Namespaces in C formal definition

I'm reading the N1570 Standard and have a problem to understand the wording of the name space definition. Here is it:

1 If more than one declaration of a particular identifier is visible
at any point in a translation unit, the syntactic context
disambiguates uses that refer to different entities. Thus, there are
separate name spaces for various categories of identifiers, as
follows:

— label names (disambiguated by the syntax of the label
declaration and use);

— the tags of structures, unions, and
enumerations (disambiguated by following any³²⁾ of the keywords
struct, union, or enum);

— the members of structures or unions; each
structure or union has a separate name space for its members
(disambiguated by the type of the expression used to access the member
via the . or -> operator);

— all other identifiers, called ordinary
identifiers (declared in ordinary declarators or as enumeration
constants).

³²⁾ There is only one name space for tags even though three are possible.

Here they are talking about in case of more than 1 declaration of particular identifiers is visible. Now words something like "To access an identifier one shall specify its namespace" or "To access an identifier in a specific namespace...".

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

asked Nov 23 '18 at 7:02

Some Name

830214

1

What's your question? In case you are thinking about C++ namespaces, that's entirely different.
– Nelfeal
Nov 23 '18 at 7:07

@Nelfeal Defnitely not about C++ namespaces. I want to uderstand the percise meaning of namespaces in C and rules how to work with them.
– Some Name
Nov 23 '18 at 7:08

Note that macros cut across all these namespaces indiscriminately, but they've ceased to be an issue by the time these namespaces are discussed. (C11 §6.2.1 Scopes of identifiers ¶1: Macro names and macro parameters are not considered further here, because prior to the semantic phase of program translation any occurrences of macro names in the source file are replaced by the preprocessing token sequences that constitute their macro definitions.)
– Jonathan Leffler
Nov 23 '18 at 7:49

add a comment |

I'm reading the N1570 Standard and have a problem to understand the wording of the name space definition. Here is it:

1 If more than one declaration of a particular identifier is visible
at any point in a translation unit, the syntactic context
disambiguates uses that refer to different entities. Thus, there are
separate name spaces for various categories of identifiers, as
follows:

— label names (disambiguated by the syntax of the label
declaration and use);

— the tags of structures, unions, and
enumerations (disambiguated by following any³²⁾ of the keywords
struct, union, or enum);

— the members of structures or unions; each
structure or union has a separate name space for its members
(disambiguated by the type of the expression used to access the member
via the . or -> operator);

— all other identifiers, called ordinary
identifiers (declared in ordinary declarators or as enumeration
constants).

³²⁾ There is only one name space for tags even though three are possible.

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

asked Nov 23 '18 at 7:02

Some Name

830214

1

What's your question? In case you are thinking about C++ namespaces, that's entirely different.
– Nelfeal
Nov 23 '18 at 7:07

@Nelfeal Defnitely not about C++ namespaces. I want to uderstand the percise meaning of namespaces in C and rules how to work with them.
– Some Name
Nov 23 '18 at 7:08

Note that macros cut across all these namespaces indiscriminately, but they've ceased to be an issue by the time these namespaces are discussed. (C11 §6.2.1 Scopes of identifiers ¶1: Macro names and macro parameters are not considered further here, because prior to the semantic phase of program translation any occurrences of macro names in the source file are replaced by the preprocessing token sequences that constitute their macro definitions.)
– Jonathan Leffler
Nov 23 '18 at 7:49

add a comment |

I'm reading the N1570 Standard and have a problem to understand the wording of the name space definition. Here is it:

1 If more than one declaration of a particular identifier is visible
at any point in a translation unit, the syntactic context
disambiguates uses that refer to different entities. Thus, there are
separate name spaces for various categories of identifiers, as
follows:

— label names (disambiguated by the syntax of the label
declaration and use);

— the tags of structures, unions, and
enumerations (disambiguated by following any³²⁾ of the keywords
struct, union, or enum);

— the members of structures or unions; each
structure or union has a separate name space for its members
(disambiguated by the type of the expression used to access the member
via the . or -> operator);

— all other identifiers, called ordinary
identifiers (declared in ordinary declarators or as enumeration
constants).

³²⁾ There is only one name space for tags even though three are possible.

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

asked Nov 23 '18 at 7:02

Some Name

830214

I'm reading the N1570 Standard and have a problem to understand the wording of the name space definition. Here is it:

1 If more than one declaration of a particular identifier is visible
at any point in a translation unit, the syntactic context
disambiguates uses that refer to different entities. Thus, there are
separate name spaces for various categories of identifiers, as
follows:

— label names (disambiguated by the syntax of the label
declaration and use);

— the tags of structures, unions, and
enumerations (disambiguated by following any³²⁾ of the keywords
struct, union, or enum);

— the members of structures or unions; each
structure or union has a separate name space for its members
(disambiguated by the type of the expression used to access the member
via the . or -> operator);

— all other identifiers, called ordinary
identifiers (declared in ordinary declarators or as enumeration
constants).

