Function Pointer declaration and function definition together

c, codeblocks, mingw

Solution

This:

void (*const m_exec[N_EXECS])(void)

is the way you declare an array of function pointers in C. You are not alone in finding this difficult to read. It declares an array of length `N_EXECS`, where each element in the array is a function that takes no arguments and returns a pointer to a const-void.

The braces-enclosed block after it is the array initializer; probably `proclist.h` has a whole list of function pointer declarations in it, and this is essentially pasting those into this array. If you want to see what's actually happening after the `#include`, you can use the `-E` flag of your compiler. So if this were in `main.c`, you would run:

gcc -E -Ipath/to/headers -Iother/path/to/headers main.c

And it would give you a (probably huge) dump of source code, which is the result of pushing that file through the preprocessor and evaluating all of the `#include` statements.

Edit: missed your last question.

Probably (and this is conjecture without seeing `proclist.h`), the things its defining change the contents of `proclist.h`. For example, if it contained:

#ifdef PROCESS_TIMED
&function1_timed,
&function2_timed
#else
&function1,
&function2
#endif

Then `#define PROCESS_TIMED` would change what ended up in your `m_exec` array.

Problem

I saw some piece of code in one of the old files. ``` void (*const m_exec[N_EXECS])(void) = { #define PROCESS_DEF_TIMED(name) name, // defines macro for use in proclist.h #define PROCESS_TIMED // define switch for section in proclist.h #include "proclist.h" #undef PROCESS_TIMED // undefine switch #undef PROCESS_DEF_TIMED // undefines macro }; ``` I am unable to understand the meaning of this code. Is this a function pointer with declaration and function definition together? But if I try to declare similar function pointer like below, I get compilation error ``` void (*voidFptr)(void) = { printf("Hello\n"); } ``` Also what is #define here? Why this is inside the function I am not sure.

Original source