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Q&A Are these two function pointer declarations equivalent?

Say I have two functions: FILE* get_input(const char fname[static 1]); FILE* get_output(const char fname[static 1]); And I wish to declare a function pointer and assign it the result of some p...

1 answer  ·  posted 6mo ago by Melkor-1‭  ·  edited 6mo ago by Melkor-1‭

Question c c23 typeof
#5: Post edited by user avatar Melkor-1‭ · 2024-06-25T12:00:30Z (6 months ago)
  • Say I have two functions:
  • ```c
  • FILE* get_input(const char fname[static 1]);
  • FILE* get_output(const char fname[static 1]);
  • ```
  • And I wish to declare a function pointer and assign it the result of some processing which shall be called later.
  • Are these two declarations:
  • ```c
  • int (*operation)(FILE*, FILE*);
  • typeof (foo) *op;
  • ```
  • equivalent? Or is there any difference between the types of operation and op? If so, how do I properly declare a function pointer with `typeof`?
  • Say I have two functions:
  • ```c
  • FILE* get_input(const char fname[static 1]);
  • FILE* get_output(const char fname[static 1]);
  • ```
  • And I wish to declare a function pointer and assign it the result of some processing which shall be called later.
  • Are these two declarations:
  • ```c
  • int foo(FILE *, FILE *);
  • int (*operation)(FILE *, FILE *);
  • typeof (foo) *op;
  • ```
  • equivalent? Or is there any difference between the types of operation and op? If so, how do I properly declare a function pointer with `typeof`?
#4: Post edited by user avatar Lundin‭ · 2024-06-25T09:47:09Z (6 months ago)
  • Say I have two functions:
  • ```c
  • FILE* get_input(const char fname[static 1]);
  • FILE* get_output(const char fname[static 1]);
  • ```
  • And I wish to declare a function pointer and assign it the result of some processing which shall be called later.
  • Are these two declarations:
  • ```c
  • I have:
  • ```c
  • int (*operation)(FILE*, FILE*);
  • typeof (foo) *op;
  • ```
  • equivalent? Or is there any difference between the types of operation and op? If so, how do I properly declare a function pointer with `typeof`?
  • Say I have two functions:
  • ```c
  • FILE* get_input(const char fname[static 1]);
  • FILE* get_output(const char fname[static 1]);
  • ```
  • And I wish to declare a function pointer and assign it the result of some processing which shall be called later.
  • Are these two declarations:
  • ```c
  • int (*operation)(FILE*, FILE*);
  • typeof (foo) *op;
  • ```
  • equivalent? Or is there any difference between the types of operation and op? If so, how do I properly declare a function pointer with `typeof`?
#3: Post edited by user avatar Melkor-1‭ · 2024-06-25T08:25:29Z (6 months ago)
  • Say I have two functions:
  • ```c
  • FILE* get_input(const char* fname[static 1]);
  • FILE* get_output(const char* fname[static 1]);
  • ```
  • And I wish to declare a function pointer and assign it the result of some processing which shall be called later.
  • Are these two declarations:
  • ```c
  • I have:
  • ```c
  • int (*operation)(FILE*, FILE*);
  • typeof (foo) *op;
  • ```
  • equivalent? Or is there any difference between the types of operation and op? If so, how do I properly declare a function pointer with `typeof`?
  • Say I have two functions:
  • ```c
  • FILE* get_input(const char fname[static 1]);
  • FILE* get_output(const char fname[static 1]);
  • ```
  • And I wish to declare a function pointer and assign it the result of some processing which shall be called later.
  • Are these two declarations:
  • ```c
  • I have:
  • ```c
  • int (*operation)(FILE*, FILE*);
  • typeof (foo) *op;
  • ```
  • equivalent? Or is there any difference between the types of operation and op? If so, how do I properly declare a function pointer with `typeof`?
#2: Post edited by user avatar Melkor-1‭ · 2024-06-25T08:25:09Z (6 months ago)
  • I have:
  • ```c
  • int foo(FILE *, FILE *);
  • int (*operation)(FILE*, FILE*);
  • typeof (foo) *op;
  • ```
  • Is there any difference between the types of `operation` and `op`? Can I use them interchangably?
  • Say I have two functions:
  • ```c
  • FILE* get_input(const char* fname[static 1]);
  • FILE* get_output(const char* fname[static 1]);
  • ```
  • And I wish to declare a function pointer and assign it the result of some processing which shall be called later.
  • Are these two declarations:
  • ```c
  • I have:
  • ```c
  • int (*operation)(FILE*, FILE*);
  • typeof (foo) *op;
  • ```
  • equivalent? Or is there any difference between the types of operation and op? If so, how do I properly declare a function pointer with `typeof`?
#1: Initial revision by user avatar Melkor-1‭ · 2024-06-25T08:20:06Z (6 months ago)
Are these two function pointer declarations equivalent?
I have:

```c
int foo(FILE *, FILE *);

int (*operation)(FILE*, FILE*);
typeof (foo) *op;
```

Is there any difference between the types of `operation` and `op`? Can I use them interchangably?