³²⁾ There is only one name space for tags even though three are possible.

c namespaces language-lawyer

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

asked Nov 23 '18 at 7:02

Some Name

830214

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

asked Nov 23 '18 at 7:02

Some Name

830214

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

edited Nov 23 '18 at 7:46

Jonathan Leffler

561k896661018

asked Nov 23 '18 at 7:02

Some Name

830214

asked Nov 23 '18 at 7:02

Some Name

830214

asked Nov 23 '18 at 7:02

Some Name

830214

1

What's your question? In case you are thinking about C++ namespaces, that's entirely different.
– Nelfeal
Nov 23 '18 at 7:07

@Nelfeal Defnitely not about C++ namespaces. I want to uderstand the percise meaning of namespaces in C and rules how to work with them.
– Some Name
Nov 23 '18 at 7:08

Note that macros cut across all these namespaces indiscriminately, but they've ceased to be an issue by the time these namespaces are discussed. (C11 §6.2.1 Scopes of identifiers ¶1: Macro names and macro parameters are not considered further here, because prior to the semantic phase of program translation any occurrences of macro names in the source file are replaced by the preprocessing token sequences that constitute their macro definitions.)
– Jonathan Leffler
Nov 23 '18 at 7:49

add a comment |

1

What's your question? In case you are thinking about C++ namespaces, that's entirely different.
– Nelfeal
Nov 23 '18 at 7:07

@Nelfeal Defnitely not about C++ namespaces. I want to uderstand the percise meaning of namespaces in C and rules how to work with them.
– Some Name
Nov 23 '18 at 7:08

Note that macros cut across all these namespaces indiscriminately, but they've ceased to be an issue by the time these namespaces are discussed. (C11 §6.2.1 Scopes of identifiers ¶1: Macro names and macro parameters are not considered further here, because prior to the semantic phase of program translation any occurrences of macro names in the source file are replaced by the preprocessing token sequences that constitute their macro definitions.)
– Jonathan Leffler
Nov 23 '18 at 7:49

What's your question? In case you are thinking about C++ namespaces, that's entirely different.
– Nelfeal
Nov 23 '18 at 7:07

@Nelfeal Defnitely not about C++ namespaces. I want to uderstand the percise meaning of namespaces in C and rules how to work with them.
– Some Name
Nov 23 '18 at 7:08

Note that macros cut across all these namespaces indiscriminately, but they've ceased to be an issue by the time these namespaces are discussed. (C11 §6.2.1 Scopes of identifiers ¶1: Macro names and macro parameters are not considered further here, because prior to the semantic phase of program translation any occurrences of macro names in the source file are replaced by the preprocessing token sequences that constitute their macro definitions.)
– Jonathan Leffler
Nov 23 '18 at 7:49

add a comment |

1 Answer
1

active

oldest

votes

Let me show an example first (this is strictly for understanding purpose, dont write code like this, ever)

#include  <stdio.h>





int main(void)

{

    int here = 0;    //.......................ordinary identifier

    struct here {    //.......................structure tag

        int here;    //.......................member of a structure

    } there;



here:                             //......... a label name

     here++;

     printf("Inside heren");

     there.here = here;           //...........no conflict, both are in separate namespace

     if (here > 2) {

         return 0; 

     }

     else

       goto here;                 //......... a label name



    printf("Hello, world!n");          // control does not reach here..intentionally :)

    return 0;

}

You see usage of identifier here. They belong to separate namespace(s) according to the rule, hence this program is fine.

However, say, for example, you change the structure variable name, from there to here, and you'll see a conflict, as then, there would be two separate declaration of same identifier (ordinary identifier) in the same namespace.

edited Nov 23 '18 at 7:44

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

1

I believe this code is neither here nor there :)
– Lundin
Nov 23 '18 at 7:48

1

@Lundin: It's quantum physical code — it is both here and there.
– Jonathan Leffler
Nov 23 '18 at 7:52

@Lundin It's somewhere, I guess...not count the time factor, either. :)
– Sourav Ghosh
Nov 23 '18 at 7:53

add a comment |

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1 Answer
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1 Answer
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votes

Let me show an example first (this is strictly for understanding purpose, dont write code like this, ever)

#include  <stdio.h>





int main(void)

