What is this C syntax (used in Linux drivers/net/bonding/bond_main.c)?

I've written plenty of C before, but I don't recognize this syntax:

static const char *names[] = {
[BOND_MODE_ROUNDROBIN] = "load balancing (round-robin)",
[BOND_MODE_ACTIVEBACKUP] = "fault-tolerance (active-backup)",
[BOND_MODE_XOR] = "load balancing (xor)",
[BOND_MODE_BROADCAST] = "fault-tolerance (broadcast)",
[BOND_MODE_8023AD] = "IEEE 802.3ad Dynamic link aggregation",
[BOND_MODE_TLB] = "transmit load balancing",
[BOND_MODE_ALB] = "adaptive load balancing",
};

The `[...] = ` part is what looks weird to me. (By the way, `BOND_MODE_ROUNDROBIN` and the others are macros which just expand to integers.)

That is a <a href="https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html">**designated initializer**</a>. It allows you to intialize the contents of the array in an arbitrary order.

Here names is the array of char pointes.


These pointers are pointing to the string stored in read only section.

And Initilizing is done using **Designated Initializers** methods.

SO here you can initilize any array with any order of their index.
Those macros are index of array.

It's called **designated initializers**, which is introduced in C99. GCC also supports it as an extension.

It's used to initialize structures and arrays, see [Designated Initializers][1] for detail.

[1]:

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