Odd ( ) ( ) C syntax - what does it do

Question

There is the following code declaration:

int (*oled_format)(unsigned short F_gfx, unsigned char* oled_data, size_t oled_len, ...);

used in situations such as below:

format_rc = display_port->dev->oled_format(cmd, oled_data, cmd_len, color);

What does this do? Clearly it returns an int, but there does not seem to be any function description outside of the header file.

Googling brought me to some C++ docs about explicit instantiation which are not very clear and sometimes vary syntactically: 1 , and 2

```oled_format``` is a pointer to a function. [This answer](https://stackoverflow.com/questions/840501/how-do-function-pointers-in-c-work) should be a good overview how those work. — sj95126, Jul 16 '21 at 17:31
This could help you in the future, [cdecl](https://cdecl.org/?q=int+%28*oled_format%29%28unsigned+short%2C+unsigned+char+*%29). — alex01011, Jul 16 '21 at 17:34
Please note that you've linked to C++ references, but C and C++ are different languages so they _will_ vary syntactically. The C resources already listed are much better references in this situation. — Chris, Jul 16 '21 at 19:00

jstedfast · Accepted Answer · 2021-07-16T20:05:19.260

0

It's the declaration of a function pointer.

For those who are interested, the following StackOverflow answer explains how C's function pointers work:

edited Jul 16 '21 at 20:05

answered Jul 16 '21 at 17:32

jstedfast

2

May as well include the link from the comment by @sj95126, at least then your answer would link to further information. – David C. Rankin Jul 16 '21 at 18:36

1 Answers1