{

    int here = 0;    //.......................ordinary identifier

    struct here {    //.......................structure tag

        int here;    //.......................member of a structure

    } there;



here:                             //......... a label name

     here++;

     printf("Inside heren");

     there.here = here;           //...........no conflict, both are in separate namespace

     if (here > 2) {

         return 0; 

     }

     else

       goto here;                 //......... a label name



    printf("Hello, world!n");          // control does not reach here..intentionally :)

    return 0;

}

You see usage of identifier here. They belong to separate namespace(s) according to the rule, hence this program is fine.

edited Nov 23 '18 at 7:44

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

1

I believe this code is neither here nor there :)
– Lundin
Nov 23 '18 at 7:48

1

@Lundin: It's quantum physical code — it is both here and there.
– Jonathan Leffler
Nov 23 '18 at 7:52

@Lundin It's somewhere, I guess...not count the time factor, either. :)
– Sourav Ghosh
Nov 23 '18 at 7:53

add a comment |

Let me show an example first (this is strictly for understanding purpose, dont write code like this, ever)

#include  <stdio.h>





int main(void)

{

    int here = 0;    //.......................ordinary identifier

    struct here {    //.......................structure tag

        int here;    //.......................member of a structure

    } there;



here:                             //......... a label name

     here++;

     printf("Inside heren");

     there.here = here;           //...........no conflict, both are in separate namespace

     if (here > 2) {

         return 0; 

     }

     else

       goto here;                 //......... a label name



    printf("Hello, world!n");          // control does not reach here..intentionally :)

    return 0;

}

You see usage of identifier here. They belong to separate namespace(s) according to the rule, hence this program is fine.

edited Nov 23 '18 at 7:44

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

1

I believe this code is neither here nor there :)
– Lundin
Nov 23 '18 at 7:48

1

@Lundin: It's quantum physical code — it is both here and there.
– Jonathan Leffler
Nov 23 '18 at 7:52

@Lundin It's somewhere, I guess...not count the time factor, either. :)
– Sourav Ghosh
Nov 23 '18 at 7:53

add a comment |

Let me show an example first (this is strictly for understanding purpose, dont write code like this, ever)

#include  <stdio.h>





int main(void)

{

    int here = 0;    //.......................ordinary identifier

    struct here {    //.......................structure tag

        int here;    //.......................member of a structure

    } there;



here:                             //......... a label name

     here++;

     printf("Inside heren");

     there.here = here;           //...........no conflict, both are in separate namespace

     if (here > 2) {

         return 0; 

     }

     else

       goto here;                 //......... a label name



    printf("Hello, world!n");          // control does not reach here..intentionally :)

    return 0;

}

You see usage of identifier here. They belong to separate namespace(s) according to the rule, hence this program is fine.

edited Nov 23 '18 at 7:44

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

Let me show an example first (this is strictly for understanding purpose, dont write code like this, ever)

#include  <stdio.h>





int main(void)

{

    int here = 0;    //.......................ordinary identifier

    struct here {    //.......................structure tag

        int here;    //.......................member of a structure

    } there;



here:                             //......... a label name

     here++;

     printf("Inside heren");

     there.here = here;           //...........no conflict, both are in separate namespace

     if (here > 2) {

         return 0; 

     }

     else

       goto here;                 //......... a label name



    printf("Hello, world!n");          // control does not reach here..intentionally :)

    return 0;

}

You see usage of identifier here. They belong to separate namespace(s) according to the rule, hence this program is fine.

edited Nov 23 '18 at 7:44

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

edited Nov 23 '18 at 7:44

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

answered Nov 23 '18 at 7:14

Sourav Ghosh

109k14129187

1

I believe this code is neither here nor there :)
– Lundin
Nov 23 '18 at 7:48

1

@Lundin: It's quantum physical code — it is both here and there.
– Jonathan Leffler
Nov 23 '18 at 7:52

@Lundin It's somewhere, I guess...not count the time factor, either. :)
– Sourav Ghosh
Nov 23 '18 at 7:53

add a comment |

1

I believe this code is neither here nor there :)
– Lundin
Nov 23 '18 at 7:48

1

@Lundin: It's quantum physical code — it is both here and there.
– Jonathan Leffler
Nov 23 '18 at 7:52

@Lundin It's somewhere, I guess...not count the time factor, either. :)
– Sourav Ghosh
Nov 23 '18 at 7:53

I believe this code is neither here nor there :)
– Lundin
Nov 23 '18 at 7:48

@Lundin: It's quantum physical code — it is both here and there.
– Jonathan Leffler
Nov 23 '18 at 7:52

@Lundin It's somewhere, I guess...not count the time factor, either. :)
– Sourav Ghosh
Nov 23 '18 at 7:53

add a comment |

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