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Function pointer with named arguments?

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9

1

I recently came across a strange syntax in C program.

struct connector_agent_api{

    bool (*receive)(slot *s, uint8_t *data, uint8_t length);

}

Is "receive" a function pointer?

If it is a function pointer, why does it have named arguments? Should it be like the following one?

bool (*receive)(slot *, uint8_t *, uint8_t);

It certainly compiled and being used in a library. I searched on internet a lot and tried to justify this kind of syntax. I still don't know why this thing can be compiled... :(

c function pointers

share|improve this question

edited 1 hour ago

John Kugelman

250k54407461

asked 1 hour ago

ZuckerReisZuckerReis

485

• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  
  These names are for self-documentation only, they have no meaning for the functionality.
  
  – Eugene Sh.
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  Note this is very much like a function declaration in a header file, where parameter names are optional and have no effect on the resulting program.
  
  – jdehesa
  1 hour ago
  

  
  
  
  

add a comment | 

9

1

I recently came across a strange syntax in C program.

struct connector_agent_api{

    bool (*receive)(slot *s, uint8_t *data, uint8_t length);

}

Is "receive" a function pointer?

If it is a function pointer, why does it have named arguments? Should it be like the following one?

bool (*receive)(slot *, uint8_t *, uint8_t);

It certainly compiled and being used in a library. I searched on internet a lot and tried to justify this kind of syntax. I still don't know why this thing can be compiled... :(

c function pointers

share|improve this question

edited 1 hour ago

John Kugelman

250k54407461

asked 1 hour ago

ZuckerReisZuckerReis

485

• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  
  These names are for self-documentation only, they have no meaning for the functionality.
  
  – Eugene Sh.
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  Note this is very much like a function declaration in a header file, where parameter names are optional and have no effect on the resulting program.
  
  – jdehesa
  1 hour ago
  

  
  
  
  

add a comment | 

I recently came across a strange syntax in C program.

struct connector_agent_api{

    bool (*receive)(slot *s, uint8_t *data, uint8_t length);

}

Is "receive" a function pointer?

If it is a function pointer, why does it have named arguments? Should it be like the following one?

bool (*receive)(slot *, uint8_t *, uint8_t);

It certainly compiled and being used in a library. I searched on internet a lot and tried to justify this kind of syntax. I still don't know why this thing can be compiled... :(

c function pointers

share|improve this question

edited 1 hour ago

John Kugelman

250k54407461

asked 1 hour ago

ZuckerReisZuckerReis

485

struct connector_agent_api{

    bool (*receive)(slot *s, uint8_t *data, uint8_t length);

}

bool (*receive)(slot *, uint8_t *, uint8_t);

share|improve this question

edited 1 hour ago

John Kugelman

250k54407461

asked 1 hour ago

ZuckerReisZuckerReis

485

share|improve this question

edited 1 hour ago

John Kugelman

250k54407461

asked 1 hour ago

ZuckerReisZuckerReis

485

edited 1 hour ago

John Kugelman

250k54407461

edited 1 hour ago

John Kugelman

250k54407461

asked 1 hour ago

ZuckerReisZuckerReis

485

asked 1 hour ago

ZuckerReisZuckerReis

485

2 Answers
2

active

oldest

votes

8

The names of arguments in a function pointer are optional, just as the names of arguments in a function declaration are optional. This is because parameter names if given are not used, so both formats are allowed.

The only place where function parameters require a name is in the actual definition of a function.

In section 6.7.6.3 of the C standard regarding Function Declarators, which includes both function prototypes and function pointers, paragraph 6 states:

A parameter type list specifies the types of, and may
declare identifiers for, the parameters of the function.

For a function definition, Section 6.9.1p5 states:

If the declarator includes a parameter type list, the
declaration of each parameter shall include an identifier, except
for the special case of a parameter list consisting of a single
parameter of type void , in which case there shall not be an
identifier. No declaration list shall follow.

share|improve this answer

edited 25 mins ago

answered 1 hour ago

dbushdbush

105k14110148

add a comment | 

1

What makes you think it is a strange syntax? It is a valid declaration as per C standard. The fact that the parameters are named is irrelevant. The naming of such parameters is optional in this case. It can be really helpful if you or someone else is using an IDE because it could display the complete prototype upon using the function pointer to call the function and thus give a hint to the coder about the arguments to be supplied.

share|improve this answer

answered 1 hour ago

machine_1machine_1

2,65521332

add a comment | 

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8

The names of arguments in a function pointer are optional, just as the names of arguments in a function declaration are optional. This is because parameter names if given are not used, so both formats are allowed.

