a little bit wary of it.
– Some programmer dude
Nov 22 '18 at 7:00
Found open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf for c++17. The same is written there. Updated link in the question.
– Seleznev Anton
Nov 22 '18 at 7:03
|
show 4 more comments
Which version of the standard are you quoting from? Which draft?
– Some programmer dude
Nov 22 '18 at 6:48
Get it from eel.is/c++draft/dcl.type. Actually I don't know to what version of the c++ standard it refers to.
– Seleznev Anton
Nov 22 '18 at 6:54
eel.is holds the current tip of the C++ standard working draft. It's not a draft for a published version, but for a future version (C++20).
– StoryTeller
Nov 22 '18 at 6:58
It's probably the latest C++20 draft, but the source directly used to generate the web-pages have commits not part of the C++ standard repository so I'd be a little bit wary of it.
– Some programmer dude
Nov 22 '18 at 7:00
Found open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf for c++17. The same is written there. Updated link in the question.
– Seleznev Anton
Nov 22 '18 at 7:03
Which version of the standard are you quoting from? Which draft?
– Some programmer dude
Nov 22 '18 at 6:48
Which version of the standard are you quoting from? Which draft?
– Some programmer dude
Nov 22 '18 at 6:48
Get it from eel.is/c++draft/dcl.type. Actually I don't know to what version of the c++ standard it refers to.
– Seleznev Anton
Nov 22 '18 at 6:54
Get it from eel.is/c++draft/dcl.type. Actually I don't know to what version of the c++ standard it refers to.
– Seleznev Anton
Nov 22 '18 at 6:54
eel.is holds the current tip of the C++ standard working draft. It's not a draft for a published version, but for a future version (C++20).
– StoryTeller
Nov 22 '18 at 6:58
eel.is holds the current tip of the C++ standard working draft. It's not a draft for a published version, but for a future version (C++20).
– StoryTeller
Nov 22 '18 at 6:58
It's probably the latest C++20 draft, but the source directly used to generate the web-pages have commits not part of the C++ standard repository so I'd be a little bit wary of it.
– Some programmer dude
Nov 22 '18 at 7:00
It's probably the latest C++20 draft, but the source directly used to generate the web-pages have commits not part of the C++ standard repository so I'd be a little bit wary of it.
– Some programmer dude
Nov 22 '18 at 7:00
Found open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf for c++17. The same is written there. Updated link in the question.
– Seleznev Anton
Nov 22 '18 at 7:03
Found open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf for c++17. The same is written there. Updated link in the question.
– Seleznev Anton
Nov 22 '18 at 7:03
|
show 4 more comments
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Which version of the standard are you quoting from? Which draft?
– Some programmer dude
Nov 22 '18 at 6:48
Get it from eel.is/c++draft/dcl.type. Actually I don't know to what version of the c++ standard it refers to.
– Seleznev Anton
Nov 22 '18 at 6:54
eel.is holds the current tip of the C++ standard working draft. It's not a draft for a published version, but for a future version (C++20).
– StoryTeller
Nov 22 '18 at 6:58
It's probably the latest C++20 draft, but the source directly used to generate the web-pages have commits not part of the C++ standard repository so I'd be a little bit wary of it.
– Some programmer dude
Nov 22 '18 at 7:00
Found open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf for c++17. The same is written there. Updated link in the question.
– Seleznev Anton
Nov 22 '18 at 7:03