C - Designated Initializer (xv6)

Question

I'm recently taking Operating System course, where we study xv6. During practice lab I ran into the code like below:

// xv6_public/syscall.c
#include "defs.h"
#include "syscalls.h"
...

extern int sys_fork(void);

...

static int (*syscalls[])(void) = {
    [SYS_fork]    sys_fork,
    ...
};

I didn't recognize the syntax used above at all at first. After searching the net I found that the syntax is called Lambda function, but I still have questions:

Many articles say it is available to use Lambda only with C++. Is it able to use Lambda in C? Is syntax the same as that of C++? (the source files are all .c, probably compiler is g++)
Would someone briefly explain the code above? I can understand that it is function pointer array where each element is lambda function. Or please recommend nice reference to read.

And that's not valid lambda syntax. Missing parameter list and body. — Mat, Mar 27 '20 at 08:26

score 2 · Accepted Answer · answered Mar 27 '20 at 08:27

2

That's not C++ lambdas, instead it's standard C99 array initialization using designated initializers.

The value inside the square brackets (e.g. [SYS_fork]) is a compile-time integer constant and designates the index in the array for the initialization.

answered Mar 27 '20 at 08:27

Some programmer dude

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C - Designated Initializer (xv6)

1 Answers1