Why isn't the compiler flashing any error?

This is my code:

int a1[][3]={{1,2,3,4,5,6},{4,5,6,5}};

int (*q)[3];

q=a1;

q is a pointer to an array of 3 integers. But a1 does not comply with 开发者_如何学JAVAq's type. Yet the assignment works and no error comes.

Can anyone explain why?

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The types do comply. a1 is an array of length-3 arrays of ints. q is a pointer to a length-3 array of ints. An array decays to a pointer in most circumstances; this is one of them, so everything's fine!

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See the C faq on arrays and pointers. Specifically, Question 6.2.

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The types are equvalent - when you use a1 in the assignment statement it turns into a pointer, and presto - matching types.

Lots more information:

http://c-faq.com/aryptr/index.html

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You are assigning the address of the first element of a1 to the pointer q.