6.6.4.1.12 -Wmissing-braces

Warn if an aggregate or union initializer is not fully bracketed. In the following example, the initializer for a is not fully bracketed, but that for b is fully bracketed.

int a[2][2] = { 0, 1, 2, 3 };

int b[2][2] = { { 0, 1 }, { 2, 3 } };