The only place where function parameters require a name is in the actual definition of a function.

In section 6.7.6.3 of the C standard regarding Function Declarators, which includes both function prototypes and function pointers, paragraph 6 states:

A parameter type list specifies the types of, and may
declare identifiers for, the parameters of the function.

For a function definition, Section 6.9.1p5 states:

If the declarator includes a parameter type list, the
declaration of each parameter shall include an identifier, except
for the special case of a parameter list consisting of a single
parameter of type void , in which case there shall not be an
identifier. No declaration list shall follow.

share|improve this answer

edited 25 mins ago

answered 1 hour ago

dbushdbush

105k14110148

add a comment | 

8

The names of arguments in a function pointer are optional, just as the names of arguments in a function declaration are optional. This is because parameter names if given are not used, so both formats are allowed.

The only place where function parameters require a name is in the actual definition of a function.

In section 6.7.6.3 of the C standard regarding Function Declarators, which includes both function prototypes and function pointers, paragraph 6 states:

A parameter type list specifies the types of, and may
declare identifiers for, the parameters of the function.

For a function definition, Section 6.9.1p5 states:

If the declarator includes a parameter type list, the
declaration of each parameter shall include an identifier, except
for the special case of a parameter list consisting of a single
parameter of type void , in which case there shall not be an
identifier. No declaration list shall follow.

share|improve this answer

edited 25 mins ago

answered 1 hour ago

dbushdbush

105k14110148

add a comment | 

The names of arguments in a function pointer are optional, just as the names of arguments in a function declaration are optional. This is because parameter names if given are not used, so both formats are allowed.

The only place where function parameters require a name is in the actual definition of a function.

In section 6.7.6.3 of the C standard regarding Function Declarators, which includes both function prototypes and function pointers, paragraph 6 states:

A parameter type list specifies the types of, and may
declare identifiers for, the parameters of the function.

For a function definition, Section 6.9.1p5 states:

If the declarator includes a parameter type list, the
declaration of each parameter shall include an identifier, except
for the special case of a parameter list consisting of a single
parameter of type void , in which case there shall not be an
identifier. No declaration list shall follow.

share|improve this answer

edited 25 mins ago

answered 1 hour ago

dbushdbush

105k14110148

share|improve this answer

edited 25 mins ago

answered 1 hour ago

dbushdbush

105k14110148

answered 1 hour ago

dbushdbush

105k14110148

answered 1 hour ago

dbushdbush

105k14110148

1

What makes you think it is a strange syntax? It is a valid declaration as per C standard. The fact that the parameters are named is irrelevant. The naming of such parameters is optional in this case. It can be really helpful if you or someone else is using an IDE because it could display the complete prototype upon using the function pointer to call the function and thus give a hint to the coder about the arguments to be supplied.

share|improve this answer

answered 1 hour ago

machine_1machine_1

2,65521332

add a comment | 

1

What makes you think it is a strange syntax? It is a valid declaration as per C standard. The fact that the parameters are named is irrelevant. The naming of such parameters is optional in this case. It can be really helpful if you or someone else is using an IDE because it could display the complete prototype upon using the function pointer to call the function and thus give a hint to the coder about the arguments to be supplied.

share|improve this answer

answered 1 hour ago

machine_1machine_1

2,65521332

add a comment | 

What makes you think it is a strange syntax? It is a valid declaration as per C standard. The fact that the parameters are named is irrelevant. The naming of such parameters is optional in this case. It can be really helpful if you or someone else is using an IDE because it could display the complete prototype upon using the function pointer to call the function and thus give a hint to the coder about the arguments to be supplied.

share|improve this answer

answered 1 hour ago

machine_1machine_1

2,65521332

share|improve this answer

answered 1 hour ago

machine_1machine_1

2,65521332

answered 1 hour ago

machine_1machine_1

2,65521332

answered 1 hour ago

machine_1machine_1

2,65521332