gcc.info: Initializers

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Non-Constant Initializers

   As in standard C++, the elements of an aggregate initializer for an
automatic variable are not required to be constant expressions in GNU C.
Here is an example of an initializer with run-time varying elements:
     foo (float f, float g)
     {
       float beat_freqs[2] = { f-g, f+g };
       ...
     }